Definition
Polymyositis is a disease of the muscles. It usually affects the muscles closest to the trunk of the body. However, it may affect muscles anywhere in the body. The muscles become inflamed or swollen. This causes pain. The disease is progressive and starts slowly. If untreated, the muscles gradually become weaker. The pain in the muscles also increases.
This rare disease is believed to be an autoimmune disorder. Your immune system is your body’s defense system. It fights diseases and infections. In this case your immune system attacks your own muscle tissue by mistake.
The sooner the disease is treated, the better the outcome. If you suspect you have this condition, contact your doctor.
Causes
The cause is unknown. Factors that may contribute to polymyositis include:
- Genetics
- A virus that sets off the condition
- A reaction to certain drugs that set off the condition
Risk Factors
The following factors increase your chance of developing polymyositis:
- Age: 50-70 years old
- Gender: Women are more likely to develop polymyositis than men.
Symptoms
Symptoms include:
- General weakness (lethargy)
- Weakness in the muscles of the hips and shoulders—occurs slowly and gradually over a period of weeks or even months
- This gradual muscle weakness is often the first sign of the disease
- Achy, tender muscles
- Weight loss
- Fatigue after standing or walking
- Trouble rising from a chair
- Great effort needed to climb stairs
- Struggle to lift objects
- Difficulty reaching overhead (eg, unable to comb your hair)
- Trouble with swallowing (when muscles in the front of the neck and throat become involved)—rare
- Difficulty breathing (if it affects the lungs or chest muscles)—rare
Diagnosis
This diagnosis is not easy. Symptoms vary from person to person. It is often a matter of ruling out other diseases and conditions. Your doctor will ask about your symptoms and medical history. A physical exam will be done.
Tests may include the following:
- Blood test—to check for autoantibodies (antibodies that attack parts of your body)
- Creatine kinase test—blood test that looks for elevated levels of muscle proteins or enzymes called creatine kinase (CK) (when a muscle is damaged, CK is released into the bloodstream)
- Aldolase test—a blood test that looks for elevated levels of aldolase (a substance released into the bloodstream when a muscle is damaged)
- Electromyogram (EMG) —measures activity of your muscles, often used to help find causes of muscle weakness or damage
- Muscle biopsy —a small piece of muscle tissue is removed and examined to see if the muscle is damaged in some way
- Magnetic resonance imaging (MRI) —noninvasive scan, using magnetic waves, of your muscles to see if any muscles are inflamed
Treatment
While there is no cure, treatment can improve your muscle strength and function. Talk with your doctor about the best plan for you. Options include:
Medication
There are a number of medicines that may be prescribed. Corticosteroids (eg, prednisone ) are usually one of the first treatments that are tried. These medicines work by suppressing the immune system, which reduces inflammation. In some cases, it may take 3-6 months to have an improvement in symptoms.
Other medicines that may be recommended instead of prednisone include:
- Methotrexate (eg, Rheumatrex, Trexall)
- Azathioprine (eg, Azasan, Imuran)
- Other drugs to suppress the immune system, such as cyclosporine (eg, Gengraf, Neoral, Restasis), chlorambucil (eg, Leukeran)
Intravenous immunoglobulin is another treatment option that involves using an IV needle to inject extra immunoglobins (special proteins) into the body. This process may help the immune system function better and reduce inflammation.
In severe cases of polymyositis, the doctor may recommend investigational drugs, such as:
- Rituximab (Rituxan)
- Tumor necrosis factor (TNF) inhibitors (eg, etanercept [Enbrel], infliximab [Remicade])
Physical Therapy
Your doctor may recommend that you work with a physical therapist to prevent permanent muscle damage. Exercise may include:
- A regular stretching routine for weakened arms and legs
- Light strengthening as the pain lessens and function returns
Dietary Changes
Polymyositis can lead to problems with chewing and swallowing. By working with a registered dietician, you can learn ways to adjust to these changes and get the nutrition that you need.
Speech Therapy
Polymyositis may also cause speech problems. A speech therapist can assess your condition and create a program for you.
Prevention
There are no known ways to prevent polymyositis.