Dermatomyositis

Definition:

A connective-tissue disease that is characterized by inflammation and degeneration of the muscles throughout the body (systemic) and the skin.

Causes, incidence, and risk factors:

The cause of this disorder is unknown. It is theorized that an autoimmune reaction or a viral infection of the skeletal muscle may cause the disease. It can affect people at any age, but most commonly occurs in people fifty to sixty years old or in children from 5 to 15 years old. It affects women twice as often as men. Muscle weakness may appear suddenly or occur slowly over weeks or months. There may be difficulty with raising the arms over the head, rising from a sitting position, and climbing stairs. A dusky, red rash may appear over the face, neck, shoulders, upper chest, and back. Joint pain, inflammation of the heart, and lung (pulmonary) disease may occur. A malignancy may rarely be associated with this disorder. A similar condition is called polymyositis when the symptoms occur without any skin manifestations. The incidence of dermatomyositis is 5 out of 10,000 people.