Materiały źródłowe

• #1 Diagnosis – The Myositis Association

  https://www.myositis.org/about-myositis/diagnosis/

  Diagnosing any disease is a bit like solving a mystery. For those with myositis, this process can be challenging for a number of reasons. Myositis diseases are rare, which means that clinicians may not be immediately aware of what to look for. Myositis often starts out looking like a number of different autoimmune diseases. Myositis takes a number of different forms, each of which is also very diverse. Myositis can occur in combination with other overlapping autoimmune diseases. Myositis symptoms are different in every patient. The first step in any diagnosis is a medical history. The doctor will ask questions about your health in general, including detailed personal and family health histories. The next step will be a physical examination. The history and physical will give the doctor some idea about a diagnosis. He or she may then use one or more of the following tests to help confirm a specific diagnosis: Blood tests, especially the levels of certain muscle enzymes in the blood, can offer important clues, not only about what may be causing symptoms, but also what is not causing them. Diagnostic tests are typically ordered after blood tests are done to gather additional information. Muscle and skin biopsy are often the most definitive way to diagnose myositis diseases. Other diagnostic tests may be done to further clarify the diagnosis or to rule out another disease or condition that has symptoms similar to myositis. Many myositis patients are diagnosed only after visiting many health professionals. If you or your physician believe your disease is not progressing or responding as expected, the next step may be a consultation with another physician, especially one who specializes in myositis.

• #1 Blood Tests – The Myositis Association

  https://www.myositis.org/about-myositis/diagnosis/blood-tests/

  Aldolase is an enzyme found especially in the liver and skeletal muscles. When the liver or muscles are damaged, the cells release their contents (including aldolase) into the bloodstream. Since muscle weakness can be caused by problems with either the nerves or the muscles, this test identifies weakness caused by muscular problems. Aldolase will not change when weakness is caused by neurological problems. […] Antinuclear Antibodies (also known as ANA) is a screening blood test to determine if you have an autoimmune disease. […] A positive ANA will not, however, identify the specific disease. Moreover, a negative test does not rule out myositis. […] Creatine Kinase (also known as CK, or Creatine Phosphokinase [CPK]) is an important diagnostic blood test for myopathies. […] Higher levels of serum CK can indicate muscle damage from chronic disease or acute muscle injury. In myositis, it is not uncommon for CK levels to far exceed the upper limit of normal.

• #1 Myositis: Laboratory Support for Classification and Diagnosis | Clinical Focus | Quest Diagnostics Myositis: Laboratory Support for Classification and DiagnosisMyositis: Laboratory Support for Classification and Diagnosis

  https://testdirectory.questdiagnostics.com/test/test-guides/CF_Myositis/myositis-laboratory-support-for-classification-and-diagnosis

  Quest Diagnostics offers tests and panels that may be useful for classifying or diagnosing myositis. […] On initial evaluation, about 80% to 90% of myositis patients have elevated creatine kinase (CK) associated with muscle damage. Using elevated CK to diagnose IIMs has limitations, however. CK levels may be only slightly elevated, or normal, due to lack of muscle mass or the presence of circulating CK inhibitors or CK antibodies. Normal CK levels may also be observed in patients with IBM, as well as those with juvenile or amyopathic dermatomyositis. Another limitation is that CK and other muscle enzymes are not specific markers of polymyositis/dermatomyositis. Serum elevations may be due to other types of muscle disease (muscular dystrophies, rhabdomyolysis), hypothyroidism, cardiac, or liver disease. Consequently, tests employing antibody markers, rather than muscle enzymes, are used to specifically diagnose and classify IIMs.

• #1 Blood Tests – The Myositis Association

  https://www.myositis.org/about-myositis/diagnosis/blood-tests/

  If the CK test indicates muscle damage, more tests will be needed to find exactly where the muscle damage occurred. […] Myositis autoantibodies are an important diagnostic and predictive tool. They are identified through a special blood test that tests for a whole panel of autoantibodies that are related to myositis diseases.

• #1 Myositis Autoantibodies – Myositis Support and Understanding

  https://understandingmyositis.org/myositis-antibody-testing/

  A diagnosis of one of the Idiopathic Inflammatory Myopathies (IIM), or Myositis, can be made through various methods including clinical and physical exam, thorough patient history, blood work, EMG, MRI, and often, a muscle or skin biopsy. […] When IIM is part of the differential diagnosis, Myositis-Specific Antibodies (MSA) should also be a part of the testing. […] An estimated 50% of patients with Polymyositis or Dermatomyositis have one of the known Myositis-Specific Antibodies. […] Myositis-Specific Antibodies (MSA) have also improved our understanding of myositis by leading to the identification of certain clinical patterns. […] MSAs can assist your doctor in helping to confirm a diagnosis of certain types of Myositis such as Polymyositis and Dermatomyositis. […] It is estimated that 50% of patients with Polymyositis or Dermatomyositis have Myositis-Specific Antibodies (MSA), so when a clinical exam and other testing suggest the possibility of Myositis, the presence of these antibodies can be supporting evidence for a diagnosis.

• #1 Myositis: Laboratory Support for Classification and Diagnosis | Clinical Focus | Quest Diagnostics Myositis: Laboratory Support for Classification and DiagnosisMyositis: Laboratory Support for Classification and Diagnosis

  https://testdirectory.questdiagnostics.com/test/test-guides/CF_Myositis/myositis-laboratory-support-for-classification-and-diagnosis

  The classical myositis-specific antibodies include Jo-1, EJ, OJ, PL-7, and PL-12 synthetase antibodies, which define antisynthetase syndrome, as well as Mi-2 and SRP antibodies. Of these, only Jo-1 antibody is currently included in the EULAR/ACR criteria. Jo-1 antibody is observed in 21% of patients with polymyositis and in 11% of those with antisynthetase syndrome with dermatomyositis-like rash. Because it is 100% specific for IIM, Jo-1 positivity is a major contributor to a definitive IIM diagnosis. The remaining classical myositis-specific antibodies occur less frequently than Jo-1 but are also highly specific (97%-100%) for IIM. Accordingly, a positive test result for any of the classical myositis-specific antibodies is highly suggestive of IIM. A negative test result does not rule out IIM; classical myositis-specific antibodies are not detected in 50% of affected patients.

• #1 Myositis: Laboratory Support for Classification and Diagnosis | Clinical Focus | Quest Diagnostics Myositis: Laboratory Support for Classification and DiagnosisMyositis: Laboratory Support for Classification and Diagnosis

  https://testdirectory.questdiagnostics.com/test/test-guides/CF_Myositis/myositis-laboratory-support-for-classification-and-diagnosis

  Myositis-specific antibodies for IBM and IMNM have been more recently described: cN-1A antibodies target cytosolic 5′-nucleotidase and have been reported to be highly predictive for IBM with high specificity (87%-100%) but wide ranging sensitivity estimates (33%-76%). HMGCR antibodies target 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR); positive results correctly identify nearly 100% of patients with IMNM. However, sensitivity for IMNM is about 45%. […] Myositis-associated antibodies, Ku, PM/Scl, Sjögren’s antibody [SS-A], and Smith [Sm]/U1-RNP antibody, are less specific for polymyositis and dermatomyositis and are found in 1% to 13% of these patients. A positive test result for a myositis-associated antibody in a symptomatic patient suggests the presence of either polymyositis, dermatomyositis (with rash), IMNM, or IBM; overlap myositis is also a possibility.

• #1 How to diagnose Myositis? – Myositis Support and Understanding

  https://understandingmyositis.org/diagnose-myositis/

  A muscle biopsy is performed to assess the musculoskeletal system for abnormalities. […] The muscle biopsy is considered the gold standard in diagnosing myositis and can rule out other diseases. […] A positive skin sample can confirm the diagnosis of Dermatomyositis and rule out other disorders, such as Lupus. […] An MRI gives a cross-section image of muscles in a specific area to show if inflammation exists. […] Because of a high cancer risk found in some forms of Myositis, both before and after diagnosis, doctors will often perform cancer screenings at the onset or suspicion of Myositis. […] The International Myositis Classification Criteria Project (IMCCP), after many years of hard work, and composed of a large number of prominent myositis physicians and researchers across the globe, developed these evidence-based criteria for both adult and juvenile forms of myositis.

• #1 Polymyositis – Diagnosis and treatment – Mayo Clinic

  https://www.mayoclinic.org/diseases-conditions/polymyositis/diagnosis-treatment/drc-20353212

  If your doctor suspects you have polymyositis, he or she might suggest some of the following tests: […] A blood test will let your doctor know if you have elevated levels of muscle enzymes, which can indicate muscle damage. A blood test can also detect specific autoantibodies associated with different symptoms of polymyositis, which can help in determining the best medication and treatment. […] This test involves inserting a thin needle electrode through the skin into the muscle. Electrical activity is measured as you relax or tighten the muscle, and changes in the pattern of electrical activity can confirm a muscle disease. The doctor can determine the distribution of the disease by testing different muscles. […] A scanner creates cross-sectional images of your muscles from data generated by a powerful magnetic field and radio waves. Unlike a muscle biopsy, an MRI can assess inflammation over a large area of muscle.

• #1 Myositis | Radiology Reference Article | Radiopaedia.org

  https://radiopaedia.org/articles/myositis-2?lang=us

  Myositis (plural: myositides) is the subset of myopathy characterized by inflammation of skeletal muscle. […] MRI is the gold standard modality for non-invasive evaluation of myositis, which shows a classic edema signal pattern (high T2WI and STIR signal) in affected muscles. Inflamed muscles demonstrate contrast enhancement. […] If chronic, T1WI will show high muscle signal indicating fat replacement and atrophy.

• #1 Myositis: Symptoms, Causes, Diagnosis and Treatments

  https://www.webmd.com/a-to-z-guides/myositis-symptoms-treatments-prognosis

  Myositis Diagnosis […] A doctor may suspect myositis based on symptoms such as muscle weakness or other signs of inflammation. To confirm the diagnosis, they might order several tests, including: […] Blood tests. High levels of muscle enzymes, such as creatine kinase, may mean there is muscle inflammation. Other myositis blood tests can check for abnormal antibodies that may identify an autoimmune condition. […] MRI scan. An MRI scanner uses a powerful magnet and a computer to create detailed images of your muscles. It can help show areas that are inflamed and track changes in the muscles over time. […] Electromyography (EMG). During an EMG, a doctor inserts tiny needle electrodes into your muscles to measure how they respond to electrical nerve signals. This test can help spot muscles that are weak or damaged.

• #1 Diagnosis and management of inflammatory muscle disease

  https://www.hcplive.com/view/diagnosis-and-management-inflammatory-muscle-disease

  The third step is to elicit any associated symptoms. […] The physician should assess all muscle groups, noting that the weakness in most idiopathic inflammatory myopathies is proximal (shoulder, neck, and pelvic girdle muscle) and symmetrical. […] Although serum elevations of aldolase, aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase can be seen in myopathic disease, elevation of the creatine kinase (CK) level is thought to be the most sensitive laboratory test result related to skeletal muscle damage. […] Although elevated CK levels are seen in most cases of inflammatory myopathy, CK levels may be minimally elevated or even normal in inclusion body myositis, myositis associated with neoplasia, and early presentations of polymyositis and dermatomyositis and when significant muscle atrophy has developed.

• #1 Diagnosis, pathogenesis and treatment of myositis: recent advances

  https://pmc.ncbi.nlm.nih.gov/articles/PMC3927896/

  Dermatomyositis (DM), polymyositis (PM), necrotizing myopathy (NM) and inclusion body myositis (IBM) are four distinct subtypes of idiopathic inflammatory myopathies in short myositis. […] Muscle biopsy is indispensable for making a reliable diagnosis. […] The use of magnetic resonance imaging of skeletal muscles and detection of myositis-specific autoantibodies have become useful additions to our diagnostic repertoire. […] Diagnosis is based on the clinical examination (distribution of paresis) in combination with laboratory values, including creatine kinase (CK) and autoantibodies, electromyography (EMG) and the histopathology of the skeletal muscle. […] A biopsy is indispensable to distinguish PM from other myopathies. […] A biopsy is required to make the diagnosis. […] A precise medical history and medical examination are prerequisites for the accurate diagnosis of myositis. […] Needle EMG of affected muscles usually displays a myopathic pattern, and signs of acute damage may be noted. […] A biopsy is the most important and most invasive step to make the correct diagnosis; it is the only way to distinguish between the different subtypes of myositis.

• #1 Myositis – AmeriPharma® Specialty Care

  https://ameripharmaspecialty.com/other-health-conditions/myositis/

  Myositis Diagnosis: There are a series of different tests that can help diagnose myositis. These include: Blood Tests: Muscles contain several proteins that are continuously released into the blood as our body makes new cells and fixes damaged cells. When there is an increase in muscle cell damage, the levels of these proteins increase in the blood as well. An elevated level of muscle proteins can help diagnose myositis. The most prominent ones that are tested for in myositis are creatine kinase (CK), and aldolase. Other blood tests, such as antinuclear antibodies (ANA), check for abnormal antibodies that help identify if an autoimmune condition is present. […] Electromyography (EMG): EMG studies test the specific response of muscles to electrical nerve signals. By doing so, EMG identifies muscles that are weak or damaged by myositis.

• #1 Myositis: Diagnosis & Treatment | Allegheny Health Network

  https://www.ahn.org/services/neuroscience/conditions/neuromuscular-disorders-care/myositis

  Myositis refers to a group of rare diseases that cause muscle inflammation, resulting in muscle fatigue and weakness. At Allegheny Health Network (AHN) Neuroscience Institute, our physicians are expertly trained to diagnose and treat the many forms of myositis, including dermatomyositis and polymyositis. […] At AHN, one of our neuromuscular experts performs a thorough neurological examination. Your physician will also talk to you about your symptoms as well as your medical and family history. […] You have access to the most effective diagnostic tests available. Your physician may order one or more of these tests before providing a precise diagnosis: […] Electromyogram (EMG): This test measures the electrical activity of muscles. […] Nerve conduction studies: A nerve conduction velocity test measures the nerves ability to send electrical signals. We often perform it along with an EMG to help determine whether symptoms are related to your nerves or muscles.

• #1 Myositis: Symptoms, Causes, Diagnosis and Treatments

  https://www.webmd.com/a-to-z-guides/myositis-symptoms-treatments-prognosis

  Muscle biopsy. This is the most accurate way to diagnose myositis. During the biopsy, your doctor will identify a weak muscle, make a small incision, and remove a tiny sample of muscle tissue for testing. In most cases, a muscle biopsy leads to a clear diagnosis. […] Because many conditions can cause muscle weakness and pain, and testing for myositis isnt always a straightforward process, getting a proper diagnosis can take some time.

• #1 Myositis – Selected Immune Disorders and Disability – NCBI Bookshelf

  https://www.ncbi.nlm.nih.gov/books/NBK584479/

  A professionally accepted diagnosis is based on a combination of a patients history, clinical examination, and laboratory tests such as creatine kinase and muscle biopsy. Additional testing can include myopathic features on electromyography and the detection of myositis autoantibodies; these modalities can confirm a clinically suspected diagnosis and help clinicians evaluate the risk of systemic involvement and myositis-associated cancers. […] Muscle biopsy should be considered in the diagnosis of all adult patients with inflammatory myopathy. The histologic features of both DM and PM include muscle fiber necrosis, degeneration, regeneration, and an inflammatory cell infiltrate. DM can be distinguished from PM using muscle biopsy. In DM, cellular infiltrate is predominantly perifascicular and often perivascular. Other indicators of DM are B lymphocytes and an increased number of plasmacytoid dendritic cells. In patients with typical DM presentation, a skin biopsy or test confirming myositis-specific autoantibodies may be sufficient to confirm a diagnosis of DM.

• #1 Diagnosis – Inclusion-Body Myositis (IBM) – Diseases | Muscular Dystrophy Association

  https://www.mda.org/disease/inclusion-body-myositis/diagnosis

  Diagnosing inclusion body myositis (IBM) may require a combination of testing modalities. People with the disease may exhibit: […] Muscle biopsy is still the gold standard in diagnostic testing for IBM. A biopsy sample from a person with IBM is unique because of its inclusion bodies, for which the disease is named. These bodies (which do not appear in normal cells) contain clumps of discarded cellular material. Inflammatory cells can be seen invading muscle tissue, although some researchers believe this invasion is secondary to the primary events in the muscle tissue, presumably those that cause the inclusion bodies to appear.

• #1 Idiopathic Inflammatory Myopathies – Musculoskeletal and Connective Tissue Disorders – Merck Manual Professional Edition

  https://www.merckmanuals.com/professional/musculoskeletal-and-connective-tissue-disorders/systemic-rheumatic-diseases/idiopathic-inflammatory-myopathies

  Biopsy findings can vary, but chronic inflammation with muscle degeneration and some regeneration is typical. […] To increase the sensitivity of biopsy results, the sample should be obtained from a muscle that has 1 or more of the following characteristics: Weakness on physical examination, Muscle edema identified on MRI, Contralateral muscle shown to be abnormal on electromyography. […] Polymyositis and dermatomyositis can often be distinguished by muscle biopsy. […] Muscle biopsy is not usually necessary when skin findings are characteristic of dermatomyositis. […] Characteristic skin changes can occur in the absence of muscle disease (amyopathic dermatomyositis).

• #1 Adult Inflammatory Myopathies: Updates on Classification and Management

  https://practicalneurology.com/diseases-diagnoses/neuromuscular/adult-inflammatory-myopathies-updates-on-classification-and-management/32123/

  Diagnosing IM and its subgroups involves evaluating a combination of clinical symptoms and signs, as well as muscle biopsy features, muscle MRI patterns, serologic assessments, electroneuromyography features, and serum levels of muscle enzymes. […] In this article, we review the diagnosis, classification, and evaluation of IMs. […] Each dermatomyositis-specific autoantibody recognizes one of several different proteins or collections of proteins, including the Mi-2/nucleosome remodeling and deacetylase (NuRD) complex, NXP2, TIF1, and MDA5. […] The hallmark feature of dermatomyositis muscle biopsy is perifascicular atrophy. […] However, only ~50% of individuals with dermatomyositis have this histopathologic feature. […] Although a muscle biopsy may be helpful to confirm a diagnosis of dermatomyositis when perifascicular atrophy is present, individuals with typical skin manifestations or a known dermatomyositis-specific autoantibody usually do not require a muscle biopsy to confirm the diagnosis.

• #1 Inflammatory Myopathies | Choose the Right Test

  https://arupconsult.com/content/inflammatory-myopathies

  Laboratory testing for inflammatory myopathies is appropriate in individuals with progressive muscle weakness, particularly in patients with muscular, cutaneous, pulmonary, and articular manifestations, after more common etiologies have been ruled out. […] The European League Against Rheumatism (EULAR) and American College of Rheumatology (ACR) published updated classification criteria for inflammatory myopathies in 2017. These criteria, presented in the following table, were intended to improve on the sensitivity and specificity of the 1975 Bohan and Peter criteria, help differentiate inflammatory myopathies from conditions with similar presentations, and distinguish the primary inflammatory myopathy subtypes. […] Identification of the particular inflammatory myopathy subtype can be performed only in cases of a diagnostic probability of 55% (corresponding to a EULAR/ACR score of 5.5 without biopsy data or 6.7 with biopsy data), per the EULAR/ACR criteria.

• #1 New Tools for Myositis Diagnosis, Classification & Management – The Rheumatologist

  https://www.the-rheumatologist.org/article/new-tools-for-myositis-diagnosis-classification-management/?singlepage=1

  After a 10-year development process, the new EULAR/ACR Classification Criteria for Adult and Juvenile Idiopathic Inflammatory Myopathies and Their Major Subgroups was published in 2017. These criteria reflect updated knowledge of the myositis disease spectrum and included 976 myositis cases and 624 comparators contributed by 47 rheumatology, dermatology, neurology and pediatric clinics worldwide, said Ingrid E. Lundberg, MD, PhD, a professor in the Division of Rheumatology at Karolinska Institute, Karolinska University Hospital, Sweden. […] The new criteria score variables in a case to determine the probability a patient has one of several IIM conditions. Variables include age of first symptom onset; clinical muscle symptoms, such as weakness; skin variables, such as heliotrope rash or Gottrons papules; other clinical variables, such as dysphagia or esophageal dysmotility; laboratory variables, such as elevated serum creatine kinase (CK) and other muscle enzymes, as well as positivity for autoantibodies, such as anti-Jo-1; and muscle biopsy results. Each variable is weighted differently on the basis of whether the patient does or does not have muscle biopsy data. The criteria development committee recommended having 55% probability as a lower limit for classification, or a score of 5.5 without a muscle biopsy and 6.7 with biopsy. A patient with 90% probability is classified as a definite myositis case.

• #1

  https://journals.lww.com/ijpm/fulltext/2022/65001/current_approach_to_diagnosis_of_inflammatory.31.aspx

  In these criteria, weightage is given to symmetric involvement of the lower limb, the upper limb, neck weaknesses, and dysphagia. […] Elevated muscle enzymes also receive weightage, and so do the histopathology. […] However, electromyography (EMG) does not find position as an item. […] A current pragmatic approach to diagnosis of inflammatory myositis is delineated in figure 6. […] In a patient with classical clinical presentations such as sub-acute onset of proximal myopathy or classical DM rash or muscle biopsy features, the diagnosis is relatively straightforward.

• #1 How to diagnose Myositis? – Myositis Support and Understanding

  https://understandingmyositis.org/diagnose-myositis/

  Diagnosing Myositis can be a long and frustrating journey. It is not unusual to be seen by several doctors over months or years. Unfortunately, it is also not unusual to be misdiagnosed, thereby delaying effective treatment or being given the wrong treatment. Some reasons this may happen are: […] The criteria used to diagnosis myositis did not fully represent all inflammatory myopathies. This criteria only worked well when there was muscle involvement. […] Newly updated criteria was released in late 2017 thanks to The European League Against Rheumatism/American College of Rheumatology (EULAR/ACR). There is also an online IIM calculator that can aid use of the new criteria. […] During your journey towards a diagnosis of Myositis, you will likely visit many specialists depending on your symptoms.

• #1 Myositis – Selected Immune Disorders and Disability – NCBI Bookshelf

  https://www.ncbi.nlm.nih.gov/books/NBK584479/

  Idiopathic inflammatory myopathies (IIMs), often collectively known as myositis, are rare diseases characterized by inflammation and weakness of the skeletal muscles which can also involve internal organs such as the lungs, heart, and esophagus. In clinical practice the most common myopathies are polymyositis (PM) and dermatomyositis (DM). The currently accepted diagnostic categories are PM, DM, necrotizing autoimmune myopathy (NAM, also known as immune-mediated necrotizing myopathy, or IMNM), antisynthetase syndrome, overlap myositis, inclusion body myositis, and juvenile myositis. This chapter focuses on the more commonly known phenotypes: adult dermatomyositis, adult polymyositis, and juvenile dermatomyositis (JDM). […] DM is a rare disease with multiple organ involvement which is clinically heterogeneous and can be difficult to diagnose. DM primarily affects the skin, muscles, joints, and lungs. Skin lesions in DM play an important role in the diagnosis and can present with or prior to muscle weakness. In more than half of patients, skin lesions appear before muscle involvement by months or years. PM is also a rare, immune-mediated disease with multiple organ involvement in which muscle weakness is a predominant feature; however, there is usually no skin involvement. PM is historically considered to be a diagnosis of exclusion, defined as a subacute proximal myopathy in adults who do not have rash, family history of neuromuscular disease, exposure to myotoxic drugs, involvement of facial and extraocular muscles, endocrinopathy, or the clinical phenotype of IBM.

• #1

  https://www.healio.com/news/rheumatology/20200827/diagnosis-detective-untangling-the-web-of-myositis-and-its-mimics

  Patients with myositis typically present with telltale muscle inflammation. However, properly identifying the source of inflammation can be a challenging prospect for clinicians, especially when other diseases bear oddly similar features. […] Delays in diagnoses are common with myositis itself as well as its mimics, noting one key reason for delays or misdiagnosis. The patient usually requires evaluation by multiple specialists. This can take time, and it calls for a degree of expertise to try to tease out these fine nuances. […] Diagnosing a myositis mimic is difficult even for clinicians who are familiar with them. Delays in diagnoses are common with myositis itself as well as its mimics, noting one key reason for delays or misdiagnosis. The patient usually requires evaluation by multiple specialists. This can take time, and it calls for a degree of expertise to try to tease out these fine nuances.

• #1

  https://www.healio.com/news/rheumatology/20200827/diagnosis-detective-untangling-the-web-of-myositis-and-its-mimics

  Clinicians should carefully examine the patient history for clues that show deviations from established myositis symptoms. […] Lastly, clinicians should always be concerned when patients are not responding to therapy. Whenever that happens, reconsidering the diagnosis is a valuable place to start. […] While myositis and their mimics can present a number of diagnostic pitfalls, the workup should be similar to the approach for any rheumatology patient. […] If further evaluation warrants, an electromyogram with nerve conduction can be done. […] While Fernandez believes that biopsy is not perfectly sensitive, it can show evidence of many causes of muscle dysfunction. […] Genetic testing may also come into play. […] During workup, a second opinion from a trusted neurology colleague can be valuable.

• #1 Myositis – Selected Immune Disorders and Disability – NCBI Bookshelf

  https://www.ncbi.nlm.nih.gov/books/NBK584479/

  Autoantibodies found in patients with myositis are classified into myositis-specific antibodies (MSAs) and myositis-associated antibodies (MAAs). MSAs are detected in between 30 percent and 50 percent of patients with DM, although in some larger specialty centers the percentage of DM patients with autoantibodies can be as high as 80 percent. DM-specific autoantibodies are rarely found in other diseases, and usually a patient only has one specific MSA, so the presence of a DM-specific autoantibody can confirm a diagnosis of DM in an adult patient. Identifying particular MSAs can help clinicians predict disease course, for example by providing information about the risk of systemic effects and cancer. […] The usual course of myositis is progressive, but it can be relapsing and remitting with periods of worsening and quiescence. The disease course can be categorized as monophasic, meaning a disease in which the patient can eventually be tapered off medication; chronic, meaning the patient continues to require medication; or polyphasic, meaning that the patient experiences relapse and remission. The disease course and outcomes vary, and prognosis depends on systemic effects and multimorbidity. […] Prompt diagnosis and treatment generally leads to better outcomes, decreased permanent damage, and decreased long-term disability.

• #1 Diagnosis and management of inflammatory muscle disease

  https://www.hcplive.com/view/diagnosis-and-management-inflammatory-muscle-disease

  Electromyography is most useful for distinguishing between neuropathic and myopathic disease. […] Muscle histology can help identify the specific type of idiopathic inflammatory myopathy; however, histological changes may be minimal or nonspecific. […] In polymyositis, muscle fibers are seen in various stages of necrosis and regeneration. […] Inflammation in dermatomyositis is predominantly perivascular and consists of CD4+ helper T cells, plasmacytoid dendritic cells, and B lymphocytes. […] The histopathology of inclusion body myositis may be identical to that seen in polymyositis. […] Dermatomyositis has a higher association with malignancies than polymyositis or inclusion body myositis. […] A CT scan of the chest, abdomen, and pelvis and a thorough screening for age-appropriate cancer are recommended at the time of diagnosis.

• #1 Inflammatory Myopathies | Choose the Right Test

  https://arupconsult.com/content/inflammatory-myopathies

  Inflammatory myopathies (also referred to collectively as myositis) are a heterogeneous group of chronic autoimmune disorders characterized by inflammation of muscles and diverse clinical manifestations, with variable risk for organ involvement and cancer and variable response to treatment. […] Accurate diagnosis is critical for appropriate treatment, to determine prognosis, and to prevent complications, but can be challenging because of the possible multisystem involvement as well as the varied and overlapping presentations among subtypes. Diagnosis involves clinical examination (particularly of patterns of muscle weakness), evaluation of the muscles using imaging and electromyography, laboratory tests for specific autoantibodies, and often, histologic analysis of biopsied muscle tissue. Identification of specific autoantibodies can help to determine the disease subtype.

• #1 Diagnosis of Myositis | Tests, Symptoms & Early Detection | Myositis India

  https://www.myositisindia.org/diagnosis-of-myositis

  Initial diagnosis is based on history and physical examination of the patient by an experienced doctor who have specific knowledge about myositis. […] The physician takes these observations into consideration when making a preliminary diagnosis. […] After making a preliminary diagnosis, the next step is to find supporting evidence. […] Elevated CK levels in the blood can indicate a problem with the muscle, and is an important piece of evidence in myositis diagnosis. […] The Electromyogram (EMG) test is a crucial tool for diagnosis of myositis. […] The use of magnetic resonance imaging (MRI) scans has become a common tool for diagnosing muscle disease, including myositis. […] A biopsy of muscle and/or skin tissue is often needed for a definitive diagnosis. […] A muscle biopsy provides the most reliable evidence for the physician to make a confident diagnosis and determine the proper treatment.

• #1 Myositis: Muscle Inflammation | Inflammatory Myopathy | HSS

  https://www.hss.edu/condition-list_myositis.asp

  Myositis can be hard to diagnose, but comprehensive assessment using all the tools available can make this possible. […] A diagnosis is made by taking the patients history, conducting a physical exam, and performing diagnostic tests, including. […] Patients with myositis usually complain of muscle weakness, particularly in the proximal muscle groups like the deltoids in the arms and the quadriceps in the upper legs. […] Diagnostic blood tests will usually show high levels of muscle enzymes in the circulation, which is a sign of muscle breakdown and damage. […] A muscle biopsy is the gold standard to diagnosis myositis. […] This can be difficult, as both types of myositis can look like other diseases. […] There is no cure for myositis, but most patients can manage their symptoms.

• #1 Diagnosis of Myositis | Tests, Symptoms & Early Detection | Myositis India

  https://www.myositisindia.org/diagnosis-of-myositis

  To further aid in the diagnosis of myositis, patients can undergo testing for myositis-specific autoantibodies (MSAs) and myositis-associated autoantibodies (MAAs). […] Their presence can also provide information on the potential course of the disease and its treatment. […] Elevated CK levels in the blood can signal muscle damage from either a chronic condition or an acute injury. […] In myositis, CK levels are often greatly elevated beyond normal range. […] The physician will make the most accurate diagnosis based on all available information, including physical examination, blood tests, EMG, MRI scans, and the biopsy results.

• #1 Diagnosis and management of inflammatory muscle disease

  https://www.hcplive.com/view/diagnosis-and-management-inflammatory-muscle-disease

  Because the idiopathic inflammatory myopathies are relatively rare, referral to a specialist who is familiar with these diseases is recommended. […] Generally, the earlier in the disease course medical therapy is started, the more effective and rapid improvement in symptoms it produces. […] Ninety percent of patients who have polymyositis or dermatomyositis and are treated with corticosteroids achieve some clinical response; 50% to 75% achieve complete remission. […] Prednisone should provide objective improvement in muscle weakness within 3 to 6 months. […] A recent systematic review highlighted the lack of quality studies assessing the efficacy and toxicity of various immunosuppressants in dermatomyositis and polymyositis. […] However, no medication has been found that alters the course of inclusion body myositis.

• #1 Inclusion Body Myositis – Diagnosis | Cure IBM

  https://cureibm.org/diagnosis/introduction/

  Electromyography (EMG) and nerve conduction studies measure electrical activity in the arms and legs and can help determine if the disease is primarily affecting the muscles or the nerves, or both, in a pattern typically seen in IBM. […] Magnetic Resonance Imaging (MRI) can show edema (swelling), atrophy (muscle wasting), and replacement of muscle tissue by fat. […] Muscle biopsy is the best available test for diagnosing inclusion body myositis. […] Misdiagnosis is common, but can usually be avoided if attention is paid to key findings. […] The European Neuromuscular Centre (ENMC) has recently developed new guidelines for the diagnosis of inclusion body myositis. […] The doctors who are most expert at diagnosing inclusion body myositis are generally neurologists who specialize in neuromuscular diseases like Parkinson’s disease, multiple sclerosis, and amyotrophic lateral sclerosis (ALS). […] Inclusion body myositis didn’t have an ICD code until several years ago.

• #2 Myositis Diagnosis & Treatment | Mount Sinai – New York

  https://www.mountsinai.org/care/rheumatology/services/myositis

  Myositis is an inflammatory condition that affects the muscles. […] The diagnosis of myositis involves a complete physical exam, blood test, electromyography (a neurological test that assess the electrical activity in your muscles), and a muscle biopsy, which involves removing a small sample of muscle tissue for testing. […] Mount Sinai rheumatologists have extensive experience in diagnosing and treating autoimmune myositis.

• #2

  https://www.healio.com/news/rheumatology/20200827/diagnosis-detective-untangling-the-web-of-myositis-and-its-mimics

  Patients with myositis typically present with telltale muscle inflammation. However, properly identifying the source of inflammation can be a challenging prospect for clinicians, especially when other diseases bear oddly similar features. […] Delays in diagnoses are common with myositis itself as well as its mimics, noting one key reason for delays or misdiagnosis. The patient usually requires evaluation by multiple specialists. This can take time, and it calls for a degree of expertise to try to tease out these fine nuances. […] Diagnosing a myositis mimic is difficult even for clinicians who are familiar with them. Delays in diagnoses are common with myositis itself as well as its mimics, noting one key reason for delays or misdiagnosis. The patient usually requires evaluation by multiple specialists. This can take time, and it calls for a degree of expertise to try to tease out these fine nuances.

• #2 How to diagnose Myositis? – Myositis Support and Understanding

  https://understandingmyositis.org/diagnose-myositis/

  An office visit with a physician will likely include asking about a patients medical history and that of their family members. Some doctors feel that a patients medical and family history is one of the most important parts of helping to diagnose an illness, especially a complicated one like Myositis. […] In addition to a clinical examination and discussion of existing symptoms and history, physicians often conduct many diagnostic tests to assist in narrowing down a diagnosis. Tests include markers for autoimmunity, inflammation, and autoantibodies. […] Many patients with Myositis have elevated levels of muscle enzymes which may indicate the presence of muscle damage. […] It is estimated that around 50% of myositis patients have myositis-specific and/or myositis-associated antibodies.

• #2 Idiopathic Inflammatory Myopathies – Musculoskeletal and Connective Tissue Disorders – Merck Manual Professional Edition

  https://www.merckmanuals.com/professional/musculoskeletal-and-connective-tissue-disorders/systemic-rheumatic-diseases/idiopathic-inflammatory-myopathies

  The diagnosis of inflammatory myopathies requires a detailed clinical history and physical examination in addition to laboratory studies, electromyography, MRI, and, if available, histologic evaluation. […] Laboratory studies can increase or decrease suspicion for inflammatory myopathies, assess organ involvement and its severity, and help identify overlap syndromes. […] Muscle enzymes, which include creatinine kinase (CK), aldolase, and aminotransferases, may be elevated. CK is considered the most specific test; aldolase and aminotransferases are also present in hepatocytes. […] Myositis-specific and sometimes myositis-associated autoantibodies should be tested, some of which are available as a panel. […] Electromyography (EMG) with or without magnetic resonance imaging (MRI) of the affected muscles (eg, thighs) should be considered in patients with muscle weakness and elevated muscle enzymes.

• #2 Myositis: Laboratory Support for Classification and Diagnosis | Clinical Focus | Quest Diagnostics Myositis: Laboratory Support for Classification and DiagnosisMyositis: Laboratory Support for Classification and Diagnosis

  https://testdirectory.questdiagnostics.com/test/test-guides/CF_Myositis/myositis-laboratory-support-for-classification-and-diagnosis

  Quest Diagnostics offers tests and panels that may be useful for classifying or diagnosing myositis. […] On initial evaluation, about 80% to 90% of myositis patients have elevated creatine kinase (CK) associated with muscle damage. Using elevated CK to diagnose IIMs has limitations, however. CK levels may be only slightly elevated, or normal, due to lack of muscle mass or the presence of circulating CK inhibitors or CK antibodies. Normal CK levels may also be observed in patients with IBM, as well as those with juvenile or amyopathic dermatomyositis. Another limitation is that CK and other muscle enzymes are not specific markers of polymyositis/dermatomyositis. Serum elevations may be due to other types of muscle disease (muscular dystrophies, rhabdomyolysis), hypothyroidism, cardiac, or liver disease. Consequently, tests employing antibody markers, rather than muscle enzymes, are used to specifically diagnose and classify IIMs.

• #2 Making the Diagnosis of Myositis: Laboratory Testing in Myositis | SpringerLink

  https://link.springer.com/chapter/10.1007/978-3-030-15820-0_17

  Five muscle enzymes can be elevated during idiopathic inflammatory myopathies (IIM): CK, aldolase, LDH, AST, and ALT. CK level is the best marker of muscle injury but can be elevated in any eccentric exercise or at normal level in active dermatomyositis or inclusion body myositis. It is then recommended in the workup of myositis patients to evaluate these five enzymes and follow up the one more elevated for disease activity. […] The detection of autoantibodies on Hep-2 cells against nuclear and/or cytoplasmic antigens (so-called anti-nuclear antibodies (ANA)) is the initial test for the laboratory diagnosis of IIM. Nevertheless, ANA are frequently at low titer (1/160) or only showing a cytoplasmic fluorescence. In the case of a negative ANA and a strong suspicion for myositis, testing for specific or associated myositis antibodies is strongly recommended.

• #2 New Tools for Myositis Diagnosis, Classification & Management – The Rheumatologist

  https://www.the-rheumatologist.org/article/new-tools-for-myositis-diagnosis-classification-management/?singlepage=1

  A normal CK does not exclude myositis. Ingrid E. Lundberg, MD, PhD […] Diagnostic workup for a patient with possible myositis includes both clinical observation of specific skin rashes and muscle weakness, she said. […] In typical cases, you have signs of myopathy, but also have elevation of muscle enzymes. But a normal CK does not exclude myositis, said Dr. Lundberg. An EMG [electromyography] and muscle biopsy may be helpful, where you can see signs of inflammation, degeneration, necrosis and regeneration of muscle fibers. […] Additional tests, such as immune staining for MHC, magnetic resonance imaging (MRI) to look for edema or to help guide biopsy, EMG, muscle enzyme tests and testing for myositis-specific autoantibodies are helpful for diagnosis, as well as pulmonary function tests if patients also present with lung symptoms, she said. […] For diagnosis, you still need to use your clinical evaluation, autoantibodies, MRI and muscle biopsy, and all are helpful depending on the different subtypes of myositis and different organ manifestations.

• #2 Myositis Autoantibodies – Myositis Support and Understanding

  https://understandingmyositis.org/myositis-antibody-testing/

  A diagnosis of one of the Idiopathic Inflammatory Myopathies (IIM), or Myositis, can be made through various methods including clinical and physical exam, thorough patient history, blood work, EMG, MRI, and often, a muscle or skin biopsy. […] When IIM is part of the differential diagnosis, Myositis-Specific Antibodies (MSA) should also be a part of the testing. […] An estimated 50% of patients with Polymyositis or Dermatomyositis have one of the known Myositis-Specific Antibodies. […] Myositis-Specific Antibodies (MSA) have also improved our understanding of myositis by leading to the identification of certain clinical patterns. […] MSAs can assist your doctor in helping to confirm a diagnosis of certain types of Myositis such as Polymyositis and Dermatomyositis. […] It is estimated that 50% of patients with Polymyositis or Dermatomyositis have Myositis-Specific Antibodies (MSA), so when a clinical exam and other testing suggest the possibility of Myositis, the presence of these antibodies can be supporting evidence for a diagnosis.

• #2 Myositis: Laboratory Support for Classification and Diagnosis | Clinical Focus | Quest Diagnostics Myositis: Laboratory Support for Classification and DiagnosisMyositis: Laboratory Support for Classification and Diagnosis

  https://testdirectory.questdiagnostics.com/test/test-guides/CF_Myositis/myositis-laboratory-support-for-classification-and-diagnosis

  Myositis-specific antibodies for IBM and IMNM have been more recently described: cN-1A antibodies target cytosolic 5′-nucleotidase and have been reported to be highly predictive for IBM with high specificity (87%-100%) but wide ranging sensitivity estimates (33%-76%). HMGCR antibodies target 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR); positive results correctly identify nearly 100% of patients with IMNM. However, sensitivity for IMNM is about 45%. […] Myositis-associated antibodies, Ku, PM/Scl, Sjögren’s antibody [SS-A], and Smith [Sm]/U1-RNP antibody, are less specific for polymyositis and dermatomyositis and are found in 1% to 13% of these patients. A positive test result for a myositis-associated antibody in a symptomatic patient suggests the presence of either polymyositis, dermatomyositis (with rash), IMNM, or IBM; overlap myositis is also a possibility.

• #2 Myositis Autoantibodies – Myositis Support and Understanding

  https://understandingmyositis.org/myositis-antibody-testing/

  These antibodies also offer some insight into potential complications you may experience during the course of your disease and potential treatment options that may work best. […] There are now two autoantibodies found to be associated with IMNM, sometimes called Necrotizing Autoimmune Myopathy (NAM). […] This autoantibody is positive in about one-half of IBM patients. A negative test does not mean a patient does not have IBM, however, a positive test makes it likely that Inclusion Body Myositis is the correct diagnosis.

• #2 Myositis | Radiology Reference Article | Radiopaedia.org

  https://radiopaedia.org/articles/myositis-2?lang=us

  Myositis (plural: myositides) is the subset of myopathy characterized by inflammation of skeletal muscle. […] MRI is the gold standard modality for non-invasive evaluation of myositis, which shows a classic edema signal pattern (high T2WI and STIR signal) in affected muscles. Inflamed muscles demonstrate contrast enhancement. […] If chronic, T1WI will show high muscle signal indicating fat replacement and atrophy.

• #2 Myositis: Diagnosis & Treatment | Allegheny Health Network

  https://www.ahn.org/services/neuroscience/conditions/neuromuscular-disorders-care/myositis

  Magnetic resonance imaging (MRI): This imaging scan produces detailed images of internal organs and structures. Physicians may use this test to look for other causes of your symptoms. […] Blood tests: Blood tests check for abnormal thyroid hormone levels, liver damage, or other problems. […] Muscle biopsy: We remove a tiny piece of muscle for further analysis in a laboratory. […] Lumbar puncture: This test, also called a spinal tap, evaluates the cerebrospinal fluid surrounding your brain and spinal cord. We insert a needle into your lumbar area (small of your back) to remove a fluid sample.

• #2 Diagnosis of Myositis | Tests, Symptoms & Early Detection | Myositis India

  https://www.myositisindia.org/diagnosis-of-myositis

  Initial diagnosis is based on history and physical examination of the patient by an experienced doctor who have specific knowledge about myositis. […] The physician takes these observations into consideration when making a preliminary diagnosis. […] After making a preliminary diagnosis, the next step is to find supporting evidence. […] Elevated CK levels in the blood can indicate a problem with the muscle, and is an important piece of evidence in myositis diagnosis. […] The Electromyogram (EMG) test is a crucial tool for diagnosis of myositis. […] The use of magnetic resonance imaging (MRI) scans has become a common tool for diagnosing muscle disease, including myositis. […] A biopsy of muscle and/or skin tissue is often needed for a definitive diagnosis. […] A muscle biopsy provides the most reliable evidence for the physician to make a confident diagnosis and determine the proper treatment.

• #2 Polymyositis – Diagnosis and treatment – Mayo Clinic

  https://www.mayoclinic.org/diseases-conditions/polymyositis/diagnosis-treatment/drc-20353212

  If your doctor suspects you have polymyositis, he or she might suggest some of the following tests: […] A blood test will let your doctor know if you have elevated levels of muscle enzymes, which can indicate muscle damage. A blood test can also detect specific autoantibodies associated with different symptoms of polymyositis, which can help in determining the best medication and treatment. […] This test involves inserting a thin needle electrode through the skin into the muscle. Electrical activity is measured as you relax or tighten the muscle, and changes in the pattern of electrical activity can confirm a muscle disease. The doctor can determine the distribution of the disease by testing different muscles. […] A scanner creates cross-sectional images of your muscles from data generated by a powerful magnetic field and radio waves. Unlike a muscle biopsy, an MRI can assess inflammation over a large area of muscle.

• #2 Diagnosis and management of inflammatory muscle disease

  https://www.hcplive.com/view/diagnosis-and-management-inflammatory-muscle-disease

  The third step is to elicit any associated symptoms. […] The physician should assess all muscle groups, noting that the weakness in most idiopathic inflammatory myopathies is proximal (shoulder, neck, and pelvic girdle muscle) and symmetrical. […] Although serum elevations of aldolase, aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase can be seen in myopathic disease, elevation of the creatine kinase (CK) level is thought to be the most sensitive laboratory test result related to skeletal muscle damage. […] Although elevated CK levels are seen in most cases of inflammatory myopathy, CK levels may be minimally elevated or even normal in inclusion body myositis, myositis associated with neoplasia, and early presentations of polymyositis and dermatomyositis and when significant muscle atrophy has developed.

• #2 Diagnosing Inflammatory Myopathies | NYU Langone Health

  https://nyulangone.org/conditions/inflammatory-myopathies/diagnosis

  In this outpatient procedure, a doctor numbs the area to be tested with a local anesthetic and surgically removes a small piece of muscle. This is examined under a microscope for signs of chronic inflammation or muscle fiber death, which may signal an inflammatory disease. […] Testing of the body’s nerve function can help confirm a diagnosis and determine the best treatment for you. Electromyography shows how the nerves and muscles work together by measuring the electrical impulses along nerves, nerve roots, and muscular tissue. […] In people with inflammatory myopathy, the muscle fibers do not respond as well to repeated electrical stimulation as do normally functioning muscles.

• #2 RHEUM Symptoms-Myositis | Department of Medicine

  https://dom.pitt.edu/rheum/centers-institutes/myositiscenter/symptoms/

  The hallmark feature of myositis is muscle weakness with an onset that is often insidious. Patients complain of proximal weakness with difficulty holding their arms above their head or getting up from a chair or walking up steps. […] Myositis can be difficult to diagnose and there are many mimics of the IIM including drug-induced myopathy, thyroid problems, various neurologic conditions or even forms of muscular dystrophy. Tests that are helpful in making the diagnosis of myositis include: […] Muscle Biopsy: This is often considered the gold standard in patients with myositis and is essential in most cases of PM due to the many mimics of this subset of IIM. However, it is also frequently performed in DM as the skin rash may be subtle and it always helps to make a definitive diagnosis of myositis to confirm the clinical suspicion.

• #2 Muscle Biopsy testing for Myositis – Johns Hopkins Myositis Center

  https://www.hopkinsmyositis.org/unique/diagnosis-myositis/tests/muscle-biopsy-testing-myositis/

  Muscle biopsies are usually required to confirm a diagnosis of myositis. […] Biopsies performed at the Johns Hopkins Myositis Center are interpreted by experienced muscle pathologists at the Johns Hopkins Neuromuscular Pathology Lab. Your doctors will receive copies of your muscle biopsy report, usually within two weeks of the procedure. They will contact you as soon as the results are available.

• #2 Diagnosis and management of inflammatory muscle disease

  https://www.hcplive.com/view/diagnosis-and-management-inflammatory-muscle-disease

  Electromyography is most useful for distinguishing between neuropathic and myopathic disease. […] Muscle histology can help identify the specific type of idiopathic inflammatory myopathy; however, histological changes may be minimal or nonspecific. […] In polymyositis, muscle fibers are seen in various stages of necrosis and regeneration. […] Inflammation in dermatomyositis is predominantly perivascular and consists of CD4+ helper T cells, plasmacytoid dendritic cells, and B lymphocytes. […] The histopathology of inclusion body myositis may be identical to that seen in polymyositis. […] Dermatomyositis has a higher association with malignancies than polymyositis or inclusion body myositis. […] A CT scan of the chest, abdomen, and pelvis and a thorough screening for age-appropriate cancer are recommended at the time of diagnosis.

• #2 Adult Inflammatory Myopathies: Updates on Classification and Management

  https://practicalneurology.com/diseases-diagnoses/neuromuscular/adult-inflammatory-myopathies-updates-on-classification-and-management/32123/

  Diagnosing IM and its subgroups involves evaluating a combination of clinical symptoms and signs, as well as muscle biopsy features, muscle MRI patterns, serologic assessments, electroneuromyography features, and serum levels of muscle enzymes. […] In this article, we review the diagnosis, classification, and evaluation of IMs. […] Each dermatomyositis-specific autoantibody recognizes one of several different proteins or collections of proteins, including the Mi-2/nucleosome remodeling and deacetylase (NuRD) complex, NXP2, TIF1, and MDA5. […] The hallmark feature of dermatomyositis muscle biopsy is perifascicular atrophy. […] However, only ~50% of individuals with dermatomyositis have this histopathologic feature. […] Although a muscle biopsy may be helpful to confirm a diagnosis of dermatomyositis when perifascicular atrophy is present, individuals with typical skin manifestations or a known dermatomyositis-specific autoantibody usually do not require a muscle biopsy to confirm the diagnosis.

• #2 Myositis – Selected Immune Disorders and Disability – NCBI Bookshelf

  https://www.ncbi.nlm.nih.gov/books/NBK584479/

  A professionally accepted diagnosis is based on a combination of a patients history, clinical examination, and laboratory tests such as creatine kinase and muscle biopsy. Additional testing can include myopathic features on electromyography and the detection of myositis autoantibodies; these modalities can confirm a clinically suspected diagnosis and help clinicians evaluate the risk of systemic involvement and myositis-associated cancers. […] Muscle biopsy should be considered in the diagnosis of all adult patients with inflammatory myopathy. The histologic features of both DM and PM include muscle fiber necrosis, degeneration, regeneration, and an inflammatory cell infiltrate. DM can be distinguished from PM using muscle biopsy. In DM, cellular infiltrate is predominantly perifascicular and often perivascular. Other indicators of DM are B lymphocytes and an increased number of plasmacytoid dendritic cells. In patients with typical DM presentation, a skin biopsy or test confirming myositis-specific autoantibodies may be sufficient to confirm a diagnosis of DM.

• #2 New Tools for Myositis Diagnosis, Classification & Management – The Rheumatologist

  https://www.the-rheumatologist.org/article/new-tools-for-myositis-diagnosis-classification-management/?singlepage=1

  After a 10-year development process, the new EULAR/ACR Classification Criteria for Adult and Juvenile Idiopathic Inflammatory Myopathies and Their Major Subgroups was published in 2017. These criteria reflect updated knowledge of the myositis disease spectrum and included 976 myositis cases and 624 comparators contributed by 47 rheumatology, dermatology, neurology and pediatric clinics worldwide, said Ingrid E. Lundberg, MD, PhD, a professor in the Division of Rheumatology at Karolinska Institute, Karolinska University Hospital, Sweden. […] The new criteria score variables in a case to determine the probability a patient has one of several IIM conditions. Variables include age of first symptom onset; clinical muscle symptoms, such as weakness; skin variables, such as heliotrope rash or Gottrons papules; other clinical variables, such as dysphagia or esophageal dysmotility; laboratory variables, such as elevated serum creatine kinase (CK) and other muscle enzymes, as well as positivity for autoantibodies, such as anti-Jo-1; and muscle biopsy results. Each variable is weighted differently on the basis of whether the patient does or does not have muscle biopsy data. The criteria development committee recommended having 55% probability as a lower limit for classification, or a score of 5.5 without a muscle biopsy and 6.7 with biopsy. A patient with 90% probability is classified as a definite myositis case.

• #2

  https://journals.lww.com/ijpm/fulltext/2022/65001/current_approach_to_diagnosis_of_inflammatory.31.aspx

  Diagnosis of inflammatory myositis has been made easier with the availability of commercial assays for myositis-specific and myositis-associated antibodies. […] Overall, the muscle-specific and myositis-associated antibodies have changed the landscape in terms of diagnostic utility, prognostication, and the approach to organ-specific evaluation and management of idiopathic inflammatory myopathies (IIMs). […] Currently, clinicians use EULAR/ACR classification criteria for diagnosis of IIM, which is a robust validated and weighted score. […] A web-based calculator can be used to derive the diagnosis and further classify patients into polymyositis (PM), IBM, ADM, DM, or juvenile dermatomyositis (JDM). […] Using this classification, a score of 7.5 (8.7 with muscle biopsy) is categorized as 'definite IIM’.

• #2 For Health Professionals – Myositis Association Australia

  https://myositis.org.au/myositis/for-health-professionals/

  With the current average time to diagnosis of five years, GPs and other health professionals play a critical role in diagnosing this rare and progressive muscle disease. The earlier a patient is diagnosed, the better their potential health outcomes will be. […] Detailed information for diagnosing and treating Myositis is available in this Physicians Guide to Inflammatory Myopathies. […] Medical Practitioners are encouraged to order a MYOSITIS PANEL BLOOD TEST. Researchers continue to identify particular autoantibodies as biomarkers for Myositis diseases. These autoantibodies are rarely found in other diseases, so their presence in the patients blood can confirm the diagnosis of: Dermatomyositis, Polymyositis, Immune-Mediated Necrotizing Myopathies, Inclusion Body Myositis. […] The EULAR/ACR classification criteria for idiopathic inflammatory myopathies (IIM) were developed in 2017. […] As part of this international collaboration, a web-based calculator was developed to estimate the probability of myositis diagnosis and subtype.

• #2 Myositis: Laboratory Support for Classification and Diagnosis | Clinical Focus | Quest Diagnostics Myositis: Laboratory Support for Classification and DiagnosisMyositis: Laboratory Support for Classification and Diagnosis

  https://testdirectory.questdiagnostics.com/test/test-guides/CF_Myositis/myositis-laboratory-support-for-classification-and-diagnosis

  Myositis: Laboratory Support for Classification and Diagnosis […] This Clinical Focus provides an overview of the use of laboratory testing to classify and diagnose myositis caused by the idiopathic inflammatory myopathies. […] The differential diagnosis of IIMs and overlap myositis begins with the exclusion of muscular dystrophy and myopathies of known cause (eg, infectious, metabolic, drug-induced, or neurologic). Diagnosis is aided by imaging, electromyography, biopsy, testing levels of muscle enzymes in serum, and the detection of myositis-specific and myositis-associated antibodies. In addition, the detection of certain antibodies may have prognostic value. […] Individuals suitable for testing […] Individuals with symptoms of IIM (eg, unexplained muscle weakness, rash, evidence of systemic disease)

• #2

  https://www.healio.com/news/rheumatology/20200827/diagnosis-detective-untangling-the-web-of-myositis-and-its-mimics

  Clinicians should carefully examine the patient history for clues that show deviations from established myositis symptoms. […] Lastly, clinicians should always be concerned when patients are not responding to therapy. Whenever that happens, reconsidering the diagnosis is a valuable place to start. […] While myositis and their mimics can present a number of diagnostic pitfalls, the workup should be similar to the approach for any rheumatology patient. […] If further evaluation warrants, an electromyogram with nerve conduction can be done. […] While Fernandez believes that biopsy is not perfectly sensitive, it can show evidence of many causes of muscle dysfunction. […] Genetic testing may also come into play. […] During workup, a second opinion from a trusted neurology colleague can be valuable.

• #2 How to diagnose Myositis? – Myositis Support and Understanding

  https://understandingmyositis.org/diagnose-myositis/

  A muscle biopsy is performed to assess the musculoskeletal system for abnormalities. […] The muscle biopsy is considered the gold standard in diagnosing myositis and can rule out other diseases. […] A positive skin sample can confirm the diagnosis of Dermatomyositis and rule out other disorders, such as Lupus. […] An MRI gives a cross-section image of muscles in a specific area to show if inflammation exists. […] Because of a high cancer risk found in some forms of Myositis, both before and after diagnosis, doctors will often perform cancer screenings at the onset or suspicion of Myositis. […] The International Myositis Classification Criteria Project (IMCCP), after many years of hard work, and composed of a large number of prominent myositis physicians and researchers across the globe, developed these evidence-based criteria for both adult and juvenile forms of myositis.

• #2 Diagnosis of Myositis | Tests, Symptoms & Early Detection | Myositis India

  https://www.myositisindia.org/diagnosis-of-myositis

  To further aid in the diagnosis of myositis, patients can undergo testing for myositis-specific autoantibodies (MSAs) and myositis-associated autoantibodies (MAAs). […] Their presence can also provide information on the potential course of the disease and its treatment. […] Elevated CK levels in the blood can signal muscle damage from either a chronic condition or an acute injury. […] In myositis, CK levels are often greatly elevated beyond normal range. […] The physician will make the most accurate diagnosis based on all available information, including physical examination, blood tests, EMG, MRI scans, and the biopsy results.

• #2 Adult Inflammatory Myopathies: Updates on Classification and Management

  https://practicalneurology.com/diseases-diagnoses/neuromuscular/adult-inflammatory-myopathies-updates-on-classification-and-management/32123/

  The inflammatory myopathies are classified into homogeneous subtypes on the basis of specific autoantibodies, and management strategies continue to evolve rapidly. Adult Inflammatory Myopathies Updates on Classification and Management Restart Program Play Program Media formats available: […] Inflammatory myopathies (IM), commonly referred to as myositis, constitute a group of rare autoimmune diseases mostly affecting skeletal muscle. […] The classification of IM comprises dermatomyositis, overlap myositis, antisynthetase syndrome (ASyS), immune-mediated necrotizing myopathy (IMNM), and sporadic inclusion body myositis (sIBM). […] The diagnosis of polymyositis is controversial and should only be made when the other types of myositis have been excluded. […] The identification of myositis-specific autoantibodies, which are present in up to 60% of individuals with IM, and myositis-associated autoantibodies has been linked to specific clinical phenotypes, and can be used to classify individuals with IMs into homogeneous phenotypic subtypes.

• #3 Myositis: Symptoms, Causes & Treatment

  https://my.clevelandclinic.org/health/diseases/24170-myositis

  Myositis is a disease that makes your immune system attack your muscles. […] A healthcare provider will diagnose a type of myositis based on your symptoms and the location of your affected muscles. […] A healthcare provider will diagnose myositis with a physical exam and tests. […] Theres no cure for myositis. Your provider will treat your symptoms to reduce their impact on your daily routine. […] Theres no cure for myositis, but in most cases, treatment can put it into remission. […] Some cases of myositis can be fatal. Around 5% of people with dermatomyositis die within a year of their diagnosis. […] Myositis is chronic muscle inflammation caused by your immune system attacking muscles throughout your body.

• #3 Diagnostic delay of myositis: an integrated systematic review | Orphanet Journal of Rare Diseases | Full Text

  https://ojrd.biomedcentral.com/articles/10.1186/s13023-022-02570-9

  Due to the low prevalence of IIM, range of clinical features, lack of comprehensive and internationally accepted diagnostic criteria, diagnosis of IIM can be challenging and many patients experience significant diagnostic delays. […] The mean diagnostic delay in IIM ranged from 3.48 to 96.0 months. […] The pooled overall mean diagnostic delay was 27.91 months (95% CI 15.0340.79, I2=99%). […] Subgroup analyses revealed significant differences in mean diagnostic delay between different IIM subtypes. Compared to other IIM subtypes JDM had the shortest mean delay (6.73 months, 95% CI=10.4023.85) whereas IBM had the longest mean delay (61.95 months, 95% CI=47.6676.24). […] We found longer diagnostic delay in gatekeeper health systems when compared with non-gatekeeper health systems, indicating that the difference in accessibility to specialists influences time to diagnosis.

• #3 RHEUM Symptoms-Myositis | Department of Medicine

  https://dom.pitt.edu/rheum/centers-institutes/myositiscenter/symptoms/

  The hallmark feature of myositis is muscle weakness with an onset that is often insidious. Patients complain of proximal weakness with difficulty holding their arms above their head or getting up from a chair or walking up steps. […] Myositis can be difficult to diagnose and there are many mimics of the IIM including drug-induced myopathy, thyroid problems, various neurologic conditions or even forms of muscular dystrophy. Tests that are helpful in making the diagnosis of myositis include: […] Muscle Biopsy: This is often considered the gold standard in patients with myositis and is essential in most cases of PM due to the many mimics of this subset of IIM. However, it is also frequently performed in DM as the skin rash may be subtle and it always helps to make a definitive diagnosis of myositis to confirm the clinical suspicion.

• #3 Making the Diagnosis of Myositis: Laboratory Testing in Myositis | SpringerLink

  https://link.springer.com/chapter/10.1007/978-3-030-15820-0_17

  Five muscle enzymes can be elevated during idiopathic inflammatory myopathies (IIM): CK, aldolase, LDH, AST, and ALT. CK level is the best marker of muscle injury but can be elevated in any eccentric exercise or at normal level in active dermatomyositis or inclusion body myositis. It is then recommended in the workup of myositis patients to evaluate these five enzymes and follow up the one more elevated for disease activity. […] The detection of autoantibodies on Hep-2 cells against nuclear and/or cytoplasmic antigens (so-called anti-nuclear antibodies (ANA)) is the initial test for the laboratory diagnosis of IIM. Nevertheless, ANA are frequently at low titer (1/160) or only showing a cytoplasmic fluorescence. In the case of a negative ANA and a strong suspicion for myositis, testing for specific or associated myositis antibodies is strongly recommended.

• #3 Inclusion Body Myositis – Diagnosis | Cure IBM

  https://cureibm.org/diagnosis/introduction/

  Inclusion Body Myositis – Diagnosis […] The typical patient with inclusion body myositis does not receive an accurate diagnosis for at least several years after symptoms begin. […] Although the diagnosis of inclusion body myositis is often difficult and complicated, an experienced doctor can frequently make a tentative diagnosis by simply listening to the patient’s story and performing a physical examination. […] Symptoms include a long, gradual history of slowly worsening muscle weakness, often demonstrated by frequent falls, difficulty standing up from a chair, and decreasing hand grip strength. […] Physical Examination reveals weakness which is often greatest in certain typical areas, such as the fingers and the thighs. […] Blood tests include serum creatine kinase and an anti-cN1A (NT5C1A) antibody test.

• #3 Dermatomyositis – Diagnosis & treatment – Mayo Clinic

  https://www.mayoclinic.org/diseases-conditions/dermatomyositis/diagnosis-treatment/drc-20353192

  If your doctor suspects that you have dermatomyositis, he or she might suggest some of the following tests: […] A blood test will let your doctor know if you have elevated levels of muscle enzymes that can indicate muscle damage. A blood test can also detect autoantibodies associated with different symptoms of dermatomyositis, which can help in determining the best medication and treatment. […] A doctor with specialized training inserts a thin needle electrode through the skin into the muscle to be tested. Electrical activity is measured as you relax or tighten the muscle, and changes in the pattern of electrical activity can confirm a muscle disease. The doctor can determine which muscles are affected. […] A small piece of skin or muscle is removed for laboratory analysis. A skin sample can help confirm the diagnosis of dermatomyositis. A muscle biopsy might reveal inflammation in your muscles or other problems, such as damage or infection. If the skin biopsy confirms the diagnosis, a muscle biopsy might not be necessary. […] For dermatomyositis, questions to ask your doctor include: What tests might I need? Are special preparations required? […] Your doctor will likely ask you questions, such as: What, if anything, seems to improve your symptoms?

• #3 Inclusion body myositis: A differential diagnosis to consider in patients with myopathy refractory to immunosuppressants. Two case reports | Revista Colombiana de Reumatología (English Edition)

  https://www.elsevier.es/en-revista-revista-colombiana-reumatologia-english-edition–474-articulo-inclusion-body-myositis-a-differential-S2444440521000601

  The first accepted clinical criteria were those proposed by Griggs in 1995; later, the European Neuromuscular Centre in 2011 defined some criteria to classify the disease into 2 categories: clinical-pathological IBM and clinical IBM. […] The optimal treatment of IBM is currently unknown and most of the interventions have had limited benefits, for which the use of immunosuppressive therapy is compulsory, with an unfavorable prognosis when compared with other inflammatory myopathies. […] The diagnosis of inclusion body myositis can be difficult, since the clinical presentation has a slow evolution and in the first years it can be nonspecific. Given the foregoing, a high index of suspicion is required, as well as a comprehensive association of the clinical history, the levels of muscle enzymes and complementary studies such as biopsy and electromyography.

• #4 Diagnosis and management of inflammatory muscle disease

  https://www.hcplive.com/view/diagnosis-and-management-inflammatory-muscle-disease

  The diagnosis of an idiopathic inflammatory myopathy is made by finding a combination of a typical clinical presentation in association with elevated levels of enzymes of muscle origin, myopathic changes on electromyography, edema in muscle on MRI, and characteristic muscle histopathology. […] No single feature is diagnostic of an idiopathic inflammatory myopathy, and the diagnosis can be made only after the exclusion of other causes of these abnormalities. […] Muscle weakness is the chief complaint in patients with any of the idiopathic inflammatory myopathies. […] The first step in diagnosing an idiopathic inflammatory myopathy is to determine the time course of the weakness. […] The second step is to determine the characteristics of the weakness and the effect it has on daily life.

• #4 Adult Inflammatory Myopathies: Updates on Classification and Management

  https://practicalneurology.com/diseases-diagnoses/neuromuscular/adult-inflammatory-myopathies-updates-on-classification-and-management/32123/

  Autoantibodies recognizing HMGCR are associated with IMNM and statin use. […] AntiHMGCR antibodypositive myopathy accounts for approximately 6% of all idiopathic IMs and 40% of all IMNMs. […] Individuals develop subacute or insidious proximal muscle weakness, markedly elevated CK levels, irritative myopathy on EMG, and muscle edema on MRI. […] Compared with HMGCR-IMNM and antibody-negative IMNM, SRP-IMNM has a lower risk of underlying malignancy. […] Five primary types of IMs are recognized: dermatomyositis, including amyopathic dermatomyositis; overlap myositis; ASyS; IMNM; and sIBM. […] Within each type, specific autoantibodies separate cases into homogeneous subtypes.

• #4 Making the Diagnosis of Myositis: Muscle Biopsy and Interpretation | SpringerLink

  https://link.springer.com/chapter/10.1007/978-3-030-15820-0_13

  Histopathologic examination of skeletal muscle is an important component of the evaluation of a patient with suspected myopathy, especially inflammatory myopathy. Proper biopsy site selection is important and can be guided by clinical examination and ancillary testing. The history should be provided to the pathologist who then processes the specimen for frozen sections at minimum. There is a variety of histochemical and immunohistochemical staining that can be performed. Characteristic findings are seen in most of the inflammatory myopathies. […] The histopathology in autoimmune necrotizing myopathy is nonspecific myofiber degeneration and regeneration with no or subtle lymphocytic inflammation in most cases. The histopathology of anti-synthetase syndrome, even in patients without a rash, is similar to dermatomyositis.

• #5 Diagnosis of Myositis – Johns Hopkins Myositis Center

  https://www.hopkinsmyositis.org/unique/diagnosis-myositis/

  Diagnosis of myositis will be made by our team of doctors, after reviewing your testing results and evaluating you at the Myositis Center. […] In order to make a definite diagnosis of myositis, the following criteria must be met: […] Patients should exhibit at least one of the following: […] Weakness of the shoulder and/or hip muscles. […] In cases of dermamyositis, particular skin findings are significant. Usually a patchy, reddish rash on the knuckles, or eyelids are indicative of dermatomyositis when coupled with other significant symptoms like muscle weakness. […] Elevated muscle enzymes […] Electromyography must be consistent with feature of an inflammatory myopathy […] Muscle biopsy demonstrates changes consistent with inflammation. […] Your doctors may also recommend the following tests to determine if you have myositis: […] Electromyography (EMG) and nerve conduction studies (NCS) […] MRI of the muscles […] Muscle Biopsy […] Pulmonary Function Tests.

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