Polymyositis is one of a group of diseases termed idiopathic in-flammatory myopathies. It is a rare condition with an incidence that is estimated to be from fewer than one to eight cases per million (Ruddy et al., 2001).
Polymyositis is classified as autoimmune because autoantibodies are present. However, these antibodies do not cause damage to muscle cells, indicating only an indirect role in tissue damage. The pathogenesis is multifactorial, and a genetic predisposition is likely. Drug-induced disease is rare. Some evidence suggests a viral link.
The onset varies from sudden onset with rapid progression to a very slow, insidious onset. Proximal muscle weakness is typically a first symptom. Muscle weakness is usually symmetric and dif-fuse. Dermatomyositis, a related condition, is most commonly identified by an erythematous smooth or scaly lesion found over the joint surface.
A complete history and physical examination help to exclude other muscle-related disorders. As with other diffuse connective tissue disorders, no one test confirms polymyositis. An electro-myogram is performed to rule out degenerative muscle disease. A muscle biopsy may reveal inflammatory infiltrate in the tissue. Serum studies indicate increased muscle enzyme activity.
Management involves high-dose corticosteroid therapy initially, followed by a gradual dosage reduction over several months as muscle enzyme activity decreases. Patients who do not respond to corticosteroids require the addition of an immunosuppressive agent. For patients who are unresponsive to corticosteroids and immunosuppressive medications, plasmapheresis, lymphaphere-sis, and total-body irradiation have been used. Skin rashes may respond to the antimalarial drug hydroxychloroquine. Physical therapy is initiated slowly with range-of-motion exercises to maintain joint mobility, followed by gradual strengthening exer-cises (Klippel, 2001).
Nursing care is based on the basic plan of nursing care presented earlier. The most frequent nursing diagnoses for the patient with polymyositis include impaired physical mobility,fatigue, self-care deficit, and insufficient knowledge of self-management techniques.
Patients with polymyositis may have symptoms similar to those of other inflammatory diseases. However, proximal muscle weakness is characteristic, making activities such as combing hair, reaching overhead, and using stairs difficult. Therefore, use of as-sistive devices may be recommended and referral to occupational or physical therapy may be warranted.