Materiały źródłowe

• #1 Microscopic Colitis: Pathogenesis and Diagnosis

  https://pmc.ncbi.nlm.nih.gov/articles/PMC10342440/

  To date, the pathogenesis of microscopic colitis remains unknown and is likely complex and multifactorial. The possible mechanisms include intraluminal factors, such as abnormal microbiota, genetic predisposition, bile acids, and autoimmunity, which could trigger chronic inflammation. […] The role that genetics have in the pathogenesis of microscopic colitis is not completely understood. It has been proposed that microscopic colitis is the result of an abnormal immune response to luminal antigens in genetically predisposed individuals. […] The gut microbiome is another factor that may have implications in the pathogenesis of microscopic colitis. […] Autoimmunity is a possible pathophysiological mechanism in microscopic colitis. […] The association between bile acid malabsorption and microscopic colitis remains poorly understood and is complicated by the complex physiology and metabolism of bile acids in the intestinal tract. […] The pathogenesis of bile acid malabsorption in patients with microscopic colitis likely has several mechanisms.

• #2 Microscopic Colitis: Epidemiology, Pathophysiology, Diagnosis and Current Management—An Update 2013

  https://pmc.ncbi.nlm.nih.gov/articles/PMC3654232/

  Microscopic colitis is an inflammatory disease of the intestine and thus it is regarded as being a new member of the group of inflammatory bowel disease (IBD) […] The pathophysiology of microscopic colitis is still unknown but there is strong evidence that microscopic colitis is frequently associated with the use of certain medications and certain systemic disorders (such as autoimmune and rheumatic disease). […] Nowadays we know that the inflammatory changes are closely related to the symptom chronic diarrhea though there are still plenty of unanswered questions like what causes the specific microscopic changes, are the microscopic changes primary pathogenetic changes or secondary changes, and the burning question: what is the exact mechanism that causes diarrhea, when the mucosa is inflamed?

• #3 Microscopic Colitis: Pathogenesis and Diagnosis

  https://www.mdpi.com/2077-0383/12/13/4442

  Microscopic colitis is an inflammatory bowel disease possibly caused by a chronic immune-mediated process. The pathogenesis of microscopic colitis remains unknown and is likely complex and multifactorial. The possible mechanisms include intraluminal factors, such as abnormal microbiota, genetic predisposition, bile acids, and autoimmunity, which could trigger chronic inflammation. To date, the pathogenesis of microscopic colitis remains unknown and is likely complex and multifactorial. The role that genetics have in the pathogenesis of microscopic colitis is not completely understood. It has been proposed that microscopic colitis is the result of an abnormal immune response to luminal antigens in genetically predisposed individuals. The gut microbiome is another factor that may have implications in the pathogenesis of microscopic colitis. Autoimmunity is a possible pathophysiological mechanism in microscopic colitis. The association between bile acid malabsorption and microscopic colitis remains poorly understood and is complicated by the complex physiology and metabolism of bile acids in the intestinal tract. The pathogenesis of bile acid malabsorption in patients with microscopic colitis likely has several mechanisms. In summary, these studies indicate that bile acids may have a primary or secondary effect in microscopic colitis.

• #4 Microscopic Colitis: Epidemiology, Pathophysiology, Diagnosis and Current Management—An Update 2013

  https://pmc.ncbi.nlm.nih.gov/articles/PMC3654232/

  Microscopic colitis is an inflammatory disease of the intestine and thus it is regarded as being a new member of the group of inflammatory bowel disease (IBD) […] The pathophysiology of microscopic colitis is still unknown but there is strong evidence that microscopic colitis is frequently associated with the use of certain medications and certain systemic disorders (such as autoimmune and rheumatic disease). […] Nowadays we know that the inflammatory changes are closely related to the symptom chronic diarrhea though there are still plenty of unanswered questions like what causes the specific microscopic changes, are the microscopic changes primary pathogenetic changes or secondary changes, and the burning question: what is the exact mechanism that causes diarrhea, when the mucosa is inflamed?

• #5 Microscopic colitis: Common cause of unexplained nonbloody diarrhea

  https://www.wjgnet.com/2150-5330/full/v5/i1/48.htm

  Microscopic colitis (MC) is characterized by chronic, watery, secretory diarrhea, with a normal or near normal gross appearance of the colonic mucosa. […] The etiology of MC is most likely multifactorial with a mucosal inflammatory response to yet not specified noxious luminal agent occurring in a predisposed host. […] Technically, MC is an inflammatory bowel disease (IBD) and the disease shares a number of etiological aspects with the so-called classical inflammatory bowel diseases like Crohns disease and ulcerative colitis. […] Very strong evidence exists for an autoimmune basis to the development of both collagenous and lymphocytic colitis. […] The association of MC with autoimmune-based disorders such as celiac, thyroid disease and rheumatoid arthritis, as well as the female preponderance, supports the notion that both forms of MC have a strong association with autoimmune diseases and may well be an autoimmune disorder themselves.

• #6 Microscopic Colitis: Pathogenesis and Diagnosis

  https://pmc.ncbi.nlm.nih.gov/articles/PMC10342440/

  To date, the pathogenesis of microscopic colitis remains unknown and is likely complex and multifactorial. The possible mechanisms include intraluminal factors, such as abnormal microbiota, genetic predisposition, bile acids, and autoimmunity, which could trigger chronic inflammation. […] The role that genetics have in the pathogenesis of microscopic colitis is not completely understood. It has been proposed that microscopic colitis is the result of an abnormal immune response to luminal antigens in genetically predisposed individuals. […] The gut microbiome is another factor that may have implications in the pathogenesis of microscopic colitis. […] Autoimmunity is a possible pathophysiological mechanism in microscopic colitis. […] The association between bile acid malabsorption and microscopic colitis remains poorly understood and is complicated by the complex physiology and metabolism of bile acids in the intestinal tract. […] The pathogenesis of bile acid malabsorption in patients with microscopic colitis likely has several mechanisms.

• #7 Microscopic Colitis: Pathogenesis and Diagnosis

  https://www.mdpi.com/2077-0383/12/13/4442

  Microscopic colitis is an inflammatory bowel disease possibly caused by a chronic immune-mediated process. The pathogenesis of microscopic colitis remains unknown and is likely complex and multifactorial. The possible mechanisms include intraluminal factors, such as abnormal microbiota, genetic predisposition, bile acids, and autoimmunity, which could trigger chronic inflammation. To date, the pathogenesis of microscopic colitis remains unknown and is likely complex and multifactorial. The role that genetics have in the pathogenesis of microscopic colitis is not completely understood. It has been proposed that microscopic colitis is the result of an abnormal immune response to luminal antigens in genetically predisposed individuals. The gut microbiome is another factor that may have implications in the pathogenesis of microscopic colitis. Autoimmunity is a possible pathophysiological mechanism in microscopic colitis. The association between bile acid malabsorption and microscopic colitis remains poorly understood and is complicated by the complex physiology and metabolism of bile acids in the intestinal tract. The pathogenesis of bile acid malabsorption in patients with microscopic colitis likely has several mechanisms. In summary, these studies indicate that bile acids may have a primary or secondary effect in microscopic colitis.

• #8 Microscopic colitis: Etiopathology, diagnosis, and rational management | eLife

  https://elifesciences.org/articles/79397

  The de-enrichment of Akkermansia muciniphila was additionally observed in a study using PCR. […] More recently, a team of researchers found a higher long-term risk of developing microscopic colitis in patients whose stool carried Campylobacter concisus. […] Campylobacter concisus is associated with epithelial sodium channel dysfunction and claudin-8-dependent barrier dysfunction, suggesting their involvement in the pathogenesis of microscopic colitis. […] Notably, the intake of PPI and smoking influences bacterial flora, especially the former may especially increase the abundance of oral microbes, such as C. concisus, suggesting that dysbiosis may be the mechanism by which these factors cause microscopic colitis. […] A genetic component is of importance as well, and a recent genetic immunochip study reported an association between the human leukocyte antigen (HLA) ancestral 8.1 haplotype and well-established collagenous colitis but not with lymphocytic colitis.

• #9 Microscopic colitis: Etiopathology, diagnosis, and rational management | eLife

  https://elifesciences.org/articles/79397

  The findings supported the role of HLA class I- and II-related mechanisms and identified potential non-HLA alleles linked to the pathogenesis of collagenous colitis. […] The aforementioned findings support the role of HLA class I- and II-related mechanisms and identified potential non-HLA alleles linked to the pathogenesis of collagenous colitis.

• #10 Microscopic Colitis (Collagenous and Lymphocytic Colitis): Background, Pathophysiology, Etiology

  https://emedicine.medscape.com/article/180664-overview

  The pathogenesis of microscopic colitis (MC) is not clearly understood. The etiology is likely multifactorial, potentially including luminal factors, immune dysregulation, and genetic predisposition. […] It may be mediated in part by the adaptive immune system and by cytotoxic responses triggered by mucosal injury from different factors. […] Some studies have also shown an association between microscopic colitis and human leukocyte antigen (HLA)-DQ, as noted in celiac disease. […] A positive correlation between DQ2/DQ8 alleles and lymphocytic colitis (LC) has been noted in some studies. The odds ratio of lymphocytic colitis with positive DQ2-alleles has been found to be as high as 3. […] Another significant association has been observed between 5-HTTLPR (serotonin-transporter-linked polymorphic region) polymorphism and microscopic colitis. 5-HT (serotonin) plays a significant role in regulating intestinal motility and secretion.

• #11 Prevalence, Pathogenesis, Diagnosis, and Management of Microscopic Colitis

  https://www.gutnliver.org/journal/view.html?doi=10.5009/gnl17061

  A luminal component is supported as observation of a small number of patients who have undergone a diverting ileostomy demonstrate histologic improvement in their MC, which returns upon reconnection and resumption of the fecal stream. […] Exposure to a luminal antigen (medication, dietary, bile salts, bacteria) may cause an inflammatory cascade due to activation of CD8 T suppressor cells that may directly attack and damage the enterocyte. […] There is a proposed association between MC and celiac disease (CD), with an increased risk of 50- to 70-fold compared to the general population. […] CD is associated with the human leukocyte antigen (HLA) class II genes, particularly HLA DQ2 and HLA DQ8 alleles. […] The presence of HLA DQ2 types was also described in an additional study of 80 patients with MC (29 CC, 51 LC).

• #12 Prevalence, Pathogenesis, Diagnosis, and Management of Microscopic Colitis

  https://www.gutnliver.org/journal/view.html?doi=10.5009/gnl17061

  Ultimately authors conclude there is an association with the HLA-DR3-DQ2 haplotype with CC and LC in patients with MC with and without CD. […] The diagnosis of MC involves the combination of clinical presentation with histologic changes. […] It is a combination of histologic changes with the proper clinical context that helps the pathologist to make the diagnosis histologically; however, histologic findings are not validated nor pathognomonic.

• #13 Microscopic Colitis (Collagenous and Lymphocytic Colitis): Background, Pathophysiology, Etiology

  https://emedicine.medscape.com/article/180664-overview

  The pathogenesis of microscopic colitis (MC) is not clearly understood. The etiology is likely multifactorial, potentially including luminal factors, immune dysregulation, and genetic predisposition. […] It may be mediated in part by the adaptive immune system and by cytotoxic responses triggered by mucosal injury from different factors. […] Some studies have also shown an association between microscopic colitis and human leukocyte antigen (HLA)-DQ, as noted in celiac disease. […] A positive correlation between DQ2/DQ8 alleles and lymphocytic colitis (LC) has been noted in some studies. The odds ratio of lymphocytic colitis with positive DQ2-alleles has been found to be as high as 3. […] Another significant association has been observed between 5-HTTLPR (serotonin-transporter-linked polymorphic region) polymorphism and microscopic colitis. 5-HT (serotonin) plays a significant role in regulating intestinal motility and secretion.

• #14 Microscopic Colitis (Collagenous and Lymphocytic Colitis): Background, Pathophysiology, Etiology

  https://emedicine.medscape.com/article/180664-overview

  Serotonin levels have been found to be high in patients with microscopic colitis and ulcerative colitis (UC), suggesting a possible association in its pathogenesis. […] The interleukin (IL)-6-174 gene polymorphism also has a possible association with microscopic colitis by influencing the inflammation pathway. IL-6 promotes T- and B-lymphocyte maturation and also contributes to macrophage recruitment, causing acute to chronic immune responses and to differentiation of Th2 and Th17 lymphocytes.

• #15 Microscopic Colitis (Collagenous and Lymphocytic Colitis): Background, Pathophysiology, Etiology

  https://emedicine.medscape.com/article/180664-overview

  Serotonin levels have been found to be high in patients with microscopic colitis and ulcerative colitis (UC), suggesting a possible association in its pathogenesis. […] The interleukin (IL)-6-174 gene polymorphism also has a possible association with microscopic colitis by influencing the inflammation pathway. IL-6 promotes T- and B-lymphocyte maturation and also contributes to macrophage recruitment, causing acute to chronic immune responses and to differentiation of Th2 and Th17 lymphocytes.

• #16 Microscopic Colitis: Epidemiology, Pathophysiology, Diagnosis and Current Management—An Update 2013

  https://pmc.ncbi.nlm.nih.gov/articles/PMC3654232/

  The etiology of microscopic is most likely multifactorial with a mucosal inflammatory response to yet not specified noxious luminal agent occurring in a predisposed host. The noxious luminal agent may be a single one, or multiple ones summing up to an individual threshold. […] Though a limited number of familial clusters of microscopic colitis have been reported, there is only minimal evidence of a genetic component within the etiology of microscopic colitis. […] Very strong evidence exists for an autoimmune basis to the development of both collagenous colitis and lymphocytic colitis. […] Luminal factors of whatever kind seem to play an important role in the pathogenesis of microscopic colitis. […] Basic science is still in its infancy, when it comes to studying microscopic colitis and possible causes, drivers, mechanisms, or even pathophysiological models.

• #17 Microscopic colitis: Common cause of unexplained nonbloody diarrhea

  https://www.wjgnet.com/2150-5330/full/v5/i1/48.htm

  Microscopic colitis (MC) is characterized by chronic, watery, secretory diarrhea, with a normal or near normal gross appearance of the colonic mucosa. […] The etiology of MC is most likely multifactorial with a mucosal inflammatory response to yet not specified noxious luminal agent occurring in a predisposed host. […] Technically, MC is an inflammatory bowel disease (IBD) and the disease shares a number of etiological aspects with the so-called classical inflammatory bowel diseases like Crohns disease and ulcerative colitis. […] Very strong evidence exists for an autoimmune basis to the development of both collagenous and lymphocytic colitis. […] The association of MC with autoimmune-based disorders such as celiac, thyroid disease and rheumatoid arthritis, as well as the female preponderance, supports the notion that both forms of MC have a strong association with autoimmune diseases and may well be an autoimmune disorder themselves.

• #18 Microscopic Colitis: Pathogenesis and Diagnosis

  https://pmc.ncbi.nlm.nih.gov/articles/PMC10342440/

  To date, the pathogenesis of microscopic colitis remains unknown and is likely complex and multifactorial. The possible mechanisms include intraluminal factors, such as abnormal microbiota, genetic predisposition, bile acids, and autoimmunity, which could trigger chronic inflammation. […] The role that genetics have in the pathogenesis of microscopic colitis is not completely understood. It has been proposed that microscopic colitis is the result of an abnormal immune response to luminal antigens in genetically predisposed individuals. […] The gut microbiome is another factor that may have implications in the pathogenesis of microscopic colitis. […] Autoimmunity is a possible pathophysiological mechanism in microscopic colitis. […] The association between bile acid malabsorption and microscopic colitis remains poorly understood and is complicated by the complex physiology and metabolism of bile acids in the intestinal tract. […] The pathogenesis of bile acid malabsorption in patients with microscopic colitis likely has several mechanisms.

• #19 Microscopic Colitis: Pathogenesis and Diagnosis

  https://www.mdpi.com/2077-0383/12/13/4442

  Microscopic colitis is an inflammatory bowel disease possibly caused by a chronic immune-mediated process. The pathogenesis of microscopic colitis remains unknown and is likely complex and multifactorial. The possible mechanisms include intraluminal factors, such as abnormal microbiota, genetic predisposition, bile acids, and autoimmunity, which could trigger chronic inflammation. To date, the pathogenesis of microscopic colitis remains unknown and is likely complex and multifactorial. The role that genetics have in the pathogenesis of microscopic colitis is not completely understood. It has been proposed that microscopic colitis is the result of an abnormal immune response to luminal antigens in genetically predisposed individuals. The gut microbiome is another factor that may have implications in the pathogenesis of microscopic colitis. Autoimmunity is a possible pathophysiological mechanism in microscopic colitis. The association between bile acid malabsorption and microscopic colitis remains poorly understood and is complicated by the complex physiology and metabolism of bile acids in the intestinal tract. The pathogenesis of bile acid malabsorption in patients with microscopic colitis likely has several mechanisms. In summary, these studies indicate that bile acids may have a primary or secondary effect in microscopic colitis.

• #20 Prevalence, Pathogenesis, Diagnosis, and Management of Microscopic Colitis

  https://www.gutnliver.org/journal/view.html?doi=10.5009/gnl17061

  A luminal component is supported as observation of a small number of patients who have undergone a diverting ileostomy demonstrate histologic improvement in their MC, which returns upon reconnection and resumption of the fecal stream. […] Exposure to a luminal antigen (medication, dietary, bile salts, bacteria) may cause an inflammatory cascade due to activation of CD8 T suppressor cells that may directly attack and damage the enterocyte. […] There is a proposed association between MC and celiac disease (CD), with an increased risk of 50- to 70-fold compared to the general population. […] CD is associated with the human leukocyte antigen (HLA) class II genes, particularly HLA DQ2 and HLA DQ8 alleles. […] The presence of HLA DQ2 types was also described in an additional study of 80 patients with MC (29 CC, 51 LC).

• #21 SciELO Brazil – Microscopic colitis: A literature review Microscopic colitis: A literature review

  https://www.scielo.br/j/ramb/a/Pg3NLNmt4FyPCHcRRnGhHBR/

  The pathophysiology of MC is still unknown, but it is believed that it is due to a multifactorial etiology, involving an exacerbated immune response to harmful luminal agents in the mucosa of these individuals. […] There is strong evidence of an autoimmune basis for CC and LC, both of which are associated with diseases such as celiac disease (12%), thyroid diseases (10.3%), Sjgrens syndrome (3.4%) and diabetes mellitus (1.7%). […] Various autoantibodies and phenotypes can be found along with MC, including the DR3 phenotype of human leukocyte antigen (HLA). However, no specific autoantibody has been identified as relevant in the diagnosis. […] Several luminal factors have an important role in the pathogenesis of MC. Many drugs are cited, such as aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs), proton pump inhibitors (PPIs), sertraline, ranitidine, simvastatin, carbamazepine, and more.

• #22 Microscopic colitis: Common cause of unexplained nonbloody diarrhea

  https://www.wjgnet.com/2150-5330/full/v5/i1/48.htm

  Microscopic colitis (MC) is characterized by chronic, watery, secretory diarrhea, with a normal or near normal gross appearance of the colonic mucosa. […] The etiology of MC is most likely multifactorial with a mucosal inflammatory response to yet not specified noxious luminal agent occurring in a predisposed host. […] Technically, MC is an inflammatory bowel disease (IBD) and the disease shares a number of etiological aspects with the so-called classical inflammatory bowel diseases like Crohns disease and ulcerative colitis. […] Very strong evidence exists for an autoimmune basis to the development of both collagenous and lymphocytic colitis. […] The association of MC with autoimmune-based disorders such as celiac, thyroid disease and rheumatoid arthritis, as well as the female preponderance, supports the notion that both forms of MC have a strong association with autoimmune diseases and may well be an autoimmune disorder themselves.

• #23 Microscopic (lymphocytic and collagenous) colitis: Clinical manifestations, diagnosis, and management – UpToDate

  https://www.uptodate.com/contents/microscopic-lymphocytic-and-collagenous-colitis-clinical-manifestations-diagnosis-and-management

  Microscopic colitis demonstrates a T helper type 1 mucosal cytokine response pattern with upregulated interferon gamma and interleukin-15, tumor necrosis factor, and nitric oxide synthase, a pattern similar to that in celiac disease. […] Whether these associations reflect an autoimmune pathogenesis of microscopic colitis is unclear.

• #24 Microscopic (lymphocytic and collagenous) colitis: Clinical manifestations, diagnosis, and management – UpToDate

  https://www.uptodate.com/contents/microscopic-lymphocytic-and-collagenous-colitis-clinical-manifestations-diagnosis-and-management/print

  Microscopic colitis has also been associated with several other diseases with autoimmune background (eg, autoimmune thyroiditis, type 1 diabetes mellitus, and nonerosive, oligoarticular arthritis). […] Whether these associations reflect an autoimmune pathogenesis of microscopic colitis is unclear. […] Microscopic colitis demonstrates a T helper type 1 mucosal cytokine response pattern with upregulated interferon gamma and interleukin-15, tumor necrosis factor, and nitric oxide synthase, a pattern similar to that in celiac disease.

• #25 Microscopic (lymphocytic and collagenous) colitis: Clinical manifestations, diagnosis, and management – UpToDate

  https://www.uptodate.com/contents/microscopic-lymphocytic-and-collagenous-colitis-clinical-manifestations-diagnosis-and-management

  Microscopic colitis demonstrates a T helper type 1 mucosal cytokine response pattern with upregulated interferon gamma and interleukin-15, tumor necrosis factor, and nitric oxide synthase, a pattern similar to that in celiac disease. […] Whether these associations reflect an autoimmune pathogenesis of microscopic colitis is unclear.

• #26 Microscopic colitis: Etiopathology, diagnosis, and rational management | eLife

  https://elifesciences.org/articles/79397

  The pathogenesis of microscopic colitis is still poorly elucidated, but it is likely a result of dysbalanced immune response involving epithelial dysfunction, collagen metabolism, secretory diarrhea, and microbiota, combined with the risk factors mentioned above in genetically predisposed individuals. […] The bacterial flora in the colon is an important luminal factor that directly or indirectly interacts with colonic epithelium, and thus, its alteration might contribute to the pathogenesis of microscopic colitis. […] Although microscopic colitis is considered as a noninfectious colitis, recent advances in sequencing analysis have demonstrated an alteration of intestinal bacterial composition, referred to as dysbiosis. […] A recent sequencing study showed microbiota from microscopic colitis to be significantly less diverse and compositionally distinct from healthy controls due to depletion of members of Clostridiales; enriched for Prevotella and more likely dominated by this genus.

• #27 Microscopic colitis—microbiome, barrier function and associated diseases

  https://atm.amegroups.org/article/view/14674/html

  Microscopic colitis (MC) is a chronic inflammatory bowel disease (IBD) with little in terms of endoscopic abnormalities and is frequently associated with other autoimmune diseases. […] The pathogenesis of MC is complex, multifactorial and poorly understood. Current concepts revolve around innate immunity or microbiome alterations as well as gut barrier dysfunction, all of which lead to the development of subtle inflammatory lesions in gut mucosa. […] The results of numerous basic and clinical studies involving molecular techniques as well as advanced endoscopic imaging revealed the important role of both intrinsic (e.g., hormonal) as well as extrinsic (e.g., NSAIDs and PPIs) factors in the modulation of gastrointestinal microbiome and MC pathogenesis. […] The pathophysiological cause of MC is unknown, but recent hypotheses revolve around mucosal inflammation, microbiome and gut barrier alterations. Several extrinsic (environmental) as well as intrinsic (endocrine) factors might play a role in the pathogenesis of the disease.

• #28 Microscopic colitis: Etiopathology, diagnosis, and rational management | eLife

  https://elifesciences.org/articles/79397

  The pathogenesis of microscopic colitis is still poorly elucidated, but it is likely a result of dysbalanced immune response involving epithelial dysfunction, collagen metabolism, secretory diarrhea, and microbiota, combined with the risk factors mentioned above in genetically predisposed individuals. […] The bacterial flora in the colon is an important luminal factor that directly or indirectly interacts with colonic epithelium, and thus, its alteration might contribute to the pathogenesis of microscopic colitis. […] Although microscopic colitis is considered as a noninfectious colitis, recent advances in sequencing analysis have demonstrated an alteration of intestinal bacterial composition, referred to as dysbiosis. […] A recent sequencing study showed microbiota from microscopic colitis to be significantly less diverse and compositionally distinct from healthy controls due to depletion of members of Clostridiales; enriched for Prevotella and more likely dominated by this genus.

• #29 Microscopic colitis: Etiopathology, diagnosis, and rational management | eLife

  https://elifesciences.org/articles/79397

  The pathogenesis of microscopic colitis is still poorly elucidated, but it is likely a result of dysbalanced immune response involving epithelial dysfunction, collagen metabolism, secretory diarrhea, and microbiota, combined with the risk factors mentioned above in genetically predisposed individuals. […] The bacterial flora in the colon is an important luminal factor that directly or indirectly interacts with colonic epithelium, and thus, its alteration might contribute to the pathogenesis of microscopic colitis. […] Although microscopic colitis is considered as a noninfectious colitis, recent advances in sequencing analysis have demonstrated an alteration of intestinal bacterial composition, referred to as dysbiosis. […] A recent sequencing study showed microbiota from microscopic colitis to be significantly less diverse and compositionally distinct from healthy controls due to depletion of members of Clostridiales; enriched for Prevotella and more likely dominated by this genus.

• #30 Microscopic colitis: Etiopathology, diagnosis, and rational management | eLife

  https://elifesciences.org/articles/79397

  The de-enrichment of Akkermansia muciniphila was additionally observed in a study using PCR. […] More recently, a team of researchers found a higher long-term risk of developing microscopic colitis in patients whose stool carried Campylobacter concisus. […] Campylobacter concisus is associated with epithelial sodium channel dysfunction and claudin-8-dependent barrier dysfunction, suggesting their involvement in the pathogenesis of microscopic colitis. […] Notably, the intake of PPI and smoking influences bacterial flora, especially the former may especially increase the abundance of oral microbes, such as C. concisus, suggesting that dysbiosis may be the mechanism by which these factors cause microscopic colitis. […] A genetic component is of importance as well, and a recent genetic immunochip study reported an association between the human leukocyte antigen (HLA) ancestral 8.1 haplotype and well-established collagenous colitis but not with lymphocytic colitis.

• #31 Microscopic colitis: Etiopathology, diagnosis, and rational management | eLife

  https://elifesciences.org/articles/79397

  The de-enrichment of Akkermansia muciniphila was additionally observed in a study using PCR. […] More recently, a team of researchers found a higher long-term risk of developing microscopic colitis in patients whose stool carried Campylobacter concisus. […] Campylobacter concisus is associated with epithelial sodium channel dysfunction and claudin-8-dependent barrier dysfunction, suggesting their involvement in the pathogenesis of microscopic colitis. […] Notably, the intake of PPI and smoking influences bacterial flora, especially the former may especially increase the abundance of oral microbes, such as C. concisus, suggesting that dysbiosis may be the mechanism by which these factors cause microscopic colitis. […] A genetic component is of importance as well, and a recent genetic immunochip study reported an association between the human leukocyte antigen (HLA) ancestral 8.1 haplotype and well-established collagenous colitis but not with lymphocytic colitis.

• #32 Microscopic colitis: Etiopathology, diagnosis, and rational management | eLife

  https://elifesciences.org/articles/79397

  The de-enrichment of Akkermansia muciniphila was additionally observed in a study using PCR. […] More recently, a team of researchers found a higher long-term risk of developing microscopic colitis in patients whose stool carried Campylobacter concisus. […] Campylobacter concisus is associated with epithelial sodium channel dysfunction and claudin-8-dependent barrier dysfunction, suggesting their involvement in the pathogenesis of microscopic colitis. […] Notably, the intake of PPI and smoking influences bacterial flora, especially the former may especially increase the abundance of oral microbes, such as C. concisus, suggesting that dysbiosis may be the mechanism by which these factors cause microscopic colitis. […] A genetic component is of importance as well, and a recent genetic immunochip study reported an association between the human leukocyte antigen (HLA) ancestral 8.1 haplotype and well-established collagenous colitis but not with lymphocytic colitis.

• #33 Microscopic colitis: Etiopathology, diagnosis, and rational management | eLife

  https://elifesciences.org/articles/79397

  The de-enrichment of Akkermansia muciniphila was additionally observed in a study using PCR. […] More recently, a team of researchers found a higher long-term risk of developing microscopic colitis in patients whose stool carried Campylobacter concisus. […] Campylobacter concisus is associated with epithelial sodium channel dysfunction and claudin-8-dependent barrier dysfunction, suggesting their involvement in the pathogenesis of microscopic colitis. […] Notably, the intake of PPI and smoking influences bacterial flora, especially the former may especially increase the abundance of oral microbes, such as C. concisus, suggesting that dysbiosis may be the mechanism by which these factors cause microscopic colitis. […] A genetic component is of importance as well, and a recent genetic immunochip study reported an association between the human leukocyte antigen (HLA) ancestral 8.1 haplotype and well-established collagenous colitis but not with lymphocytic colitis.

• #34 Microscopic Colitis: New PPI Data – Gastroenterology Advisor

  https://www.gastroenterologyadvisor.com/features/microscopic-colitis-new-ppi-data/

  The exact pathophysiology of microscopic colitis is not completely understood, though PPIs and NSAIDs are 2 medications commonly implicated for triggering the inflammatory process. […] The exact pathophysiology is not completely understood and may be multifactorial, with possible contributions by autoimmunity, hormone levels, dysregulation of the colonic mucosa and immune system (including the gut microbiome), and a genetic predisposition. […] It has been postulated that PPIs may lead to MC via reduction of gastric acidity, which causes changes in the gut microbiome and electrolyte concentration within the colonic lumen. These changes could induce intraepithelial lymphocytosis and subsequently inflammation and resulting diarrhea. […] NSAIDs may predispose patients to developing MC based on their pharmacologic mechanism of inhibiting cyclooxygenase, leading to disruptions in the colonic mucosal barriers and increased translocation of potential bacteria and toxins.

• #35 Microscopic colitis—microbiome, barrier function and associated diseases

  https://atm.amegroups.org/article/view/14674/html

  Multiple studies have investigated different mechanisms that might be involved in the development of mucosal inflammation in MC. […] The gut barrier is a complex, multicomponent system in which different cell types in and around the gut wall work together to prevent unwanted translocation of components from the lumen of the gut into the body. […] Increased intestinal permeability is associated with a variety of gastrointestinal (GI) disorders, including IBD, irritable bowel syndrome and celiac disease. […] Budesonide seems to affect the mucosal barrier function, it has anti-proliferative effects on the epithelial cells, which might impair wound healing. […] The hypothesis that gut microbiota play role in the pathogenesis of MC is interesting, however poorly studied yet. […] Overall, these are all small studies which might give a clue about a possible role of the microbiota in MC, but much larger studies are necessary to unravel the role of the gut microbiota in MC.

• #36 Microscopic colitis—microbiome, barrier function and associated diseases

  https://atm.amegroups.org/article/view/14674/18553

  The gut barrier is a complex, multicomponent system in which different cell types in and around the gut wall work together to prevent unwanted translocation of components from the lumen of the gut into the body. […] Mucosal barrier dysfunction has also been described in IBD and MC patients. […] Budesonide seems to affect the mucosal barrier function, it has anti-proliferative effects on the epithelial cells, which might impair wound healing. […] The hypothesis that gut microbiota play role in the pathogenesis of MC is interesting, however poorly studied yet. […] Overall, these are all small studies which might give a clue about a possible role of the microbiota in MC, but much larger studies are necessary to unravel the role of the gut microbiota in MC. […] The intestinal barrier function is impaired in MC patients, and this is not restored during budesonide use. This might be a cause of the high relapse rate seen for this disease.

• #37 Microscopic Colitis: Epidemiology, Pathophysiology, Diagnosis and Current Management—An Update 2013

  https://pmc.ncbi.nlm.nih.gov/articles/PMC3654232/

  Using molecular techniques it was reported that in patients with microscopic colitis increased IFN-, TNF-, and IL-1 levels suggest a Th1 cytokine profile being involved in the inflammatory process. […] Environmental factors may play a crucial role in the etiology of microscopic colitis, though other than cigarette smoking presently no other such factor is confirmed. […] In addition to the inflammatory component in the pathophysiology of microscopic colitis, there may be an additional neuronal component to pathophysiology.

• #38 SciELO Brazil – Microscopic colitis: A literature review Microscopic colitis: A literature review

  https://www.scielo.br/j/ramb/a/Pg3NLNmt4FyPCHcRRnGhHBR/

  Malabsorption of bile acids was found in up to 60% of patients with LC and 44% of patients with CC, supporting the idea that this may be the cause of MC. […] Increases were also reported in interferon gamma (IFN-), tumor necrosis factor alpha (TNF-), interleukin 1 beta (IL-1), and a profile of Th1 cytokines, which are suggested to be involved in the inflammatory process. […] As for environmental factors, the major etiologic role is played by cigarettes. Smoking is more prevalent among patients with MC, and studies indicate an association with lung cancer. It has also been demonstrated that MC involvement in individuals that smoke occurs around 10 years earlier, increasing the relevance of this habit.

• #39 Microscopic Colitis: A Review of Collagenous and Lymphocytic Colitis – Gastroenterology & Hepatology

  https://www.gastroenterologyandhepatology.net/archives/november-2017/microscopic-colitis-a-review-of-collagenous-and-lymphocytic-colitis/

  Histology before and after ileostomy reversal found increased transcellular and tight junction permeability, proposing that mucosal barrier dysfunction has a role in CC. […] Furthermore, downregulation of the tight junction proteins claudin-4, -5, and -8, and their redistribution off the tight junction, triggered by tumor necrosis factor-α (TNF-α) and interferon-γ, contribute to diarrhea in LC. […] Medications associated with MC include nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin; selective serotonin reuptake inhibitors; proton pump inhibitors (PPIs); and drugs with various other mechanisms of action, including statins, beta blockers, angiotensin-converting enzyme inhibitors, and angiotensin receptor blockers. […] MC does not progress in a dose-dependent manner, and symptoms may be reported days to months after drug initiation, with a median time of 4 days to symptom onset. […] In summary, there is evidence to suggest that certain drugs may precipitate the onset of MC, and there should be consideration to stop these drugs to reduce the risk of relapse.

• #40 Microscopic Colitis: A Review of Collagenous and Lymphocytic Colitis – Gastroenterology & Hepatology

  https://www.gastroenterologyandhepatology.net/archives/november-2017/microscopic-colitis-a-review-of-collagenous-and-lymphocytic-colitis/

  Histology before and after ileostomy reversal found increased transcellular and tight junction permeability, proposing that mucosal barrier dysfunction has a role in CC. […] Furthermore, downregulation of the tight junction proteins claudin-4, -5, and -8, and their redistribution off the tight junction, triggered by tumor necrosis factor-α (TNF-α) and interferon-γ, contribute to diarrhea in LC. […] Medications associated with MC include nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin; selective serotonin reuptake inhibitors; proton pump inhibitors (PPIs); and drugs with various other mechanisms of action, including statins, beta blockers, angiotensin-converting enzyme inhibitors, and angiotensin receptor blockers. […] MC does not progress in a dose-dependent manner, and symptoms may be reported days to months after drug initiation, with a median time of 4 days to symptom onset. […] In summary, there is evidence to suggest that certain drugs may precipitate the onset of MC, and there should be consideration to stop these drugs to reduce the risk of relapse.

• #41

  https://www.xiahepublishing.com/2994-8754/JTG-2024-00025

  The prominent subepithelial collagen band in collagenous colitis has generated interest in aberrant collagen metabolism as a cause of the disease. Some research has demonstrated increased expression of the TGF-beta1 gene, a growth factor that can cause collagen accumulation in tissue, in patients with collagenous colitis. Another theory for the pathogenesis of microscopic colitis is that it may be medication-induced. A large population-based study found a significantly increased risk for the development of microscopic colitis in patients taking NSAIDs and PPIs compared to controls. The diarrhea in microscopic colitis is thought to arise from mucosal inflammation, supporting the idea that an intraluminal antigen plays a role in the development of symptoms. This theory is further supported by the finding that the severity of diarrhea correlates with the degree of inflammation within the lamina propria, not with the degree of subepithelial collagen band thickening.

• #42 Microscopic Colitis: An Underestimated Disease of Growing Importance

  https://www.mdpi.com/2077-0383/13/19/5683

  The aim of this paper is to raise awareness of MC as a clinically significant condition and to highlight its under-recognition, risk factors, diagnosis, management, and complications. […] The aetiology of the disease remains unclear. The aetiological factors include autoimmune diseases (such as ankylosing spondylitis (AS), psoriasis, Hashimoto’s disease, Graves–Basedow disease, and type 1 diabetes), as well as medications used (such as NSAIDs (Non-Steroidal Anti-Inflammatory Drugs), PPIs (Proton Pump Inhibitors), SSRIs (Selective Serotonin Reuptake Inhibitors), and ICPIs (immune check-point inhibitors)). […] The pathologies are considered subtypes of one disease due to their similar clinical manifestations, aetiology, pathogenesis, and therapeutic approach. […] The findings of Bjurström et al. suggest that NSAID use in individuals with MC may potentially contribute to relapse and the necessity for an additional cycle of budesonide treatment.

• #43 Microscopic Colitis: New PPI Data – Gastroenterology Advisor

  https://www.gastroenterologyadvisor.com/features/microscopic-colitis-new-ppi-data/

  The exact pathophysiology of microscopic colitis is not completely understood, though PPIs and NSAIDs are 2 medications commonly implicated for triggering the inflammatory process. […] The exact pathophysiology is not completely understood and may be multifactorial, with possible contributions by autoimmunity, hormone levels, dysregulation of the colonic mucosa and immune system (including the gut microbiome), and a genetic predisposition. […] It has been postulated that PPIs may lead to MC via reduction of gastric acidity, which causes changes in the gut microbiome and electrolyte concentration within the colonic lumen. These changes could induce intraepithelial lymphocytosis and subsequently inflammation and resulting diarrhea. […] NSAIDs may predispose patients to developing MC based on their pharmacologic mechanism of inhibiting cyclooxygenase, leading to disruptions in the colonic mucosal barriers and increased translocation of potential bacteria and toxins.

• #44 Diagnosis and Management of Microscopic Colitis: A Review of the Literature – Practical Gastro

  https://practicalgastro.com/2014/02/13/diagnosis-and-management-of-microscopic-colitis-a-review-of-the-literature/

  The etiology is multifactorial and the exact mechanism remains unknown. However, it is believed that a dysregulated immune response to a luminal agent leads to reduced sodium and chloride absorption as well as active chloride secretion. […] One study showed that the thick collagen band found in collagenous colitis may act as a diffusion barrier and down-regulate tight junction molecules. […] Medications that have been implicated in causing microscopic colitis include H2 blockers, PPI, SSRIs, carbamazepine, simvastatin, and ticlopidine. […] Lansoprazole, for example, a potent and commonly used PPI has been extensively studied for its association with microscopic colitis. […] A case study of 850 patients who were switched from omeprazole to lansoprazole showed direct correlation of lansoprazole with intermittent diarrhea characterized as lymphocytic and collagenous colitis on histology. When lansoprazole was discontinued, follow-up biopsies revealed resolution with normalization of colonic histology.

• #45 Prevalence, Pathogenesis, Diagnosis, and Management of Microscopic Colitis

  https://www.gutnliver.org/journal/view.html?volume=12&number=3&spage=227

  Microscopic colitis (MC), which is comprised of lymphocytic colitis and collagenous colitis, is a clinicopathological diagnosis that is commonly encountered in clinical practice during the evaluation and management of chronic diarrhea. […] The mechanism of diarrhea in the cause of MC remains largely unknown, partly due to lack of animal models. […] Sodium chloride absorption in biopsies of patients with CC has been further studied at the molecular level. Ultimately, researchers found that there was a decrease in both Na+ and Cl absorption, epithelial resistance, occludin and claudin-4 expression, regulation of tight junction molecules, resulting in a dysfunction of the collagen barrier and ultimately, leading to a secretory diarrhea. […] Another mechanism of diarrhea involves bile acid malabsorption. Bile acid sequestrants such as cholestyramine have been used with varying success in some patients with MC.

• #46 Prevalence, Pathogenesis, Diagnosis, and Management of Microscopic Colitis

  https://www.gutnliver.org/journal/view.html?doi=10.5009/gnl17061

  Microscopic colitis (MC), which is comprised of lymphocytic colitis and collagenous colitis, is a clinicopathological diagnosis that is commonly encountered in clinical practice during the evaluation and management of chronic diarrhea. […] The mechanism of diarrhea in the cause of MC remains largely unknown, partly due to lack of animal models. […] Sodium chloride absorption in biopsies of patients with CC has been further studied at the molecular level. Ultimately, researchers found that there was a decrease in both Na+ and Cl absorption, epithelial resistance, occludin and claudin-4 expression, regulation of tight junction molecules, resulting in a dysfunction of the collagen barrier and ultimately, leading to a secretory diarrhea. […] Another mechanism of diarrhea involves bile acid malabsorption.

• #47

  https://www.asge.org/home/resources/key-resources/blog/view/practical-solutions/2023/09/27/case-9–microscopic-colitis

  Microscopic colitis is a chronic disease of the colon, characterized by chronic, watery, non-bloody diarrhea. Microscopic colitis is subdivided into collagenous colitis and lymphocytic colitis. […] The pathogenesis of microscopic colitis is unknown; it is likely multifactorial, involving mucosal immune response to luminal factors in a genetically predisposed individual. Diarrhea in microscopic colitis is likely secondary to mucosal inflammation and bile acid malabsorption. […] Histologically, the inflammatory cell response is similar for lymphocytic colitis and collagenous colitis, consisting of mononuclear cells, with few neutrophils and eosinophils in the lamina propria.

• #48 Prevalence, Pathogenesis, Diagnosis, and Management of Microscopic Colitis

  https://www.gutnliver.org/journal/view.html?volume=12&number=3&spage=227

  Microscopic colitis (MC), which is comprised of lymphocytic colitis and collagenous colitis, is a clinicopathological diagnosis that is commonly encountered in clinical practice during the evaluation and management of chronic diarrhea. […] The mechanism of diarrhea in the cause of MC remains largely unknown, partly due to lack of animal models. […] Sodium chloride absorption in biopsies of patients with CC has been further studied at the molecular level. Ultimately, researchers found that there was a decrease in both Na+ and Cl absorption, epithelial resistance, occludin and claudin-4 expression, regulation of tight junction molecules, resulting in a dysfunction of the collagen barrier and ultimately, leading to a secretory diarrhea. […] Another mechanism of diarrhea involves bile acid malabsorption. Bile acid sequestrants such as cholestyramine have been used with varying success in some patients with MC.

• #49 Prevalence, Pathogenesis, Diagnosis, and Management of Microscopic Colitis

  https://www.gutnliver.org/journal/view.html?doi=10.5009/gnl17061

  Microscopic colitis (MC), which is comprised of lymphocytic colitis and collagenous colitis, is a clinicopathological diagnosis that is commonly encountered in clinical practice during the evaluation and management of chronic diarrhea. […] The mechanism of diarrhea in the cause of MC remains largely unknown, partly due to lack of animal models. […] Sodium chloride absorption in biopsies of patients with CC has been further studied at the molecular level. Ultimately, researchers found that there was a decrease in both Na+ and Cl absorption, epithelial resistance, occludin and claudin-4 expression, regulation of tight junction molecules, resulting in a dysfunction of the collagen barrier and ultimately, leading to a secretory diarrhea. […] Another mechanism of diarrhea involves bile acid malabsorption.

• #50 SciELO Brazil – Microscopic colitis: A literature review Microscopic colitis: A literature review

  https://www.scielo.br/j/ramb/a/Pg3NLNmt4FyPCHcRRnGhHBR/

  Malabsorption of bile acids was found in up to 60% of patients with LC and 44% of patients with CC, supporting the idea that this may be the cause of MC. […] Increases were also reported in interferon gamma (IFN-), tumor necrosis factor alpha (TNF-), interleukin 1 beta (IL-1), and a profile of Th1 cytokines, which are suggested to be involved in the inflammatory process. […] As for environmental factors, the major etiologic role is played by cigarettes. Smoking is more prevalent among patients with MC, and studies indicate an association with lung cancer. It has also been demonstrated that MC involvement in individuals that smoke occurs around 10 years earlier, increasing the relevance of this habit.

• #51 Microscopic Colitis: Pathogenesis and Diagnosis

  https://pmc.ncbi.nlm.nih.gov/articles/PMC10342440/

  To date, the pathogenesis of microscopic colitis remains unknown and is likely complex and multifactorial. The possible mechanisms include intraluminal factors, such as abnormal microbiota, genetic predisposition, bile acids, and autoimmunity, which could trigger chronic inflammation. […] The role that genetics have in the pathogenesis of microscopic colitis is not completely understood. It has been proposed that microscopic colitis is the result of an abnormal immune response to luminal antigens in genetically predisposed individuals. […] The gut microbiome is another factor that may have implications in the pathogenesis of microscopic colitis. […] Autoimmunity is a possible pathophysiological mechanism in microscopic colitis. […] The association between bile acid malabsorption and microscopic colitis remains poorly understood and is complicated by the complex physiology and metabolism of bile acids in the intestinal tract. […] The pathogenesis of bile acid malabsorption in patients with microscopic colitis likely has several mechanisms.

• #52 Microscopic Colitis: Pathogenesis and Diagnosis

  https://www.mdpi.com/2077-0383/12/13/4442

  Microscopic colitis is an inflammatory bowel disease possibly caused by a chronic immune-mediated process. The pathogenesis of microscopic colitis remains unknown and is likely complex and multifactorial. The possible mechanisms include intraluminal factors, such as abnormal microbiota, genetic predisposition, bile acids, and autoimmunity, which could trigger chronic inflammation. To date, the pathogenesis of microscopic colitis remains unknown and is likely complex and multifactorial. The role that genetics have in the pathogenesis of microscopic colitis is not completely understood. It has been proposed that microscopic colitis is the result of an abnormal immune response to luminal antigens in genetically predisposed individuals. The gut microbiome is another factor that may have implications in the pathogenesis of microscopic colitis. Autoimmunity is a possible pathophysiological mechanism in microscopic colitis. The association between bile acid malabsorption and microscopic colitis remains poorly understood and is complicated by the complex physiology and metabolism of bile acids in the intestinal tract. The pathogenesis of bile acid malabsorption in patients with microscopic colitis likely has several mechanisms. In summary, these studies indicate that bile acids may have a primary or secondary effect in microscopic colitis.

• #53 Microscopic Colitis: An Underestimated Disease of Growing Importance

  https://www.mdpi.com/2077-0383/13/19/5683

  It is hypothesized that PPIs may precipitate the onset of the disease due to an increase in gastric pH and subsequent intestinal dysbiosis and electrolyte imbalance. […] It is hypothesized that the inhibition of PD-1, PD-L1, and CTLA-4 may result in the activation of Th1 and Th17 lymphocytes, leading to an increased production of pro-inflammatory cytokines. […] The underlying mechanism of autoimmune disease coexistence in MC is likely related to chronic inflammation confined to the colon. […] It seems reasonable to posit that bile acids that have not been absorbed may induce intestinal dysbiosis. […] The Farnesoid X Receptor (FXR) is a key nuclear receptor for bile acids, primarily expressed in the proximal colon as well as the liver. […] These conditions may share a similar molecular basis involving the Farnesoid X Receptor (FXR), Takeda G-Protein-Coupled Receptor 5 (TGR5), gut dysbiosis, and the Apical Sodium-Dependent Bile Acid Transporter (ASBT).

• #54 Microscopic Colitis: An Underestimated Disease of Growing Importance

  https://www.mdpi.com/2077-0383/13/19/5683

  It is hypothesized that PPIs may precipitate the onset of the disease due to an increase in gastric pH and subsequent intestinal dysbiosis and electrolyte imbalance. […] It is hypothesized that the inhibition of PD-1, PD-L1, and CTLA-4 may result in the activation of Th1 and Th17 lymphocytes, leading to an increased production of pro-inflammatory cytokines. […] The underlying mechanism of autoimmune disease coexistence in MC is likely related to chronic inflammation confined to the colon. […] It seems reasonable to posit that bile acids that have not been absorbed may induce intestinal dysbiosis. […] The Farnesoid X Receptor (FXR) is a key nuclear receptor for bile acids, primarily expressed in the proximal colon as well as the liver. […] These conditions may share a similar molecular basis involving the Farnesoid X Receptor (FXR), Takeda G-Protein-Coupled Receptor 5 (TGR5), gut dysbiosis, and the Apical Sodium-Dependent Bile Acid Transporter (ASBT).

• #55 Microscopic Colitis: An Underestimated Disease of Growing Importance

  https://www.mdpi.com/2077-0383/13/19/5683

  It is hypothesized that PPIs may precipitate the onset of the disease due to an increase in gastric pH and subsequent intestinal dysbiosis and electrolyte imbalance. […] It is hypothesized that the inhibition of PD-1, PD-L1, and CTLA-4 may result in the activation of Th1 and Th17 lymphocytes, leading to an increased production of pro-inflammatory cytokines. […] The underlying mechanism of autoimmune disease coexistence in MC is likely related to chronic inflammation confined to the colon. […] It seems reasonable to posit that bile acids that have not been absorbed may induce intestinal dysbiosis. […] The Farnesoid X Receptor (FXR) is a key nuclear receptor for bile acids, primarily expressed in the proximal colon as well as the liver. […] These conditions may share a similar molecular basis involving the Farnesoid X Receptor (FXR), Takeda G-Protein-Coupled Receptor 5 (TGR5), gut dysbiosis, and the Apical Sodium-Dependent Bile Acid Transporter (ASBT).

• #56 Microscopic Colitis: Pathogenesis and Diagnosis

  https://pmc.ncbi.nlm.nih.gov/articles/PMC10342440/

  To date, the pathogenesis of microscopic colitis remains unknown and is likely complex and multifactorial. The possible mechanisms include intraluminal factors, such as abnormal microbiota, genetic predisposition, bile acids, and autoimmunity, which could trigger chronic inflammation. […] The role that genetics have in the pathogenesis of microscopic colitis is not completely understood. It has been proposed that microscopic colitis is the result of an abnormal immune response to luminal antigens in genetically predisposed individuals. […] The gut microbiome is another factor that may have implications in the pathogenesis of microscopic colitis. […] Autoimmunity is a possible pathophysiological mechanism in microscopic colitis. […] The association between bile acid malabsorption and microscopic colitis remains poorly understood and is complicated by the complex physiology and metabolism of bile acids in the intestinal tract. […] The pathogenesis of bile acid malabsorption in patients with microscopic colitis likely has several mechanisms.

• #57 Microscopic Colitis: Pathogenesis and Diagnosis

  https://www.mdpi.com/2077-0383/12/13/4442

  Microscopic colitis is an inflammatory bowel disease possibly caused by a chronic immune-mediated process. The pathogenesis of microscopic colitis remains unknown and is likely complex and multifactorial. The possible mechanisms include intraluminal factors, such as abnormal microbiota, genetic predisposition, bile acids, and autoimmunity, which could trigger chronic inflammation. To date, the pathogenesis of microscopic colitis remains unknown and is likely complex and multifactorial. The role that genetics have in the pathogenesis of microscopic colitis is not completely understood. It has been proposed that microscopic colitis is the result of an abnormal immune response to luminal antigens in genetically predisposed individuals. The gut microbiome is another factor that may have implications in the pathogenesis of microscopic colitis. Autoimmunity is a possible pathophysiological mechanism in microscopic colitis. The association between bile acid malabsorption and microscopic colitis remains poorly understood and is complicated by the complex physiology and metabolism of bile acids in the intestinal tract. The pathogenesis of bile acid malabsorption in patients with microscopic colitis likely has several mechanisms. In summary, these studies indicate that bile acids may have a primary or secondary effect in microscopic colitis.

• #58 Microscopic Colitis: Pathogenesis and Diagnosis

  https://www.mdpi.com/2077-0383/12/13/4442

  Microscopic colitis is an inflammatory bowel disease possibly caused by a chronic immune-mediated process. The pathogenesis of microscopic colitis remains unknown and is likely complex and multifactorial. The possible mechanisms include intraluminal factors, such as abnormal microbiota, genetic predisposition, bile acids, and autoimmunity, which could trigger chronic inflammation. To date, the pathogenesis of microscopic colitis remains unknown and is likely complex and multifactorial. The role that genetics have in the pathogenesis of microscopic colitis is not completely understood. It has been proposed that microscopic colitis is the result of an abnormal immune response to luminal antigens in genetically predisposed individuals. The gut microbiome is another factor that may have implications in the pathogenesis of microscopic colitis. Autoimmunity is a possible pathophysiological mechanism in microscopic colitis. The association between bile acid malabsorption and microscopic colitis remains poorly understood and is complicated by the complex physiology and metabolism of bile acids in the intestinal tract. The pathogenesis of bile acid malabsorption in patients with microscopic colitis likely has several mechanisms. In summary, these studies indicate that bile acids may have a primary or secondary effect in microscopic colitis.

• #59 Microscopic colitis—microbiome, barrier function and associated diseases

  https://atm.amegroups.org/article/view/14674/html

  Multiple studies have investigated different mechanisms that might be involved in the development of mucosal inflammation in MC. […] The gut barrier is a complex, multicomponent system in which different cell types in and around the gut wall work together to prevent unwanted translocation of components from the lumen of the gut into the body. […] Increased intestinal permeability is associated with a variety of gastrointestinal (GI) disorders, including IBD, irritable bowel syndrome and celiac disease. […] Budesonide seems to affect the mucosal barrier function, it has anti-proliferative effects on the epithelial cells, which might impair wound healing. […] The hypothesis that gut microbiota play role in the pathogenesis of MC is interesting, however poorly studied yet. […] Overall, these are all small studies which might give a clue about a possible role of the microbiota in MC, but much larger studies are necessary to unravel the role of the gut microbiota in MC.

• #60 Microscopic colitis—microbiome, barrier function and associated diseases

  https://atm.amegroups.org/article/view/14674/18553

  The gut barrier is a complex, multicomponent system in which different cell types in and around the gut wall work together to prevent unwanted translocation of components from the lumen of the gut into the body. […] Mucosal barrier dysfunction has also been described in IBD and MC patients. […] Budesonide seems to affect the mucosal barrier function, it has anti-proliferative effects on the epithelial cells, which might impair wound healing. […] The hypothesis that gut microbiota play role in the pathogenesis of MC is interesting, however poorly studied yet. […] Overall, these are all small studies which might give a clue about a possible role of the microbiota in MC, but much larger studies are necessary to unravel the role of the gut microbiota in MC. […] The intestinal barrier function is impaired in MC patients, and this is not restored during budesonide use. This might be a cause of the high relapse rate seen for this disease.

• #61 Microscopic colitis—microbiome, barrier function and associated diseases

  https://atm.amegroups.org/article/view/14674/html

  Multiple studies have investigated different mechanisms that might be involved in the development of mucosal inflammation in MC. […] The gut barrier is a complex, multicomponent system in which different cell types in and around the gut wall work together to prevent unwanted translocation of components from the lumen of the gut into the body. […] Increased intestinal permeability is associated with a variety of gastrointestinal (GI) disorders, including IBD, irritable bowel syndrome and celiac disease. […] Budesonide seems to affect the mucosal barrier function, it has anti-proliferative effects on the epithelial cells, which might impair wound healing. […] The hypothesis that gut microbiota play role in the pathogenesis of MC is interesting, however poorly studied yet. […] Overall, these are all small studies which might give a clue about a possible role of the microbiota in MC, but much larger studies are necessary to unravel the role of the gut microbiota in MC.

• #62 Microscopic colitis—microbiome, barrier function and associated diseases

  https://atm.amegroups.org/article/view/14674/18553

  The gut barrier is a complex, multicomponent system in which different cell types in and around the gut wall work together to prevent unwanted translocation of components from the lumen of the gut into the body. […] Mucosal barrier dysfunction has also been described in IBD and MC patients. […] Budesonide seems to affect the mucosal barrier function, it has anti-proliferative effects on the epithelial cells, which might impair wound healing. […] The hypothesis that gut microbiota play role in the pathogenesis of MC is interesting, however poorly studied yet. […] Overall, these are all small studies which might give a clue about a possible role of the microbiota in MC, but much larger studies are necessary to unravel the role of the gut microbiota in MC. […] The intestinal barrier function is impaired in MC patients, and this is not restored during budesonide use. This might be a cause of the high relapse rate seen for this disease.

• #63 Microscopic colitis—microbiome, barrier function and associated diseases

  https://atm.amegroups.org/article/view/14674/html

  Multiple studies have investigated different mechanisms that might be involved in the development of mucosal inflammation in MC. […] The gut barrier is a complex, multicomponent system in which different cell types in and around the gut wall work together to prevent unwanted translocation of components from the lumen of the gut into the body. […] Increased intestinal permeability is associated with a variety of gastrointestinal (GI) disorders, including IBD, irritable bowel syndrome and celiac disease. […] Budesonide seems to affect the mucosal barrier function, it has anti-proliferative effects on the epithelial cells, which might impair wound healing. […] The hypothesis that gut microbiota play role in the pathogenesis of MC is interesting, however poorly studied yet. […] Overall, these are all small studies which might give a clue about a possible role of the microbiota in MC, but much larger studies are necessary to unravel the role of the gut microbiota in MC.

• #64 Microscopic colitis—microbiome, barrier function and associated diseases

  https://atm.amegroups.org/article/view/14674/18553

  The gut barrier is a complex, multicomponent system in which different cell types in and around the gut wall work together to prevent unwanted translocation of components from the lumen of the gut into the body. […] Mucosal barrier dysfunction has also been described in IBD and MC patients. […] Budesonide seems to affect the mucosal barrier function, it has anti-proliferative effects on the epithelial cells, which might impair wound healing. […] The hypothesis that gut microbiota play role in the pathogenesis of MC is interesting, however poorly studied yet. […] Overall, these are all small studies which might give a clue about a possible role of the microbiota in MC, but much larger studies are necessary to unravel the role of the gut microbiota in MC. […] The intestinal barrier function is impaired in MC patients, and this is not restored during budesonide use. This might be a cause of the high relapse rate seen for this disease.

• #65 Microscopic colitis—microbiome, barrier function and associated diseases

  https://atm.amegroups.org/article/view/14674/html

  The intestinal barrier function is impaired in MC patients, and this is not restored during budesonide use. This might be a cause of the high relapse rate seen for this disease. […] It can be speculated that the use of probiotics or other agents capable of modulation of gut microbiota and intestinal barrier might benefit MC patients, but the current evidence is very limited and further clinical studies are necessary to see if probiotics or other new pharmacologic molecules can play a role in the treatment of prevention of relapse of the disease.

• #66 Microscopic colitis—microbiome, barrier function and associated diseases

  https://atm.amegroups.org/article/view/14674/18553

  The gut barrier is a complex, multicomponent system in which different cell types in and around the gut wall work together to prevent unwanted translocation of components from the lumen of the gut into the body. […] Mucosal barrier dysfunction has also been described in IBD and MC patients. […] Budesonide seems to affect the mucosal barrier function, it has anti-proliferative effects on the epithelial cells, which might impair wound healing. […] The hypothesis that gut microbiota play role in the pathogenesis of MC is interesting, however poorly studied yet. […] Overall, these are all small studies which might give a clue about a possible role of the microbiota in MC, but much larger studies are necessary to unravel the role of the gut microbiota in MC. […] The intestinal barrier function is impaired in MC patients, and this is not restored during budesonide use. This might be a cause of the high relapse rate seen for this disease.

• #67 Diagnosis and management of microscopic colitis: current perspectives | CEG

  https://www.dovepress.com/diagnosis-and-management-of-microscopic-colitis-current-perspectives-peer-reviewed-fulltext-article-CEG

  The cause of MC is not known, but is probably multifactorial. Currently, CC and LC are considered to represent specific mucosal responses to different thus-far-unidentified luminal agents in predisposed individuals, resulting in an uncontrolled mucosal immune response. […] These immunologic data support the view that MC is caused by an aberrant immune response to one or several (yet to be identified) luminal agent(s) in susceptible individuals. […] Colonic nitric oxide production is greatly increased in active CC and LC, caused by an upregulation of inducible nitric oxide synthase in the colonic epithelium. […] Epithelial barrier function has been reported to be abnormal. Increased paracellular and transcellular mucosal permeability were found in patients with CC that persisted after therapy with budesonide.

• #68 Microscopic Colitis: A Review of Collagenous and Lymphocytic Colitis – Gastroenterology & Hepatology

  https://www.gastroenterologyandhepatology.net/archives/november-2017/microscopic-colitis-a-review-of-collagenous-and-lymphocytic-colitis/

  Histology before and after ileostomy reversal found increased transcellular and tight junction permeability, proposing that mucosal barrier dysfunction has a role in CC. […] Furthermore, downregulation of the tight junction proteins claudin-4, -5, and -8, and their redistribution off the tight junction, triggered by tumor necrosis factor-α (TNF-α) and interferon-γ, contribute to diarrhea in LC. […] Medications associated with MC include nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin; selective serotonin reuptake inhibitors; proton pump inhibitors (PPIs); and drugs with various other mechanisms of action, including statins, beta blockers, angiotensin-converting enzyme inhibitors, and angiotensin receptor blockers. […] MC does not progress in a dose-dependent manner, and symptoms may be reported days to months after drug initiation, with a median time of 4 days to symptom onset. […] In summary, there is evidence to suggest that certain drugs may precipitate the onset of MC, and there should be consideration to stop these drugs to reduce the risk of relapse.

• #69 Microscopic Colitis: Epidemiology, Pathophysiology, Diagnosis and Current Management—An Update 2013

  https://pmc.ncbi.nlm.nih.gov/articles/PMC3654232/

  Using molecular techniques it was reported that in patients with microscopic colitis increased IFN-, TNF-, and IL-1 levels suggest a Th1 cytokine profile being involved in the inflammatory process. […] Environmental factors may play a crucial role in the etiology of microscopic colitis, though other than cigarette smoking presently no other such factor is confirmed. […] In addition to the inflammatory component in the pathophysiology of microscopic colitis, there may be an additional neuronal component to pathophysiology.

• #70 SciELO Brazil – Microscopic colitis: A literature review Microscopic colitis: A literature review

  https://www.scielo.br/j/ramb/a/Pg3NLNmt4FyPCHcRRnGhHBR/

  Malabsorption of bile acids was found in up to 60% of patients with LC and 44% of patients with CC, supporting the idea that this may be the cause of MC. […] Increases were also reported in interferon gamma (IFN-), tumor necrosis factor alpha (TNF-), interleukin 1 beta (IL-1), and a profile of Th1 cytokines, which are suggested to be involved in the inflammatory process. […] As for environmental factors, the major etiologic role is played by cigarettes. Smoking is more prevalent among patients with MC, and studies indicate an association with lung cancer. It has also been demonstrated that MC involvement in individuals that smoke occurs around 10 years earlier, increasing the relevance of this habit.

• #71 microscopic-colitis-pathogenesis-and-clinical-findings | Calgary Guide

  https://calgaryguide.ucalgary.ca/microscopic-colitis-pathogenesis-and-clinical-findings/microscopic-colitis-2022/

  Microscopic Colitis: Pathogenesis and clinical findings […] Release of cytokines (e.g. interferon gamma (IFN)) […] Downregulation of intestinal tight junction proteins […] Epithelial barrier function […] Transmucosal permeability […] Infiltration of bacteria or antigens […] Expression of nuclear factor kappa B (NF-kB) in colonic epithelial cells […] NF-kB increases transcriptional activity in specific genes […] Inflammatory molecules (histamine, prostaglandins, and nitric oxide) in epithelium predisposition […] Unknown trigger […] Transforming growth factor beta 1 (TGF- 1) and vascular endothelial growth factor (VEGF) expression in colonic epithelial cells […] Equilibrium shift to more production of collagen (fibrinogenesis) than breakdown (fibrinolysis) […] Drug exposure (e.g., non- steroidal anti- (+) inflammatory drugs (NSAIDs), proton pump inhibitors (PPIs))

• #72 Prevalence, Pathogenesis, Diagnosis, and Management of Microscopic Colitis

  https://www.gutnliver.org/journal/view.html?volume=12&number=3&spage=227

  Inflammatory mediators in the lamina propria resulting in surface injury have also been proposed as a cause of diarrhea. […] Exposure to a luminal antigen (medication, dietary, bile salts, bacteria) may cause an inflammatory cascade due to activation of CD8 T suppressor cells that may directly attack and damage the enterocyte. […] There is a proposed association between MC and celiac disease (CD), with an increased risk of 50- to 70-fold compared to the general population. […] CD is associated with the human leukocyte antigen (HLA) class II genes, particularly HLA DQ2 and HLA DQ8 alleles. […] Ultimately authors conclude there is an association with the HLA-DR3-DQ2 haplotype with CC and LC in patients with MC with and without CD.

• #73 microscopic-colitis-pathogenesis-and-clinical-findings | Calgary Guide

  https://calgaryguide.ucalgary.ca/microscopic-colitis-pathogenesis-and-clinical-findings/microscopic-colitis-2022/

  Inflammation and accumulation of immature subepithelial collagen matrix […] Subtype: Collagenous Colitis […] Subtype: Lymphocytic Colitis characterized by a colonic subepithelial characterized by intraepithelial collagen band on histology lymphocytic infiltrates on histology […] Microscopic Colitis […] Intestinal epithelial damage […] Malabsorption of nutrients (including bile acids) […] Weight loss […] Intestinal transmucosal permeability […] Water drawn into lumen through osmosis […] Ions and water back leak into intestinal lumen […] Non-bloody watery diarrhea […] Dehydration and electrolyte disturbances […] Continuous release of inflammatory mediators […] Peripheral afferent nerve sensitization […] Visceral hypersensitivity […] Abdominal pain.

• #74 Diagnosis and management of microscopic colitis: current perspectives | CEG

  https://www.dovepress.com/diagnosis-and-management-of-microscopic-colitis-current-perspectives-peer-reviewed-fulltext-article-CEG

  The cause of MC is not known, but is probably multifactorial. Currently, CC and LC are considered to represent specific mucosal responses to different thus-far-unidentified luminal agents in predisposed individuals, resulting in an uncontrolled mucosal immune response. […] These immunologic data support the view that MC is caused by an aberrant immune response to one or several (yet to be identified) luminal agent(s) in susceptible individuals. […] Colonic nitric oxide production is greatly increased in active CC and LC, caused by an upregulation of inducible nitric oxide synthase in the colonic epithelium. […] Epithelial barrier function has been reported to be abnormal. Increased paracellular and transcellular mucosal permeability were found in patients with CC that persisted after therapy with budesonide.

• #75 Adverse event profiles of microscopic colitis in the Japanese Adverse Drug Event Report (JADER) database | Scientific Reports

  https://www.nature.com/articles/s41598-022-22257-2

  The abnormal metabolism of NO is considered to be one of the mechanisms of diarrhea in MC; therefore, nicorandil may cause MC. […] In addition, -blockers and calcium channel blockers are also used for the treatment of angina pectoris, and a disproportionate occurrence of MC was observed in our study in users of these drugs. […] However, a drug-class effect cannot be excluded and rabeprazole and vonoprazan (which is a potassium-competitive acid blocker) can also induce MC. […] Increasing intestinal permeability induced by concomitant PPI and NSAID uses may be the underlying mechanism of MC.

• #76 microscopic-colitis-pathogenesis-and-clinical-findings | Calgary Guide

  https://calgaryguide.ucalgary.ca/microscopic-colitis-pathogenesis-and-clinical-findings/microscopic-colitis-2022/

  Microscopic Colitis: Pathogenesis and clinical findings […] Release of cytokines (e.g. interferon gamma (IFN)) […] Downregulation of intestinal tight junction proteins […] Epithelial barrier function […] Transmucosal permeability […] Infiltration of bacteria or antigens […] Expression of nuclear factor kappa B (NF-kB) in colonic epithelial cells […] NF-kB increases transcriptional activity in specific genes […] Inflammatory molecules (histamine, prostaglandins, and nitric oxide) in epithelium predisposition […] Unknown trigger […] Transforming growth factor beta 1 (TGF- 1) and vascular endothelial growth factor (VEGF) expression in colonic epithelial cells […] Equilibrium shift to more production of collagen (fibrinogenesis) than breakdown (fibrinolysis) […] Drug exposure (e.g., non- steroidal anti- (+) inflammatory drugs (NSAIDs), proton pump inhibitors (PPIs))

• #77 microscopic-colitis-pathogenesis-and-clinical-findings | Calgary Guide

  https://calgaryguide.ucalgary.ca/microscopic-colitis-pathogenesis-and-clinical-findings/microscopic-colitis-2022/

  Microscopic Colitis: Pathogenesis and clinical findings […] Release of cytokines (e.g. interferon gamma (IFN)) […] Downregulation of intestinal tight junction proteins […] Epithelial barrier function […] Transmucosal permeability […] Infiltration of bacteria or antigens […] Expression of nuclear factor kappa B (NF-kB) in colonic epithelial cells […] NF-kB increases transcriptional activity in specific genes […] Inflammatory molecules (histamine, prostaglandins, and nitric oxide) in epithelium predisposition […] Unknown trigger […] Transforming growth factor beta 1 (TGF- 1) and vascular endothelial growth factor (VEGF) expression in colonic epithelial cells […] Equilibrium shift to more production of collagen (fibrinogenesis) than breakdown (fibrinolysis) […] Drug exposure (e.g., non- steroidal anti- (+) inflammatory drugs (NSAIDs), proton pump inhibitors (PPIs))

• #78

  https://journals.lww.com/ajg/abstract/2019/10001/1487_vedolizumab_induced_remission_of_refractory.1487.aspx

  Microscopic colitis (MC) is a chronic inflammatory disease of the colon that is responsible for up to 10-15% of chronic watery diarrhea. […] While the definitive mechanism of microscopic colitis remains unknown, one of the proposed mechanisms details activation of CD8 T suppressor cells in the IEC and NF- pathway activation leading to tissue damage in epithelial cells and barrier dysfunction. The efficacy of vedolizumab in inducing MC remission supports this proposed mechanism, given its mechanism of action to bind 47-integrin and prevent T-cell adhesion.

• #79

  https://journals.lww.com/ajg/abstract/2019/10001/1487_vedolizumab_induced_remission_of_refractory.1487.aspx

  Microscopic colitis (MC) is a chronic inflammatory disease of the colon that is responsible for up to 10-15% of chronic watery diarrhea. […] While the definitive mechanism of microscopic colitis remains unknown, one of the proposed mechanisms details activation of CD8 T suppressor cells in the IEC and NF- pathway activation leading to tissue damage in epithelial cells and barrier dysfunction. The efficacy of vedolizumab in inducing MC remission supports this proposed mechanism, given its mechanism of action to bind 47-integrin and prevent T-cell adhesion.

• #80 microscopic-colitis-pathogenesis-and-clinical-findings | Calgary Guide

  https://calgaryguide.ucalgary.ca/microscopic-colitis-pathogenesis-and-clinical-findings/microscopic-colitis-2022/

  Microscopic Colitis: Pathogenesis and clinical findings […] Release of cytokines (e.g. interferon gamma (IFN)) […] Downregulation of intestinal tight junction proteins […] Epithelial barrier function […] Transmucosal permeability […] Infiltration of bacteria or antigens […] Expression of nuclear factor kappa B (NF-kB) in colonic epithelial cells […] NF-kB increases transcriptional activity in specific genes […] Inflammatory molecules (histamine, prostaglandins, and nitric oxide) in epithelium predisposition […] Unknown trigger […] Transforming growth factor beta 1 (TGF- 1) and vascular endothelial growth factor (VEGF) expression in colonic epithelial cells […] Equilibrium shift to more production of collagen (fibrinogenesis) than breakdown (fibrinolysis) […] Drug exposure (e.g., non- steroidal anti- (+) inflammatory drugs (NSAIDs), proton pump inhibitors (PPIs))

• #81

  https://www.xiahepublishing.com/2994-8754/JTG-2024-00025

  The prominent subepithelial collagen band in collagenous colitis has generated interest in aberrant collagen metabolism as a cause of the disease. Some research has demonstrated increased expression of the TGF-beta1 gene, a growth factor that can cause collagen accumulation in tissue, in patients with collagenous colitis. Another theory for the pathogenesis of microscopic colitis is that it may be medication-induced. A large population-based study found a significantly increased risk for the development of microscopic colitis in patients taking NSAIDs and PPIs compared to controls. The diarrhea in microscopic colitis is thought to arise from mucosal inflammation, supporting the idea that an intraluminal antigen plays a role in the development of symptoms. This theory is further supported by the finding that the severity of diarrhea correlates with the degree of inflammation within the lamina propria, not with the degree of subepithelial collagen band thickening.

• #82 Microscopic colitis: A common, yet often overlooked, cause of chronic diarrhea | MDedge

  https://community.the-hospitalist.org/content/microscopic-colitis-common-yet-often-overlooked-cause-chronic-diarrhea

  Another potential mechanism of MC is dysregulated collagen deposition. Collagen accumulation in the subepithelial layer in CC may result from increased levels of fibroblast growth factor, transforming growth factorbeta and vascular endothelial growth factor. Nonetheless, studies have not found an association between the severity of diarrhea in patients with CC and the thickness of the subepithelial collagen band. […] Thirdly, autoimmunity and genetic predisposition have been postulated in the pathogenesis of MC. As previously discussed, MC is associated with several autoimmune diseases and predominantly occurs in women, a distinctive feature of autoimmune disorders. Several studies have demonstrated an association between MC and HLA-DQ2 and -DQ3 haplotypes, as well as potential polymorphisms in the serotonin transporter gene promoter. It is important to note, however, that only a few familial cases of MC have been reported to date.

• #83

  https://www.xiahepublishing.com/2994-8754/JTG-2024-00025

  The prominent subepithelial collagen band in collagenous colitis has generated interest in aberrant collagen metabolism as a cause of the disease. Some research has demonstrated increased expression of the TGF-beta1 gene, a growth factor that can cause collagen accumulation in tissue, in patients with collagenous colitis. Another theory for the pathogenesis of microscopic colitis is that it may be medication-induced. A large population-based study found a significantly increased risk for the development of microscopic colitis in patients taking NSAIDs and PPIs compared to controls. The diarrhea in microscopic colitis is thought to arise from mucosal inflammation, supporting the idea that an intraluminal antigen plays a role in the development of symptoms. This theory is further supported by the finding that the severity of diarrhea correlates with the degree of inflammation within the lamina propria, not with the degree of subepithelial collagen band thickening.

• #84 Microscopic Colitis: A Review of Collagenous and Lymphocytic Colitis – Gastroenterology & Hepatology

  https://www.gastroenterologyandhepatology.net/archives/november-2017/microscopic-colitis-a-review-of-collagenous-and-lymphocytic-colitis/

  Microscopic colitis (MC) is a chronic inflammatory bowel disease characterized by chronic watery diarrhea and diagnosed with the histologic hallmarks of disease despite a macroscopically normal large bowel. […] It is probable that the innate immune response and environmental exposures contribute to pathogenesis in an interdependent manner in genetically susceptible individuals. […] In CC, collagen accumulation in the subepithelial layer reflects disturbance in the homeostasis of the extra-cellular matrix and is predominantly driven by attenuated matrix degradation and tissue inhibitor of metalloproteinase-1 (TIMP-1) imbalance. This inhibits several metalloproteinases involved in collagen degradation and upregulation of transforming growth factor-β, which contributes to fibrogenesis and collagen deposition.

• #85 Microscopic colitis—microbiome, barrier function and associated diseases

  https://atm.amegroups.org/article/view/14674/html

  Microscopic colitis (MC) is a chronic inflammatory bowel disease (IBD) with little in terms of endoscopic abnormalities and is frequently associated with other autoimmune diseases. […] The pathogenesis of MC is complex, multifactorial and poorly understood. Current concepts revolve around innate immunity or microbiome alterations as well as gut barrier dysfunction, all of which lead to the development of subtle inflammatory lesions in gut mucosa. […] The results of numerous basic and clinical studies involving molecular techniques as well as advanced endoscopic imaging revealed the important role of both intrinsic (e.g., hormonal) as well as extrinsic (e.g., NSAIDs and PPIs) factors in the modulation of gastrointestinal microbiome and MC pathogenesis. […] The pathophysiological cause of MC is unknown, but recent hypotheses revolve around mucosal inflammation, microbiome and gut barrier alterations. Several extrinsic (environmental) as well as intrinsic (endocrine) factors might play a role in the pathogenesis of the disease.

• #86 Microscopic colitis—microbiome, barrier function and associated diseases

  https://atm.amegroups.org/article/view/14674/18553

  Microscopic colitis (MC) is a chronic inflammatory bowel disease (IBD) with little in terms of endoscopic abnormalities and is frequently associated with other autoimmune diseases. […] The pathogenesis of MC is complex, multifactorial and poorly understood. Current concepts revolve around innate immunity or microbiome alterations as well as gut barrier dysfunction, all of which lead to the development of subtle inflammatory lesions in gut mucosa. […] The results of numerous basic and clinical studies involving molecular techniques as well as advanced endoscopic imaging revealed the important role of both intrinsic (e.g., hormonal) as well as extrinsic (e.g., NSAIDs and PPIs) factors in the modulation of gastrointestinal microbiome and MC pathogenesis. […] The pathophysiological cause of MC is unknown, but recent hypotheses revolve around mucosal inflammation, microbiome and gut barrier alterations. Several extrinsic (environmental) as well as intrinsic (endocrine) factors might play a role in the pathogenesis of the disease.

• #87 Microscopic Colitis: New PPI Data – Gastroenterology Advisor

  https://www.gastroenterologyadvisor.com/features/microscopic-colitis-new-ppi-data/

  The exact pathophysiology of microscopic colitis is not completely understood, though PPIs and NSAIDs are 2 medications commonly implicated for triggering the inflammatory process. […] The exact pathophysiology is not completely understood and may be multifactorial, with possible contributions by autoimmunity, hormone levels, dysregulation of the colonic mucosa and immune system (including the gut microbiome), and a genetic predisposition. […] It has been postulated that PPIs may lead to MC via reduction of gastric acidity, which causes changes in the gut microbiome and electrolyte concentration within the colonic lumen. These changes could induce intraepithelial lymphocytosis and subsequently inflammation and resulting diarrhea. […] NSAIDs may predispose patients to developing MC based on their pharmacologic mechanism of inhibiting cyclooxygenase, leading to disruptions in the colonic mucosal barriers and increased translocation of potential bacteria and toxins.

• #88

  https://www.xiahepublishing.com/2994-8754/JTG-2024-00025

  Given the poorly understood and likely multifactorial mechanism through which microscopic colitis develops, the pathogenesis is generally accepted to involve genetically predisposed individuals who undergo an increased inflammatory response to intraluminal antigens. Studies have shown an association with the human leukocyte antigen (HLA) gene complex in the development of microscopic colitis, with the HLA-DQ2 and HLA-DQ1,3 genes most strongly implicated. However, the exact extent to which genetic predisposition plays a role remains unclear. The HLA-DQ2 and DQ3 haplotype is known to be a predisposing factor in patients with Celiac disease, and their association with microscopic colitis supports the idea that autoimmunity could be a key component in the pathogenesis of microscopic colitis. Due to the shared haplotypes, it has even been posited that microscopic colitis may result from gluten sensitivity, as seen in Celiac disease.

• #89

  https://link.springer.com/article/10.1007/s40266-023-01094-6

  The pathogenesis of microscopic colitis is complex and multifactorial, and involves innate and adaptive immune responses to luminal antigens, genetic risk factors, and autoimmunity, as well as extracellular matrix alterations, all of which contribute by varied mechanisms to watery diarrhea […] The disease has been reported to have an increasing incidence, and its incidence may, in some geographical areas, exceed those of ulcerative colitis and Crohns disease among elderly individuals. Microscopic colitis is associated with ulcerative colitis and Crohns disease in the umbrella diagnosis of inflammatory bowel disease (IBD). […] Although the etiology of microscopic colitis has not yet been clarified, autoimmune diseases and medications may trigger an imbalanced mucosal immune response in the colon of genetically predisposed individuals, which may aid in the emergence of microscopic colitis. Thus, microscopic mucosal inflammation is likely to be the cause of the diarrhea that accompanies microscopic colitis.

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