Materiały źródłowe

• #1

  https://link.springer.com/article/10.1007/s43472-024-00130-z

  Anal pruritus is a frequent disorder accounting for many proctological consultations, affecting mainly middle-aged males. […] It is believed that it implies a vicious circle of itching and scratching, increasing irritation and inflammation, and thus symptoms. […] Physiopathology of anal pruritus is not fully understood. It is supposed to be initiated by Cfibres in the skin, with the implication of itching mediators such as bradykinin, histamine and kallikrein. […] It is believed that it implies a vicious circle of itching and scratching, increasing irritation and inflammation, and thus symptoms. […] About 100 possible causes have been identified. […] Main secondary causes can be classified into local irritation, infections, proctological diseases, neoplastic lesions, dermatological and systemic diseases, and other aetiologies.

• #2 Pruritus Ani

  https://pmc.ncbi.nlm.nih.gov/articles/PMC4755774/

  Pruritus ani is a common condition with many different potential causes. […] The pathophysiology of itching in general is thought to be related to the C-fibers in the skin. Histamine, bradykinin, and kallikrein, among other substances, have been implicated in itching. […] Causes of pruritus ani can be roughly classified into secondary and idiopathic, with 25 to 75% attributed to an identifiable source. […] Local irritation is one of the main causes of pruritus ani. […] Several infections are known to cause pruritus ani. […] Inflammatory conditions include systemic skin processes that can affect the perianal region, in addition to other parts of the body. […] Several systemic diseases can present with generalized pruritus as well as pruritus ani. […] Any anal or perianal neoplasm can present with symptoms of pruritus ani, and up to half of patients with perianal Paget’s or Bowen’s disease have pruritus.

• #3 Itch – Wikipedia

  https://en.wikipedia.org/wiki/Itch

  Inflammatory mediators such as bradykinin, serotonin (5-HT) and prostaglandins released during a painful or pruritic inflammatory condition not only activate pruriceptors but also cause acute sensitization of the nociceptors. […] Noxious input to the spinal cord is known to produce central sensitization, which consists of allodynia, exaggeration of pain, and punctuate hyperalgesia, extreme sensitivity to pain.

• #4 Basic Mechanisms of Itch

  https://pmc.ncbi.nlm.nih.gov/articles/PMC3170689/

  Chronic itch represents a burdensome clinical problem that can originate from a variety of etiologies. Pruriceptive itch originates following the activation of peripheral sensory nerve endings following damage or exposure to inflammatory mediators and ascends to the brain through the spinal thalamic tract. […] More than one sensory nerve subtype is thought to subserve pruriceptive itch which includes both unmyelinated C-fibers and thinly myelinated A nerve fibers. […] Studies have demonstrated that both peripheral and central sensitization to pruritogenic stimuli occur during chronic itch. […] Pruriceptive itch originates when specific sensory nerve terminals, generally located in the skin, are activated. […] The excitation of sensory nerve fibers in the skin leading to pruriceptive itch occurs upon exposure of certain sensory nerve terminals to a pruritic substance and frequently follows skin damage or inflammation.

• #5 Itch, pruritus

  https://dermnetnz.org/topics/pruritus

  Itch, like pain, can originate anywhere along the neural itch pathway, from the central nervous system (brain and spinal cord) to the peripheral nervous system and the skin. […] Mechanisms underlying pruritus are complex. […] The itch signal is transmitted mainly through small, itch-selective C-fibres in the skin in addition to histamine-triggered and non-histaminergic neurons. […] Patients with chronic pruritus usually have both peripheral and central hypersensitisation (a heightened reaction) which means they tend to overreact to noxious stimuli which normally inhibit itch (such as heat and scratching) and also misinterpret non-noxious stimuli as an itch (eg, light touch). […] The way scratching stops itching has been explained by an interaction with pain pathways within the dorsal horn of the spinal cord.

• #6 Itch – Wikipedia

  https://en.wikipedia.org/wiki/Itch

  Itch can originate in the peripheral nervous system (dermal or neuropathic) or in the central nervous system (neuropathic, neurogenic, or psychogenic. […] Itch originating in the skin is known as pruritoceptive, and can be induced by a variety of stimuli, including mechanical, chemical, thermal, and electrical stimulation, or infection. The primary afferent neurons responsible for histamine-induced itch are unmyelinated C-fibres. […] Two major classes of human C-fibre nociceptors exist: mechano-responsive nociceptors and mechano-insensitive nociceptors. Mechano-responsive nociceptors have been shown in studies to respond to mostly pain, and mechano-insensitive receptors respond mostly to itch induced by histamine. However, it does not explain mechanically induced itch or itch produced without a flare reaction that involves no histamine.

• #7 Itch – Wikipedia

  https://en.wikipedia.org/wiki/Itch

  Studies have been done to show that itch receptors are found only on the top two skin layers, the epidermis and the epidermal/dermal transition layers. […] Itch is often classified as that which is histamine mediated (histaminergic) and nonhistaminergic. […] Itch is readily abolished in skin areas treated with nociceptor excitotoxin capsaicin but remains unchanged in skin areas rendered touch insensitive by pretreatment with anti-inflammatory saponins. […] Using single-cell mRNA sequencing, clusters of genes expressed in itch-related tissues were identified, e.g. NP1-3, transmitting itch information; where NP3 expresses neuropeptides Nppb and Sst as well as genes involved in inflammatory itch (Il31ra, Osmr and Crystrl2). […] Staphylococcus aureus, a bacterial pathogen associated with itchy skin diseases, directly activates pruriceptor sensory neurons to drive itch. Skin exposure to S. aureus causes robust itch and scratch-induced damage. This reaction is mediated by S. aureus serine protease V8 which cleaves proteinase-activated receptor 1 (PAR1) on mouse and human sensory neurons.

• #8 Basic Mechanisms of Itch

  https://pmc.ncbi.nlm.nih.gov/articles/PMC3170689/

  Studies in humans and non-human primates have demonstrated that slowly conducting unmyelinated nerve fibers (i.e. C-fibers) detect and signal pruriceptive information to the central nervous system. […] The complexity regarding the specific subtypes of sensory nerves transducing pruriceptive itch exists because more than one nerve subtype is activated by substances that cause itch. […] Sensory nerve fibers and spinal cord neurons that respond to itch-producing stimuli also respond to noxious or potentially damaging stimuli, how the nervous system processing itch versus noxious or pain-producing stimuli remains puzzling. […] Following activation of peripheral sensory nerve endings of DRG neurons by itch producing stimuli, the central nerve terminals of these neurons form synapses on second-order neurons located in the dorsal horn of the spinal cord.

• #9 Basic Mechanisms of Itch

  https://pmc.ncbi.nlm.nih.gov/articles/PMC3170689/

  The loss of itch sensation indicates that, like pain and temperature sensation, pruriception ascends to the brain via the anteriolateral quadrant of the spinal cord in the spinal thalamic tract (STT). […] Electrophysiological studies of STT neurons from non-human primates reveal that they are activated in response to both histamine and cowhage applied to the skin. […] Pruriceptive STT neurons were found to project to the posterior and ventral posterior regions of the thalamus in non-human primates and cats. […] The mechanisms underlying how pruritogenic mediators affect sensory neuron excitability will be highlighted below in reference to both humans and experimental animals.

• #10 Itch – Wikipedia

  https://en.wikipedia.org/wiki/Itch

  After the pruriceptive primary afferent has been activated, the signal is transmitted from the skin into the spinal dorsal horn. In this area, a number of interneurons will either be inhibited or activated to promote activation of projection neurons, mediating the pruriceptive signal to the brain. […] Neuropathic itch can originate at any point along the afferent pathway as a result of damage of the nervous system. […] Neurogenic itch, which is itch induced centrally but with no neural damage, is mostly associated with increased accumulation of exogenous opioids and possibly synthetic opioids. […] Itch is also associated with some symptoms of psychiatric disorders such as tactile hallucinations, delusions of parasitosis, or obsessive-compulsive disorders (as in OCD-related neurotic scratching).

• #11 Itching – Dermatologic Disorders – Merck Manual Professional Edition

  https://www.merckmanuals.com/professional/dermatologic-disorders/approach-to-the-dermatologic-patient/itching

  Itch can be prompted by diverse stimuli, including light touch, vibration, and wool fibers. There are a number of chemical mediators as well as different mechanisms by which the sensation of itch occurs. Specific peripheral sensory neurons mediate the itch sensation. These neurons are distinct from those that respond to light touch or pain; they contain a receptor, MrgA3, the stimulation of which causes the sensation of itching. […] There are 3 mechanisms of itch: Dermatologic: This mechanism is typically caused by inflammatory or pathologic processes (eg, urticaria, eczema). […] Systemic: This mechanism is related to diseases of organs other than skin (eg, cholestasis). […] Neurogenic: This mechanism is related to disorders of the central or peripheral nervous system (eg, multiple sclerosis).

• #12 Itch, pruritus

  https://dermnetnz.org/topics/pruritus

  Uraemic pruritus arises in patients undergoing dialysis is due to a combination of xerosis (dry skin), secondary hyperparathyroidism, peripheral neuropathy (nerve changes) and inflammation. […] Once chronic pruritus has occurred, there may be secondary changes in the nerves in the skin and central nervous system which heighten the sensation of itch. […] Cholestasis is thought to release toxic substances from the liver, which stimulates neural itch fibres in the skin. […] In Hodgkin lymphoma, pruritus is thought to be caused by histamine release, which may be related to eosinophilia. […] In chronic hepatitis C infection, the mechanisms responsible for itch remain unclear. […] The management of chronic severe itch is difficult and often requires the use of combination therapy over a long period of time.

• #13 Helicobacter Pylori infection and Persistent Itching ‎

  https://www.aeji.journals.ekb.eg/article_182154.html

  Among patients with persistent itching recruited in the current study, 46.4% had an evidence of H pylori infection. […] H pylori positive cases with persistent itching did not have elevated Ig E levels. […] Out of 130 H pylori positive cases 60% had complete resolution of itching after treatment of H pylori. […] H pylori have been linked to many skin diseases in many epidemiological studies as well as clinical ones. […] The link of skin diseases mainly pruritic skin diseases among H pylori patients have been attributed to many mechanisms. […] It seems that following the prolonged infection with H pylori, an interaction with the host immune system do occur. […] The lack of Ig E detection among H pylori patients with pruritis in this study may favor this assumption. […] The common causes of itching usually seen in our community e.g. liver diseases and thyroid dysfunction were ruled out.

• #14 Helicobacter Pylori infection and Persistent Itching ‎

  https://www.aeji.journals.ekb.eg/article_182154.html

  This favors the hypothesis that H pylori is presumably a direct cause of itching and the link is not just an epidemiological association. […] The lack of Ig E positivity among our H pylori positive cohort (0%, P 0.001) favors the possibility that a direct non-allergic mechanism stands behind. […] We believe that both the high frequency of H pylori among patients with persistent itching and the high (60%) itching relief rate reported in the current study would alarm both dermatologists and gastroenterologists in our developing countries to consider H pylori in the differential diagnosis.

• #15 Helicobacter Pylori infection and Persistent Itching ‎

  https://aeji.journals.ekb.eg/article_182154.html

  Helicobacter (H) pylori is a worldwide prevalent infection with wide range of gastric and extra-gastric diseases. The current study aimed at determining the frequency of H pylori among patients with persistent itching and evaluates impact of H pylori treatment on the course of the disease. Among patients with persistent itching recruited in the current study, 46.4% had an evidence of H pylori infection. H pylori positive cases with persistent itching did not have elevated Ig E levels. Out of 130 H pylori positive cases 60% had complete resolution of itching after treatment of H pylori. H pylori have been linked to many skin diseases in many epidemiological studies as well as clinical ones. The link of skin diseases mainly pruritic skin diseases among H pylori patients have been attributed to many mechanisms. The most widely accepted is autoimmune one. It seems that following the prolonged infection with H pylori, an interaction with the host immune system do occur. H pylori trigger antigens that cross-react with T cells and provoke autoantibodies resulting in loss of tolerance to self-antigens in the skin. The lack of Ig E positivity among our H pylori positive cohort (0%, P 0.001) favors the possibility that a direct non-allergic mechanism stands behind. We believe that both the high frequency of H pylori among patients with persistent itching and the high (60%) itching relief rate reported in the current study would alarm both dermatologists and gastroenterologists in our developing countries to consider H pylori in the differential diagnosis.

• #16 Itchy Bottom (Pruritus Ani): Causes and Treatment

  https://patient.info/skin-conditions/itchy-bottom-pruritus-ani

  Skin conditions cause about half of all cases of secondary pruritus ani. […] Persistent scratching of the anal skin can damage the skin and make it more likely to develop a skin infection in that area. […] A 'vicious circle’ (itch-scratch cycle) sometimes develops. The more you scratch, the more irritated the skin becomes and the more it itches. […] If a cause for the itchy bottom (pruritus ani) can be identified, it is easier to treat and relieve your symptoms. Most people respond well to treatment for an itchy bottom. However, in some people it can become a persistent (chronic) problem.

• #17 Itching – Dermatologic Disorders – Merck Manual Professional Edition

  https://www.merckmanuals.com/professional/dermatologic-disorders/approach-to-the-dermatologic-patient/itching

  Intense itching stimulates vigorous scratching, which in turn can cause secondary skin conditions (eg, inflammation, excoriation, infection), which can lead to more itching through disruption of the skin barrier. Although scratching can temporarily reduce the sensation of itch by activating inhibitory neuronal circuits, it also leads to amplification of itching at the level of the brain, exacerbating the itchscratch cycle.

• #18 Anal Itching – What’s The Deal? – Dr. Chutkan

  https://gutbliss.com/anal-itching-whats-the-deal/

  Daniel, anal itching is a common – and frustrating – problem, and people are often embarrassed to talk about it, so thank you for asking! You mention two things that might be clues to the cause of your anal itching – coffee and loose eliminations. Coffee is one of a number of foods that can cause irritation to the anus that’s manifest as itching. The mechanism might be a slight loosening of the anal sphincter that allows a small amount of stool to leak out and irritate the area. […] Some other things to think about that may be causing your anal itching: Fungal overgrowth, especially if you’ve recently been on antibiotics or keep damp clothing on after exercise. Anal fissures, which can result from constipation or be associated with more serious conditions like Crohn’s disease. Hemorrhoids, which can result from straining or frequent bowel movements. Stool leakage, or incomplete wiping, resulting in some residual stool in the area. Parasites like pinworm which often cause itching at night when the worms move to the anal area to lay their eggs.

• #19 Approach to the patient with anal pruritus – UpToDate

  https://www.uptodate.com/contents/approach-to-the-patient-with-anal-pruritus

  Itching of the anus or perianal skin is a common disorder usually arising from benign conditions. This topic will review the etiology, diagnostic approach, and management of patients with anal pruritus. […] Approximately 75 percent of cases of anal pruritus are secondary to inflammatory, infectious, systemic, neoplastic, and anorectal disorders that contribute to or underlie the development of pruritus. […] Anorectal diseases associated with anal pruritus include prolapsed internal hemorrhoids, abscesses, fissures, and fistulas. […] Anal pruritus can also result from a variety of inflammatory skin disorders.

• #20 Researchers Identify Mechanism Underlying Allergic Itching, and Show It Can Be Blocked | Mass General Brigham

  https://www.massgeneralbrigham.org/en/about/newsroom/press-releases/researchers-identify-mechanism-underlying-allergic-itching

  Our research provides one explanation for why, in a world full of allergens, one person may be more likely to develop an allergic response than another, said senior and corresponding author Caroline Sokol, MD, PhD, an attending physician in the Allergy and Clinical Immunology Unit at MGH, and assistant professor of medicine at Harvard Medical School. By establishing a pathway that controls allergen responsiveness, we have identified a new cellular and molecular circuit that can be targeted to treat and prevent allergic responses including itching. […] The researchers found that a poorly understood specific immune cell type in the skin, that they called GD3 cells, produce a molecule called IL-3 in response to environmental triggers that include the microbes that normally live on the skin. IL-3 acts directly on a subset of itch-inducing sensory neurons to prime their responsiveness to even low levels of protease allergens from common sources like house dust mites, environmental molds and mosquitos. IL-3 makes sensory nerves more reactive to allergens by priming them without directly causing itchiness. The researchers found that this process involves a signaling pathway that boosts the production of certain molecules, leading to the start of an allergic reaction.

• #21 Researchers Identify Mechanism Underlying Allergic Itching, and Show It Can Be Blocked | Mass General Brigham

  https://www.massgeneralbrigham.org/en/about/newsroom/press-releases/researchers-identify-mechanism-underlying-allergic-itching

  Our data suggest that this pathway is also present in humans, which raises the possibility that by targeting the IL-3-mediated signaling pathway, we can generate novel therapeutics for preventing an allergy, said Sokol. Even more importantly, if we can determine the specific factors that activate GD3 cells and create this IL-3-mediated circuit, we might be able to intervene in those factors and not only understand allergic sensitization but prevent it.

• #22

  https://link.springer.com/article/10.1007/s43472-024-00130-z

  Psychological factors can also be implied. […] Treatment should be directed through whatever causing factor that has been identified. […] When dietary or lifestyle measures remain insufficient, local treatments can be applied, such as mild steroid creams for short periods. […] It is believed that systemic neuromodulators could be a possible treatment, but more research on anal pruritus physiopathology is needed to find new targets. […] Another treatment that was studied is perianal intradermal injection of methylene blue. This destroys nerve endings and reduces anal itching but can be associated with severe complications such as full-thickness skin necrosis. […] Treatment strategies must often be escalated until a good regimen is found, which can be a long road for the patient and the clinician. […] Anal pruritus is a common source of proctological consultations, and the appropriate management depends on the identification of a potential secondary cause through rigorous history taking, physical examination and directed complementary investigations.

• #23 Itchy Bottom (Pruritus Ani): Causes and Treatment

  https://patient.info/skin-conditions/itchy-bottom-pruritus-ani

  An itchy bottom (pruritus ani) is a persistent itch around the anus. There are many different causes, like haemorrhoids, skin conditions, or infections. Treatments depend on the cause, but include hygiene measures and creams or ointments to treat the itching. […] Pruritus ani is the medical term for a persistent (chronic) itchy feeling around the anus, or an itch in the anus. The main symptom is an urge to scratch your anus, which is difficult to resist. […] Various conditions may cause an itchy bottom. When the cause is another condition which has been identified, this is known as secondary pruritus ani. However, in many cases the cause is not clear. This is called 'idiopathic pruritus ani’ which means 'itchy anus of unknown cause’. Up to 90% of cases of pruritus ani may be idiopathic.

• #24 Pruritus Ani

  https://pmc.ncbi.nlm.nih.gov/articles/PMC4755774/

  Primary or idiopathic pruritus is invoked when no specific pathologic etiology can be blamed for the patient’s symptoms. […] The quality of evidence for regimens to treat pruritus ani ranges from none to scantfew rigorous trials exist to favor one therapy over another. […] Initial treatment should be directed toward any secondary causes identified. […] The patient should be admonished not to scratch the area, as this may lead to more excoriation and irritation. […] In severe cases of soilage or irritation, Berwick’s solution (crystal violet 1%, brilliant green 1%, 95% ethanol 50%, distilled water as much as sufficient 100%) can be applied followed by cool air drying. […] Capsaicin, a component of chili peppers, has been suggested as a treatment of pruritus due to its ability to suppress histamine release and the subsequent itchscratch response.

• #25 Pruritus Ani

  https://pmc.ncbi.nlm.nih.gov/articles/PMC4755774/

  There is some suggestion that topical application of tacrolimus ointment for 4 weeks may decrease itch intensity and frequency in pruritus ani. […] Topical cortisone cream can also decrease itching symptoms. […] For refractory cases of pruritus ani, intradermal and subcutaneous injection (tattooing) of the perianal region with methylene blue has been described in several small case series. […] Pruritus ani is a common condition with a myriad of etiologies.

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