The word myositis describes numerous diseases that trigger muscular inflammation. These include dermatomyositis and polymyositis. Myositis is also a symptom of autoimmune diseases such as rheumatoid arthritis, lupus and scleroderma. Every year, five to 10 out of every 1 million American adults gets some form of myositis, estimates the Arthritis Foundation. Increased muscle enzyme activity may cause the inflammation associated with this disease.
Causes and Symptoms
Scientists do not know the exact causes of myositis, but speculate that exposure to certain chemicals, drugs or viruses may trigger the disease, says the Arthritis Foundation. Ultraviolet light and stress are other possible causes. Causes vary according to the specific disease, but elevated muscle enzymes might trigger the inflammation, says Dr. Lawrence J. Kagen, Attending Rheumatologist at the Hospital for Special Surgery.
Symptoms
Myositis patients report flareups and remission periods, which come and go without warning. During a flareup, you might experience muscle inflammation, muscle weakness, chronic fatigue, skin rashes and difficulty swallowing. Some people have trouble speaking clearly during a flareup. Myositis affects your ability to perform simple, everyday tasks such as combing your hair, putting on your clothes, getting in and out of the bathtub or climbing up the stairs. Your symptoms help your doctor diagnose your specific form of myositis.
Autoimmunity
Doctors characterize the resulting inflammation from myositis as an autoimmune response. Your immune system has groups of cells called lymphocytes, whose tasks resemble those performed by your local neighborhood watch. Lymphocytes roam throughout your body and attack viruses, bacteria and other disease-causing agents. In healthy people, lymphocytes recognize the difference between your body's muscle cells and a foreign bacteria. People with autoimmune disorders have overactive lymphocytes, which attack your own muscle cells. The attack may increase muscle enzyme activity, which in turn causes inflammation.
Types
Dermatomyositis is an acquired inflammatory muscle disorder that also damages your skin. Afflicted patients experience muscle weakness in the neck, shoulders, trunk and hips. A red or purple skin rash on the upper chest, cheeks, nose, back, eyelids, elbows, knees
and knuckles often accompanies this disease. Elevated muscle enzymes such as creatine
phosphokinase may cause dermatomyositis, says the neurology department at Washington State University. Treatments include immunosuppressive drugs such as corticosteroids and methotrexate, as well as intravenous immunoglobulin. Polymyositis, while similar to dermatomyositis, does not usually involve skin rashes.
