What is Polymyositis (PM)?

Polymyositis is an inflammatory disease that causes muscles to become irritated and inflamed, eventually causing breakdown or weakness. It can affect muscles all over the body, impairing the ability to run, walk, or lift objects, as well as the muscles used for eating and breathing.


While rare in general, polymyositis is most common among adults ages 30-60 with signs and symptoms usually developing gradually, over weeks or months. The muscles closest to the center of the body (proximal muscles) tend to be those affected most.

The common symptoms include:

  • Muscle pain and stiffness
  • Muscle weakness, particularly in the abdomen, shoulders, upper arms, and hips
  • Joint pain and stiffness
  • Shortness of breath
  • Problems swallowing
  • Irregular heart rhythms (if the heart muscle becomes inflamed)


While there is no cure for polymyositis, treatment — ranging from medications to physical therapy — can improve muscle strength and function. The earlier treatment is started in the course of the disease, the more effective it is with fewer complications. Treatment type and variety will depend on the symptoms, age, and general health of the patient.

Treatments include:

  • Anti-inflammatory medicines: Steroid drugs or corticosteroids that ease inflammation in the body generally provide relief within 4-6 weeks.
  • Immunosuppressive drugs: Medications that block or slow down the body’s immune system.
  • Physical therapy:Special exercises help to stretch and strengthen the muscles.
  • Heat therapy and rest:Used to help lessen muscle symptoms.
  • Braces or other special devices:To help support muscles and aid movement.