Type of disease: Rare conditions
Polymyositis is one of a group of muscle diseases known as the inflammatory myopathies, which are characterized by chronic muscle inflammation accompanied by muscle weakness. Polymyositis affects skeletal muscles (those involved with making movement) on both sides of the body. It is rarely seen in persons under age 18; most cases are seen in adults between the ages of 31 and 60. The cause of polymyositis is not fully understood. Although there’s no cure for polymyositis, treatment can improve muscle strength and function. Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.