Vascular changes and perifascicular muscle fiber damage in dermatomyositis: another question of the chicken or the egg that is on our mind

Dermatomyositis (DM) is a multisystem disease with symptoms spanning diverse body functions including the skin, the joints, the heart and the lungs. The skin manifestations involve a sun-sensitive rash on the face, neck and upper trunk, and erythema of knees, elbows and knuckles. In classical cases, where these typical skin manifestations combine with muscle weakness, diagnosis can be set on clinical grounds. In other cases, diagnosis is confirmed by assessing the level of serum muscle enzymes, electromyographic findings, and a muscle biopsy (1). In the skeletal muscle tissue of DM, the primary target of the immune response is the vascular endothelium of perimysial and perifascicular blood vessels, and inflammatory infiltrates often occur at perivascular sites. Complement deposition of the terminal C5b-9 membrane attack complex (MAC) leads to blood vessel necrosis (2). The trigger that initiates complement activation remains however unclear.