General or Other | Rheumatology | Polymyositis (Disease)


Polymyositis is an idiopathic inflammatory myopathy that causes symmetrical, proximal muscle weakness; elevated skeletal muscle enzyme levels; and characteristic electromyography (EMG) and muscle biopsy findings.

Causes and Risk factors

The etiology of polymyositis is unknown and may be multifactorial, perhaps related to autoimmune factors, genetics, and viruses. In rare cases, the cause is known to be infectious, associated with the pathogens that cause Lyme disease, toxoplasmosis, and other infectious agents.

The incidence of polymyositis increases with age, with the highest rates being seen in the 35-44 and 55-64 year old age groups. Women are two times more likely to suffer from polymyositis than men.

Polymyositis usually is considered non-fatal in the absence of ILD. It is hypothesized that an initial injury causes release of muscle auto antigen, which is subsequently taken up by macrophages and presented to CD4+ TH cells.

Diagnosis and Treatment

The first line treatment for polymyositis is corticosteroids. A course of high dose prednisone, tapered according to response will often bring about a dramatic improvement. It is also useful to distinguish from inclusion body myositis.

Unresponsive patients may be tried on other immunosuppressive medications. IVIG (intravenous immunoglobulin) has also shown to be a beneficial treatment. Specialized exercise therapy may supplement treatment to enhance quality of life. ...