Polymyositis

One of the conditions we see often is a condition called polymyositis. This is a condition of an inflammation of the muscle groups. It is very similar to a condition called dermatomyositis which is distinguished by not only having muscle involvement, but also by having a typical skin rash around the face, eyes, back of the hands and extremities.

Polymyositis may present in childhood, middle age or old age and depending on the age may have different significance. The childhood form is a very serious form, which often causes severe muscle weakness and it can be difficult to treat. The elderly form may at times be a tip off that there is some underlying more serious condition, such as a malignant condition, existing and that possibility needs to be looked for carefully. The more common type occurring in the young to middle age group relates to an autoimmune disease that causes a fairly progressive onset of pain and weakness in the muscles especially affecting the head and neck, the shoulder girdle and the lower extremities. People who have this condition may notice that they are having difficulty getting off of a chair, getting in and out of a car, and that exerting minimal effort causes significant fatigue in their muscles.

The condition is diagnosed by the clinical finding as well as by performing some blood tests. The most diagnostic blood test is the CPK which is a measurement of the enzymeproduced by muscle breakdown. The higher the CPK level the more inflammation that is on-going in the muscles. The disease activity is directly related to the CPK level. The diagnosis can be confirmed by having an electrical study called an EMG or by having a biopsy.

The treatment ranges from using corticosteroids to immunosuppressive drugs. In general, the treatment will be very effective especially when the diagnosis is made early. Unfortunately, this diagnosis is often missed until the disease is advanced and has caused severe weakness and muscle wasting. It is also important to recognize that muscles need to be rested and that exercise aggravates this condition.

There are, at times, patients who may have organ involvement, in particular the heart, as part of this condition. In fact, in patients with cardiomyopathy, there is an enlarged heart, which can be a cause of death in a small number of patients.

One of the most common causes in this day and age of polymyositis is the use of the cholesterol lowering drug, like the statins Zocor, Lipitor, and Pravachol. It is common to see low grade cases of muscle inflammation secondary to the use of this class of drugs and patients having this particular side effect need to be followed.

Author: Norman B. Gaylis, MD, FACP, FACR

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