Polymyositis is a type of inflammatory myopathy, a muscle disease that causes weak and inflamed skeletal muscles. According to the Mayo Clinic, polymyositis mainly affects adults between 30 and 50 years old, although it can strike individuals of any age. Polymyositis is fairly rare, affecting only 1 in 100,000 people, according to Medline Plus.
Symptoms
The effects of polymyositis can be seen all over the body, but they begin slowly, so they may be difficult to identify at first. The main symptom is a gradual weakening of the muscles, beginning in the main trunk and spreading to the limbs over time, according to the National Institute of Neurological Disorders and Stroke. Eventually, weakness is so severe that the afflicted individual may not be able to comfortably rise from a seated position, lift his hands above his head or climb stairs. The disease may affect the vocal cords, causing difficulty speaking. Breathing difficulty, heart arrhythmias and arthritis may also show up as signs of polymyositis.
Causes and Risk Factors
The exact cause of polymyositits is not known, but scientists suspect an autoimmune reaction or viral infection may be involved, according to Medline Plus. People of African descent are more likely to develop the condition than Caucasians, and more women than men develop the disease.
Treatment
Doctors typically prescribe corticosteroid medications such as prednisone to treat polymyositis, according to the National Institute of Neurological Disorders and Stroke. With corticosteroid treatment, muscle tone usually improves within 4 to 6 weeks, and the person is then weaned off the medication or given prednisone on an indefinite basis to prevent recurrence. For people who don't improve with corticosteroids, immune suppressors may be tried. These can include azathioprine, methotrexate, cyclosporine A, cyclophosphamide, tacrolimus or intravenous immunoglobulin. Physical therapy and assistive devices may also be used during a treatment program.
Complications
Over time, polymyositis may cause long-term muscle weakness that makes everyday activities difficult. When it affects the muscles surrounding the throat and chest, respiratory failure, pneumonia and breathing problems may result. Malnutrition and calcium deposits that form in the muscles may also develop as a result of the disease. Lung disease and cardiovascular disease are associated with polymyositis, but are not directly caused by the disease.
Tests
Diagnosing polymyositis usually first involves a visual inspection by the doctor. Imaging tests such as MRIs can look for areas that may be affected. Blood tests are used to look for elevated levels of creatine kinase and aldolase, muscle enzymes that may indicate damage when found at high levels in the blood. Some doctors perform a muscle biopsy or an electromyography to look at patterns of muscle activity.
