RT Book, Section A1 Mammen, Andrew L. A1 Truong, Alex A1 Christopher-Stine, Lisa A2 Imboden, John B. A2 Hellmann, David B. A2 Stone, John H. SR Print(0) ID 57272818 T1 Chapter 27. Dermatomyositis, Polymyositis, & Immune-Mediated Necrotizing Myopathy T2 CURRENT Diagnosis & Treatment: Rheumatology, 3e YR 2013 FD 2013 PB The McGraw-Hill Companies PP New York, NY SN 978-0-07-163805-0 LK accessmedicine.mhmedical.com/content.aspx?aid=57272818 RD 2024/03/29 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).MRI of affected muscles reveals evidence of edema or fasciitis or both.A heliotrope rash, Gottron sign/papules are pathognomonic for dermatomyositis.Muscle biopsy findings frequently reveal endomysial, perimysial, and perivascular lymphocytic infiltrates. Except for perifascicular atrophy, which is pathognomonic for dermatomyositis, muscle biopsy findings are variable and nonspecific.A careful family history, medication list review, physical examination, laboratory evaluation, and muscle biopsy are critical and help exclude an alternative diagnosis, such as an inherited muscle disease or toxic myopathy.