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What is polymyositis?

Polymyositis is a rare disease of the connective tissues that causes skeletal muscles to weaken. Polymyositis is characterized by muscle weakness and inflammation. Polymyositis can develop at any time, but African Americans, women, and adults between 30 and 50 are most susceptible.

Donna Hill Howes, RN
Family Medicine

Polymyositis is one of a group of muscle diseases known as 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 the age of 18; most cases are in adults between the ages of 31 and 60. Progressive muscle weakness starts in the proximal muscle (the muscle closest to the trunk of the body), which eventually leads to difficulty climbing stairs, rising from a sitting position, lifting objects, or reaching overhead. People with polymyositis may also experience arthritis, shortness of breath, difficulty swallowing and speaking, and heart arrhythmias. In some cases of polymyositis, distal muscles (muscles further away from the trunk of the body, such as those in the forearms and around the ankles and wrists) may be affected as the disease progresses. Polymyositis may be associated with collagen-vascular or autoimmune diseases, such as lupus. Polymyositis may also be associated with infectious disorders, such as human immunodeficiency virus/acquired immune deficiency (HIV/AIDS).

This answer from the National Institute of Neurological Disorders and Stroke has been reviewed and/or edited by Dr. William D. Knopf.

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