Anti-MDA5 dermatomyositis mimicking psoriatic arthritis

Dermatomyositis causes inflammation and damage of muscle and skin, and sometimes involves internal organs, especially lung parenchyma. Patients with dermatomyositis still represent a diagnostic challenge because of the rarity of this disease and the lack of specificity of some of its cutaneous manifestations. Herein, we describe the case of a patient with dermatomyositis, initially diagnosed as psoriatic arthritis, in which the performance of anti-melanoma differentiation-associated gene 5 (MDA5) antibodies was decisive to establish a definitive diagnosis.