How common are polymyositis and dermatomyositis?
• They affect 15,000 (1 in 2,000) . • Women are affected by polymyositis and dermatomyositis twice as often as men. • These diseases occur most often in children between the ages of 5 and 15 and in adults between the ages of 50 and 70. Polymyositis and dermatomyositis can occur at any age but are most common in children and adults over age 50. More adults than children get these diseases. One to five new cases per 100,000 are seen each year. Women are affected by polymyositis and dermatomyositis twice as often as men.
