Polymyositis

Polymyositis tends to become evident in adulthood, presenting with bilateral proximal muscle weakness, often noted in the upper legs due to early fatigue while walking. The weakness is generally progressive, accompanied by lymphocytic inflammation (mainly cytotoxic T8 lymphocytes). The cause is unknown, but seems to be related to autoimmune factors, genetics, and perhaps viruses. In rare cases, the cause is known to be infectious, associated with the pathogens that cause Lyme disease, Toxoplasmosis, and others.

Polymyositis, like Dermatomyositis, strikes females with greater frequency than males. The skin involvement of Dermatomyositis is absent in Polymyositis.

Diagnosis is fourfold, including elevation of creatine kinase, signs and symptoms, electromyograph (EMG) alteration, and a positive muscle biopsy. Treatment generally involves glucocorticoids, esp. prednisone.

N.B.: This article is not meant as a substitution for consultation with a qualified physician.

REFERENCES

• Kasper DL, Braunwald E, Fauci AS, Hauser SL, Longo DL, Jameson JL. Harrison's Principles of Internal Medicine. New York: McGraw-Hill, 2005. ISBN 0071391401