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What is Polymyositis / Dermatomyositis?

Polymyositis and dermatomyositis affect individuals of all ages, but mostly those between 15-44 years of age. The annual incidence of polymyositis and dermatomyositis ranges from 5–10 new cases per million. The average female-to-male ratio exceeds 2:1, with women predominating in this disease.

The idiopathic inflammatory myopathies are immune-mediated processes, believed to be triggered by environmental factors in genetically susceptible individuals. The specific causes or triggering events remain unknown, but viruses have been strongly implicated.

How Are Polymyositis and
Dermatomyositis Diagnosed?

The criteria for the diagnosis of polymyositis and dermatomyositis include:


  • Symmetrical weakness
  • Muscle biopsy evidence
  • Elevation of muscle enzymes
  • Electromyographic evidence
  • Dermatologic features


  • Usually progressive, of the limb-girdle muscles
  • Necrosis of type I and II muscle fibers; phagocytosis; degeneration and regeneration of myofibers with variation in myofiber size; endomysial, perimysial, perivascular or interstitial mononuclear cells
  • Specifically, creatine phosphokinase, aldolase, lactate dehydrogenase, transaminases (ALT and AST)
  • Short, small, low-amplitude polyphasic motor unit potentials; fibrillation potentials, and bizarre high-frequency repetitive changes
  • Heliotrope rash (lilac discoloration of the eyelids and periorbital area), Gottron’s papules (scaly erythematous eruptions over the metacarpophalangeal and interphalangeal joints or over other extensor surfaces), Gottron’s sign (erythema in the area of Gottron’s papules but without papules

How Are These Diseases Treated?

Polymyositis is usually first treated with high doses of corticosteroids — cortisone medications such as prednisone and prednisolone which are given by mouth or intravenously. They can help decrease the inflammation in the muscles. Immunosuppressive medications are considered when corticosteroids do not adequately improve the condition. These medications (Methotrexate, Rheumatrex, Trexall, Azathioprine can be effective in suppressing the immune response that attracts the white blood cells of inflammation to the muscles.

Patients with calcium deposits (calcinosis) from dermatomyositis can sometimes benefit by taking diltiazem (Cardizem) which shrinks the size of the calcium deposits. This effect, however, occurs over years and is not always effective.

Patients can ultimately do well, especially with early medical treatment of disease and disease flares. The disease frequently becomes inactive, and rehabilitation of atrophied muscle becomes a long-term project.

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Treatment for Polymyositis and Dermatomyositis In Thousand Oaks

If you are suffering from polymyositis or dermatomyositis, there is help for you at Cohen Medical Centers. Dr. Cohen and his talented team are ready to help you feel like yourself again and prevent your condition from getting worse. To learn more about our treatment options in Ventura County, call us at (805) 449-8781 to schedule your consultation.

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