Polymyositis (adult)

Definition:

A systemic connective tissue disease, which is characterized by inflammation and degeneration of the muscles.

Causes, incidence, and risk factors:

The cause of this disorder is unknown. It is thought 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 those between 50 to 70 years old, or in children between 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, or climbing stairs. The voice may be affected by weakness of the larynx. Joint pain, inflammation of the heart, and pulmonary (lung) disease may occur. A similar condition, called dermatomyositis, is evident when a dusky, red rash appears over the face, neck, shoulders, upper chest, and back. A malignancy may be associated with this disorder. The incidence of polymyositis is 5 out of 10,000 people.