autoimmune disease of musculoskeletal system systemic autoimmune disease acquired skeletal muscle disease idiopathic inflammatory myopathy An umbrella term for diseases which have chronic muscle inflammation and weakness of unknown etiology. The types of idiopathic inflammatory myopathy are further defined by either clinicopathologic criteria or by the presence of certain autoantibodies. GARD:0009128 ICD9:359.79 IIm IMM MONDO:0020122 NCIT:C116796 Orphanet:98482 SCTID:702380008 UMLS:C0751356 idiopathic inflammatory myopathies idiopathic inflammatory myopathy, familial idiopathic inflammatory myositis