What Are Myopathies?

Autoimmune myopathies are a group of diseases that involve inflammation of the muscles and may be associated with diseases of internal organs. Diseases affecting muscles include polymyositis, dermatomyositis and inclusion body myositis. 

The main symptom is muscle weakness in the upper arms, upper legs and neck, muscle pain, fatigue, joint pain and swelling, rashes over the face and knuckles, fevers, swallowing difficulty and shortness of breath.

Woman demonstrating sore areas along the shoulders in reference to myopathies



The cause of myopathies is unknown, but environmental factors (such as viral infections) and genetic predisposition are felt to be important in some cases.



Diagnosis is attained through a history and physical exam, certain laboratory tests, muscle biopsy and electromyography (a study of the electrical activity of muscle). Other diseases or conditions such as hypothyroidism, toxin exposure, drug reactions and genetic disorders may also affect muscles and need to be ruled out.

Health Impact


  • Only about 1 new case per 100,000 is diagnosed each year.
  • Myopathies occur two to three times more frequently in women than men.
  • Severity of disease varies from a mild form with almost no symptoms to a severe, life-threatening disease.
young woman gripping her shoulder in discomfort



These complex diseases can involve many body organs and, while not curable, many of the symptoms can be treated effectively with patient education, physical and occupational therapy, and medications. Medications may include corticosteroids and immunosuppressive drugs (drugs that keep the immune system from attacking its own body), such as methotrexate and azathioprine.

The Rheumatologist’s Role in Treating Myopathies

Rheumatologists specialize in the diagnosis and treatment of myopathies. Researchers play a critical role in both basic science and clinical investigation of the disease. Rheumatologists educate other physicians about the disease and its treatment.