Polymyositis is a rheumatic disease, such as psoriatic arthritis, which causes inflammation, pain and weakness in the muscles. Its origin is not clear but may be caused by an autoimmune reaction or infection of a muscle. Polymyositis is chronic, it affects the whole body and general symptoms are pain and muscle weakness, shortness of breath, fatigue and tiredness for walking, fever or weight loss, among others. The disease has no cure, but the patient can regain muscle strength steroid. With this therapy may reduce symptoms and provide a normal life for the sick. If this treatment fails, the affection can be controlled with immunosuppressive. In some cases, this polymyositis associated with a tumor, in which case it is necessary to proceed to remove it.