Myositis is a general term used for any condition that involves muscle swelling. "Myo" refers to muscles and "itis" means inflammation. In this rare disease, the immune system inflames the body's own muscle tissue. Most conditions that fall under this category are triggered by autoimmune diseases. Autoimmune diseases occur when the immune system attacks the body's own healthy tissues.
Causes of Myositis
Myositis can be caused by several factors. These causes are divided into several classifications. Falling under the first category are inflammatory conditions such as dermatomyositis, polymyositis, and inclusion body myositis. These autoimmune diseases inflame the muscles throughout the body, resulting in myositis. Some inflammatory conditions like systemic lupus erythematosus (lupus), scleroderma and rheumatoid arthritis produce only mild myositis. Nevertheless, everything that falls under the first category are said to be the most serious type of myositis that require extensive treatment.
The second category is infection. The most common infection that leads to myositis is the viral one. There are also times when bacterial and fungal infection trigger muscle inflammation. Viruses, bacteria and fungi can either invade the muscles directly or produce substances that bring damage to the fibers of the muscles. Myositis can be caused by common viral infections like colds and flu as well as life-threatening ones like the human immunodeficiency virus (HIV).
The third category is drugs. A side effect of certain medications is temporary muscle damage. But since the muscle inflammation due to drugs is often not identified, it may be diagnosed as myopathy instead of myositis. Statins, colchicine, plaquenil (hydroxychloroquine), alpha-interferon, cocaine and alcohol are just some of the drugs that can cause myopathy and myositis. The muscle inflammation can start immediately after taking in the medication or after consuming it regularly for months or even years. It's good to know though that medications rarely cause severe myositis.
The fourth category is injury. Any injury to the muscle group that can lead to muscle swelling, pain and weakness falls under this group. Symptoms felt after exercise or injury can go away without any treatment. Only proper rest is recommended.
The fifth and final category is rhabdomyolysis. This happens where there is muscle breakdown in the large muscle groups. Its symptoms include muscle swelling, pain and weakness and dark brown or red urine.
Symptoms of Myositis
Muscle weakness is the most noticeable symptom of myositis. Myalgias or muscle pain may also be felt. Myositis caused by inflammatory conditions produces pain and weakness that progress gradually over several weeks to a few months. Often, the large muscle groups like the hips, shoulders, back and neck are affected. Other symptoms include rash, fatigue, difficulty in swallowing and breathing, and thickening of the skin on the hands.
Myositis caused by viral infection produce symptoms of a viral infection like fever, cough, stuffy nose, diarrhea and nausea. These symptoms usually subside even before the muscle inflammation sets in.
Treatment of Myositis
The treatment for myositis depends on the cause. Those that are caused by inflammatory conditions are treated with immune system-suppressing medications like Prednisone, Imuran (azathioprine) and Methotrexate. Those caused by viruses or injuries don't require any specific medical treatment other than home remedies like rest. If the myositis is caused by bacterial infection, intravenous antibiotics are needed to prevent the spread of infection. Hospitalization is necessary for myositis cases brought about by rhabdomyolysis. A person is recommended to discontinue taking drugs that cause myositis.