TY - CHAP M1 - Book, Section TI - Autoimmune Myopathies, Immune-Mediated Necrotizing Myopathies, & Their Mimickers A1 - Adler, Brittany A1 - Truong, Alex A1 - Mammen, Andrew L. A1 - Christopher-Stine, Lisa A2 - Stone, John H. PY - 2021 T2 - Current Diagnosis & Treatment: Rheumatology, 4e AB - Symmetric proximal muscle weakness progressing over weeks to months.Elevated muscle enzymes, including creatine kinase (CK), aldolase, aspartate aminotransferase (AST), and alanine aminotransferase (ALT).An “irritable myopathy” shown by electromyography (EMG).Magnetic resonance imaging (MRI) of affected muscles reveals evidence of edema, fasciitis, or both.Heliotrope rash or Gottron sign/papules are pathognomonic of dermatomyositis.Muscle biopsy in dermatomyositis and polymyositis frequently reveals endomysial, perimysial, and perivascular lymphocytic infiltrates. Perifascicular atrophy is pathognomonic of dermatomyositis.Muscle biopsy with necrotizing and regenerating muscle fibers is characteristic of the immune-mediated necrotizing myopathies, including statin-associated autoimmune myopathy.A careful family history, medication list review, physical examination, laboratory evaluation, and muscle biopsy are all critical parts of the evaluation.Exclusion of alternative diagnoses, such as an inherited muscle disease or toxic myopathy, is essential. SN - PB - McGraw Hill CY - New York, NY Y2 - 2024/04/16 UR - accessmedicine.mhmedical.com/content.aspx?aid=1180197069 ER -