Polymyositis is one of autoimmune diseases. It is present more in women and it affects the muscle tissue.
The causes of the disease are not clear. The immune system of the patient begins to attack its own tissues, in this case the muscles. There are more mechanisms of the damage including production of aggressive autoantibodies. In adults, there is an important coincidence between the polymyositis and various malignant diseases, i.e. some cases of polymyositis can occur in patients with a cancer (usually not yet diagnosed).
The primary symptom is muscle pain, muscle weakness and general fatigue. The disease can cause troubles when walking or lifting the upper extremities. Disorders of muscles in the digestive tract can cause swallowing disorders. Chronic forms of the disease are related to muscle atrophy and pulmonary fibrosis leading to shortness of breath during physical exercise. Rarely, the process develops into a strong inflammation with total disintegration of muscle fibers, which is professionally known as the rhabdomyolysis.
There may be also present some skin symptoms and in such case we talk about the dermatomyositis. Red spots occur on the joints of the fingers and the affected skin gets thicker and rougher. The hands of the patient may resemble hands of a hard manual worker (the so-called mechanic’s hands).
In addition to typical symptoms, there are elevated serum concentrations of various muscle enzymes that disengage from the damaged muscle fibers, for example the enzyme creatine kinase (CK). The diagnosis may be probably by a positive serological examination of the blood, where we find presence of various autoantibodies. The most invasive and most reliable examination is a muscle biopsy, where we take a small sample of muscle tissue by a fine needle. The histological examination can confirm the typical chronic inflammatory changes. In an adult patient with a confirmed polymyositis, it is wise to perform at least basic examinations to rule out the presence of a malignant disease.
The disease tends to occur in bouts alternated with periods of calm. During the attacks, it is recommended to avoid physical activity and overload of the muscular apparatus. When the disease is calm, reasonable rehabilitation is possible. The pharmacotherapy includes a variety of immunosuppressive drugs, particularly corticosteroids.