{"id":2346,"date":"2015-05-13T14:40:25","date_gmt":"2015-05-13T14:40:25","guid":{"rendered":"https:\/\/medicalcriteria.com\/web\/reuim\/"},"modified":"2026-03-25T19:09:15","modified_gmt":"2026-03-25T19:09:15","slug":"reuim","status":"publish","type":"post","link":"https:\/\/medicalcriteria.com\/web\/reuim\/","title":{"rendered":"Diagnosis of Inflammatory Myopathies"},"content":{"rendered":"<div class=\"99c380e4b4a7b96c35d7ddf7dcb434e8\" data-index=\"1\" style=\"float: none; margin:0px 0 0px 0; text-align:center;\">\n<script async src=\"https:\/\/pagead2.googlesyndication.com\/pagead\/js\/adsbygoogle.js\"><\/script>\r\n<!-- MC 2019- Horizontal -->\r\n<ins class=\"adsbygoogle\"\r\n     style=\"display:block\"\r\n     data-ad-client=\"ca-pub-0127150553352455\"\r\n     data-ad-slot=\"3806776041\"\r\n     data-ad-format=\"auto\"\r\n     data-full-width-responsive=\"true\"><\/ins>\r\n<script>\r\n     (adsbygoogle = window.adsbygoogle || []).push({});\r\n<\/script>\n<\/div>\n<p>The diagnosis of the exact subtype of inflammatory myopathy is based on the combination of clinical history, tempo of disease progression, pattern of muscle involvement, muscle enzyme levels, electromyographic findings, muscle-biopsy analysis, and for some conditions, the presence of certain autoantibodies.<br \/>\n<!--more--><br \/>\n<b>Criteria Supporting the Diagnosis of Inflammatory Myopathies<\/b><\/p>\n<table style=\"border-collapse: collapse; width: 100%;\" border=\"1\">\n<tbody>\n<tr valign=\"TOP\">\n<td width=\"20%\"><b>Criterion<\/b><\/td>\n<td width=\"20%\"><b>Dermatomyositis<\/b><\/td>\n<td width=\"20%\"><b>Polymyositis<\/b><\/td>\n<td width=\"20%\"><b>Necrotizing Autoimmune Myositis<\/b><\/td>\n<td width=\"20%\"><b>Inclusion-Body Myositis<\/b><\/td>\n<\/tr>\n<tr valign=\"TOP\">\n<td width=\"20%\">Pattern of muscle weakness<\/td>\n<td width=\"20%\">Subacute onset of proximal symmetric weakness with characteristic skin rash in patients of any age<\/td>\n<td width=\"20%\">Subacute onset of proximal symmetric\u00a0weakness in adults (diagnosis is\u00a0made when other causes have been\u00a0ruled out)*<\/td>\n<td width=\"20%\">Acute or subacute onset of proximal,\u00a0often severe weakness in\u00a0adults<\/td>\n<td width=\"20%\">Slow onset of proximal and distal weakness;\u00a0atrophy of quadriceps and\u00a0forearms; frequent falls; mild facial\u00a0muscle weakness in people older\u00a0than 50 years of age<\/td>\n<\/tr>\n<tr valign=\"TOP\">\n<td width=\"20%\">Creatine kinase level<\/td>\n<td width=\"20%\">High, up to 50 times the upper limit of normal; can at times be normal<\/td>\n<td width=\"20%\">High, up to 50 times the upper limit of\u00a0normal in early active disease; may\u00a0linger at up to 10 times the upper\u00a0limit of normal<\/td>\n<td width=\"20%\">Very high; more than 50 times the\u00a0upper limit of normal in early\u00a0active disease<\/td>\n<td width=\"20%\">Up to 10 times the upper limit of normal;\u00a0can be normal or slightly\u00a0elevated<\/td>\n<\/tr>\n<tr valign=\"TOP\">\n<td width=\"20%\">Electro- myography<\/td>\n<td width=\"20%\">Myopathic units (active and chronic)<\/td>\n<td width=\"20%\">Myopathic units (active and chronic)<\/td>\n<td width=\"20%\">Active myopathic units<\/td>\n<td width=\"20%\">Myopathic units (active and chronic)\u00a0with some mixed large-size potentials<\/td>\n<\/tr>\n<tr valign=\"TOP\">\n<td width=\"20%\">Muscle biopsy<\/td>\n<td width=\"20%\">Perivascular, perimysial, and perifascicular inflammation; necrotic fibers in \u201cwedge-like\u201d infarcts; perifascicular atrophy; reduced capillaries\u2020<\/td>\n<td width=\"20%\">CD8+ cells invading healthy fibers; widespread\u00a0expression of MHC class I\u00a0antigen; no vacuoles; ruling out of\u00a0inflammatory dystrophies<\/td>\n<td width=\"20%\">Scattered necrotic fibers with macrophages; no CD8+ cells or vacuoles; deposits of complement on capillaries\u2021<\/td>\n<td width=\"20%\">CD8+ cells invading healthy fibers; widespread expression of MHC class I antigen; autophagic vacuoles, \u00a7 ragged-red or ragged-blue fibers; congophilic amyloid deposits\u00b6<\/td>\n<\/tr>\n<tr valign=\"TOP\">\n<td width=\"20%\">Autoantibodies<\/td>\n<td width=\"20%\">Autoantibodies Anti-MDA-5, anti-Mi-2; anti-TIF-1 and anti-NXP-2 (implicated in cancer- associated dermatomyositis)<\/td>\n<td width=\"20%\">Antisynthetase antibodies (often seen in\u00a0overlap myositis) associated with interstitial\u00a0lung disease, arthritis,\u00a0fever, and \u201cmechanic\u2019s hands\u201d<\/td>\n<td width=\"20%\">Anti-SRP and anti-HMGCR, specific\u00a0for necrotizing autoimmune\u00a0myositis<\/td>\n<td width=\"20%\">Anti-cN1A (of uncertain pathologic significance)<\/td>\n<\/tr>\n<tr valign=\"TOP\">\n<td width=\"20%\">Magnetic resonance imaging<\/td>\n<td width=\"20%\">May show active inflammation<\/td>\n<td width=\"20%\">May show active inflammation; could\u00a0guide biopsy site<\/td>\n<td width=\"20%\">May show active inflammation;\u00a0could guide biopsy site<\/td>\n<td width=\"20%\">Shows selective muscle involvement,\u00a0but might be difficult to distinguish\u00a0atrophy from chronic inflammation<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>* Drug-induced myopathies (e.g., penicillamine, statins, or antiretrovirals), inflammatory dystrophies (such as those due to mutations in the genes encoding dysferlin, calpain, or anoctamin;\u00a0Becker\u2019s muscular dystrophy; facioscapulohumeral muscular dystrophy; or myofibrillar myopathies), inclusion-body myositis, necrotizing autoimmune myositis, metabolic myopathies,\u00a0and fasciitis or fibromyalgia need to be ruled out.<br \/>\n\u2020 Similar pathologic changes in the perifascicular, perimysial, and interfascicular areas (to a lesser degree of severity) can be seen in overlap myositis (without skin lesions) or the antisynthetase\u00a0syndrome.<br \/>\n\u2021 Metabolic muscle diseases presenting as myoglobinuria and toxic or drug-induced myopathies need to be ruled out.<br \/>\n\u00a7 In clinical inclusion-body myositis, when patients have the typical inclusion-body myositis phenotype, vacuoles are absent; such patients are erroneously thought to have polymyositis\u00a0because of polymyositis-like inflammation; ragged-red fibers or cytochrome oxidase\u2013negative fibers are frequently present and are helpful in diagnosis.<br \/>\n\u00b6TDP43 and p62 deposits, detected with the use of immunostaining, have been proposed as tissue biomarkers.<\/p>\n<p>Abbreviations:<\/p>\n<ul>\n<li>MHC: Major histocompatibility complex<\/li>\n<li>anti-MDA-5:\u00a0Anti\u2013melanoma differentiation\u2013associated protein-5<\/li>\n<li>Anti-Mi-2: Autoantibody directed against a nuclear DNA helicase involved in transcriptional activation<\/li>\n<li>Anti-TIF-1:\u00a0Anti\u2013transcriptional intermediary factor 1<\/li>\n<li>Anti-NXP-2: Anti\u2013nuclear matrix protein 2<\/li>\n<li>Anti-SRP:\u00a0Anti\u2013signal recognition particle<\/li>\n<li>Anti-HMGCR:\u00a0Anti\u20133-hydroxy-3-methylglutaryl\u2013coenzyme A reductase<\/li>\n<li>Anti-cN1A, or anti-NT5C1A:\u00a0Anti\u2013cytosolic 5-nucleotidase 1A<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<p><b>References:<\/b><\/p>\n<ol>\n<li>Dalakas MC. Inflammatory muscle diseases.\u00a0N Engl J Med. 2015 Apr 30;372(18):1734-47.\u00a0<a href=\"https:\/\/pubmed.ncbi.nlm.nih.gov\/25923553\/\" target=\"_blank\" rel=\"noopener noreferrer\">[Medline]<\/a><\/li>\n<li>Dalakas MC. Inflammatory muscle diseases: a critical review on pathogenesis and therapies.\u00a0Curr Opin Pharmacol. 2010 Jun;10(3):346-52.\u00a0<a href=\"https:\/\/pubmed.ncbi.nlm.nih.gov\/20409756\/\" target=\"_blank\" rel=\"noopener noreferrer\">[Medline]<\/a><\/li>\n<li>Wischnewski S, Rausch HW, Ikenaga C, Leipe J, Lloyd TE, Schirmer L. Emerging mechanisms and therapeutics in inflammatory muscle diseases. Trends Pharmacol Sci. 2025 Mar;46(3):249-263. <a href=\"https:\/\/pubmed.ncbi.nlm.nih.gov\/39939222\/\" target=\"_blank\" rel=\"noopener\">[Medline]<\/a><\/li>\n<\/ol>\n<div><\/div>\n<div><\/div>\n<div>Created May 13, 2015.<br \/>\nUp-date Mar 25, 2026.<\/div>\n<p><\/p>\n\n<div style=\"font-size: 0px; height: 0px; line-height: 0px; margin: 0; padding: 0; clear: both;\"><\/div>","protected":false},"excerpt":{"rendered":"<p>Sorry, this entry is only available in Espa\u00f1ol.<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_lmt_disableupdate":"no","_lmt_disable":"no","_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"footnotes":""},"categories":[45],"tags":[16,15,123,13,809,810,811],"class_list":["post-2346","post","type-post","status-publish","format-standard","hentry","category-rheumatology","tag-criteria","tag-criterios","tag-diagnosis","tag-diagnostico","tag-inflammatory","tag-miopatias","tag-myopathies"],"modified_by":"Guillermo Firman","_links":{"self":[{"href":"https:\/\/medicalcriteria.com\/web\/wp-json\/wp\/v2\/posts\/2346","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/medicalcriteria.com\/web\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/medicalcriteria.com\/web\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/medicalcriteria.com\/web\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/medicalcriteria.com\/web\/wp-json\/wp\/v2\/comments?post=2346"}],"version-history":[{"count":4,"href":"https:\/\/medicalcriteria.com\/web\/wp-json\/wp\/v2\/posts\/2346\/revisions"}],"predecessor-version":[{"id":10726,"href":"https:\/\/medicalcriteria.com\/web\/wp-json\/wp\/v2\/posts\/2346\/revisions\/10726"}],"wp:attachment":[{"href":"https:\/\/medicalcriteria.com\/web\/wp-json\/wp\/v2\/media?parent=2346"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/medicalcriteria.com\/web\/wp-json\/wp\/v2\/categories?post=2346"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/medicalcriteria.com\/web\/wp-json\/wp\/v2\/tags?post=2346"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}