Cutaneous Manifestations of Dermatomyositis : a Comprehensive Review

Dermatomyositis (DM) is an idiopathic inflammatory myopathy characterized by the presence of skin lesions and inflammation of skeletal muscles; however, this feature may be absent in amyopathic DM. DM is a rare disease, occurring at any age, and has two peaks of incidence: one in childhood between 5 and 15 years of age and one in adulthood between 40 and 60 years, with a female preponderance. DM has been associated with malignancy; therefore, every newly diagnosed patient should undergo screening investigations, but evidence-based guidelines on their extension are lacking. The etiopathogenesis is still unclear, but a range of factors such as genetic predisposition, environment triggers, and immune- and non-immune-mediated mechanisms play a role in the development of the disorder. Some dermatological findings and new discoveries on immunological mechanisms in DM, including the association of certain autoantibodies with cancer, can be helpful in clinical practice. Therapy should consider both skin and muscle or internal organ involvement. Photoprotection, including the use of antimalarial drugs, plays an important role in the therapeutic approach of skin involvement. Treatment of muscle and internal organ involvement is based on systemic corticosteroids, alone or in association with disease-modifying antirheumatic drugs. Intravenous immunoglobulins have been demonstrated to be effective as second-line therapy. Rituximab is an emerging treatment for difficult-to-treat DM, both in adults and children. In this review article, we discuss DM subforms, focusing on their dermatological manifestations that can be classified as pathognomonic, characteristic, compatible, less common, rare, recently-described, and non-specific skin lesions.