What Are the Causes of Myositis

Autoimmune

The most common cause of myositis is from the body attacking its own muscle tissues, according to The Myositis Association. Because of this self-attack, some types of myositis are autoimmune diseases by classification. For unknown reasons, genetics or outside forces trigger the immune system, causing the attacks. Normally, the immune system works to protect the body from becoming infected with foreign invaders, such a bacteria. When triggered by an unknown cause, the immune system mistakes the muscle tissue as a foreign object and produces autoimmune antibodies to attack. This attack causes the inflammation and swelling within the muscle. Blood test results in individuals with myositis display an increased number of autoimmune antibodies and white blood cells. Both of these indicate an autoimmune attack on the muscle tissue.

According to the Muscular Dystrophy Association, certain medications cause inflammation within the muscle tissue. Exposure to these drugs causes myositis, and cessation will make it end. Some of the suspected medications that may cause myositis include cholesterol-lowering medicines. Penicillamine, which is used to lower copper levels in the body, and carticaine, an anesthetic, are both considered possible causes of the attack on the muscles. Additionally, interferon-alpha, used to treat hepatitis and cancer, causes the body to be susceptible to muscle attacks. Carbimazole, cimetidine, phenytoin and growth hormones are medications with the ability to increase the risk of myositis. Although it is not a medication, the hepatitis B vaccine may cause myositis. If any medications cause inflammation and edema in muscle tissue, immediately stopping the medication to prevent further damage to the muscle is essential.

An injury to the muscle, such as a car accident or sporting incident, might cause edema and inflammation to the tissue. The injury resolves in time and the condition is not chronic, as with autoimmune myositis. According to the Muscular Dystrophy Association, viruses have the ability to trigger autoimmune myositis symptoms. Individuals infected with the HIV, which causes AIDS, can develop myositis from the viral infection. Also, people infected with HTLV-1 (human T-lymphocyte virus-1) have an increased likelihood of muscle inflammation. Some reports of myositis occurred after an infection with the coxsackie virus.