Cutaneous manifestations in myositis syndromes

Idiopathic inflammatory myopathies (IIM) are a heterogeneous group of autoimmune diseases with variable extramuscular involvement of the skin, lungs, and other organ systems. Dermatomyositis (DM) is the prototype IIM with skin involvement, but the presence of DM-specific rashes in other IIMs raises questions about whether these conditions are distinct entities, overlapping diseases, or subsets within a DM spectrum. Importantly, distinct cutaneous phenotypes of IIMs may correlate with certain autoantibodies and risk of malignancy or interstitial lung disease. In this review, we outline characteristic DM rashes and describe their prevalence in other IIMs, most notably in antisynthetase syndrome and overlap myositis. We emphasize salient skin findings that may inform diagnosis and prognosis, including some atypical, subtle, or unusual presentations. Finally, we review established and emerging therapies for management of amyopathic or refractory cutaneous DM.