The diagnosis of dermatomyositis (DM) can be problematic. Serum levels of muscle enzymes are not elevated in every case, electromyography (EMG) presents with sampling errors and even findings of muscle biopsy specimens may be normal due to patchy muscle involvement. Moreover, the classic muscle findings are not present in all patients—the term amyopathic DM has been used to describe patients diagnosed as having DM with skin disease and no muscle findings.1 Particularly difficult is the detection of steroid myopathy in the follow-up of patients with DM. A muscle biopsy is not always helpful since type II atrophy and patches of inflammation may coexist.2,3
Yosipovitch G, Beniaminov O, Rousso I, David M. STIR Magnetic Resonance Imaging: A Noninvasive Method for Detection and Follow-up of Dermatomyositis. Arch Dermatol. 1999;135(6):721–723. doi:10-1001/pubs.Arch Dermatol.-ISSN-0003-987x-135-6-dlt0699
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