[Myositis and the skin: cutaneous manifestations of dermatomyositis]

Idiopathic inflammatory myopathies include dermatomyositis, polymyositis, and inclusion body myositis. Among them, cutaneous manifestations are observed most frequently in dermatomyositis. While dermatomyositis commonly affects the skin and muscles, it can also affect the lungs and other organs. Dermatomyositis presenting clinically and histopathologically with typical cutaneous lesions, but without myositis, is called amyopathic dermatomyositis. Given that the Bohan and Peter criteria cannot distinguish amyopathic dermatomyositis, understanding the characteristic skin manifestations may be essential for diagnosing this condition. The cutaneous manifestations of dermatomyositis are thought to be the result of the Koebner phenomenon, vasculopathy, or photosensitivity; manifestations include various eruptions, such as heliotrope rush, Gottron's sign, Gottron's papules, mechanic's hand, nail-fold bleeding, skin ulcer, vasculitis, flagellate erythema, V-sign, and Shawl sign. The presence of multiple types of eruptions can help diagnose the disease. Several skin diseases, including adult Still's disease, contact dermatitis, and sarcoidosis, can mimic the cutaneous manifestations of dermatomyositis. Skin biopsy is useful for differential diagnoses. Histopathologically, dermatomyositis of the skin is characterized by liquefaction degeneration, vacuolar degeneration, edema, and mucin deposition. Dermatologists, neurologists, and rheumatologists are responsible for the diagnosis and management of dermatomyositis, in cooperation with pulmonologists, pediatricians, and pathologists. This review aims to provide clinicians with recent findings regarding skin involvement in dermatomyositis.