Polymyositis - Causes, Symptoms, Treatment
Polymyositis (PM), dermatomyositis (DM), and inclusion body myositis (IBM) are the major members of a group of skeletal muscle diseases called the idiopathic inflammatory myopathies. Clinical features, characteristic muscle biopsy findings, immune markers, and histopathologic findings differentiate these illnesses. No strictly defined diagnostic criteria for PM or DM exist; however, Bohan and Peter proposed the criteria most widely cited. These criteria include the typical rash of DM, findings at history and physical examination that reveal symmetric proximal muscular weakness, elevated serum muscle enzyme levels, electromyographic evidence of myopathic abnormalities, and characteristic findings at muscle biopsy.
Causes
To date, no cause of polymyositis has been isolated by scientific researchers. There are indicators of heredity (genetic) susceptibility that can be found in some patients. There is indirect evidence of infection by a virus that has yet to be identified in a form of polymyositis that is particularly resistant to treatment, called inclusion body myositis. This form of polymyositis is diagnosed by the pathologist, a physician specialist who interprets the microscope findings of muscle tissue.
Symptoms
Signs and symptoms of polymyositis usually appear gradually, so it may be difficult to pinpoint when they first started. They may also fluctuate from week to week or month to month.
The symptoms of polymyositis and dermatomyositis often develop slowly in adults. In children, however, they may occur rapidly. Weakness of the muscles that form the pelvic-girdle and shoulder-girdle muscles, is common. It results in difficulties raising the arms and difficulties getting up from a sitting position. There may be difficulties swallowing or speaking. Fatigue is common and mild fever may occur.
Diagnosis
Diagnosis is fourfold, including elevation of creatine kinase, signs and symptoms, electromyograph (EMG) alteration, and a positive muscle biopsy. Treatment generally involves glucocorticoids, especially prednisone. At present, a number of studies are underway to determine whether patients diagnosed with polymyositis will benefit from newer drugs inhibiting the biologic effects of TNF alpha, such as infliximab.
Treatment
There is no cure for polymyositis, but the symptoms can be treated. Options include medication, physical therapy, exercise, heat therapy (including microwave and ultrasound), orthotics and assistive devices, and rest. The standard treatment for polymyositis is a corticosteroid drug, given either in pill form or intravenously. Immunosuppressant drugs, such as azathioprine and methotrexate, may reduce inflammation in people who do not respond well to prednisone. Periodic treatment using intravenous immunoglobulin can also improve recovery. Other immunosuppressive agents used to treat the inflammation associated with polymyositis include cyclosporine A, cyclophosphamide, and tacrolimus.
