Dermatomyositis

In immunology, dermatomyositis is an autoimmune disease and a connective tissue disease that is "a subacute or chronic inflammatory disease of muscle and skin, marked by proximal muscle weakness and a characteristic skin rash. The illness occurs with approximately equal frequency in children and adults. The skin lesions usually take the form of a purplish rash (or less often an exfoliative dermatitis) involving the nose, cheeks, forehead, upper trunk, and arms. The disease is associated with a complement mediated intramuscular microangiopathy, leading to loss of capillaries, muscle ischemia, muscle-fiber necrosis, and perifascicular atrophy. The childhood form of this disease tends to evolve into a systemic vasculitis. Dermatomyositis may occur in association with malignant neoplasms."

Dermatomyositis may be a part of the antisynthetase syndrome.

Diagnosis
Dermatomyositis may be associated with autoantibodies to histidine-tRNA ligase (anti-synthetase - most commonly Jo-1 antibody) which acetylates transfer RNA (tRNA).