Diagnosis

To diagnose polymyositis, a healthcare professional does a physical exam and checks muscle strength. The following tests may help with diagnosis:

  • Blood tests. A blood test may show higher levels of muscle enzymes, which can mean muscle damage. A blood test also can detect immune cells called autoantibodies linked with certain symptoms of polymyositis.
  • Electromyography. For this test, a healthcare professional puts a thin needle electrode through the skin and into the muscle. The test measures electrical activity of the muscles as they relax or tighten. Changes in the pattern of electrical activity can confirm a muscle disease. Testing different muscles can show which ones the condition affects.
  • MRI. A magnetic field and radio waves from a computer make detailed pictures of the muscles. An MRI can find swelling and irritation, called inflammation, over a large area of affected muscle.
  • Muscle biopsy. A healthcare professional removes a small piece of muscle tissue to send to a lab for study. The results can show muscle damage and swelling and irritation, called inflammation. A biopsy may be needed to diagnose polymyositis.
  • Lung tests. Your healthcare professional may suggest tests to see how well the lungs work and a CT of the chest. You may have these tests if you have certain autoantibodies that have been linked with a condition of lung scarring called interstitial lung disease that may happen with dermatomyositis.

Treatment

There's no cure for polymyositis. But treatment can improve muscle strength and help muscles work better. Your healthcare professional bases your treatment on your symptoms and how well the treatment manages them.

Medications

The most common medicines to treat polymyositis include:

  • Corticosteroids. Medicines such as prednisone can manage polymyositis symptoms well. But using these medicines over time can cause serious side effects, including muscle weakness. So your healthcare professional tapers the dosage little by little.
  • Corticosteroid-sparing agents. When used with a corticosteroid, these medicines may allow for a lower dosage of the corticosteroid and fewer side effects. The two most common medicines for polymyositis are azathioprine (Azasan, Imuran) and methotrexate (Trexall, Xatmep).
  • Medicines for more-serious illness. Other medicines for polymyositis include mycophenolate mofetil (CellCept, Myhibbin), cyclosporine (Gengraf, Neoral, others), tacrolimus (Astagraf XL, Prograf, others) and rituximab (Rituxan). These medicines can lessen the need for long-term corticosteroids.

  • Intravenous immunoglobulin. Also called IVIg, this purified blood product has healthy antibodies from thousands of blood donors. These healthy antibodies can block the antibodies that attack muscle in polymyositis.

    Treatment with IVIg involves getting the medicine through a vein, called an infusion. IVIg treatments may be used regularly or sometimes. The treatment mainly helps with trouble swallowing.

Therapy

Depending on the how serious the symptoms are, treatment might include:

  • Physical therapy. A physical therapist can show you exercises to improve your strength and tell you what level of activity is right for you.
  • Speech therapy. If polymyositis weakens muscles used for swallowing, speech therapy can help you learn how to work with the weakness.
  • Nutrition help. Over time, polymyositis can make it harder to chew and swallow. A registered dietitian can teach you how to make easy-to-eat foods that give you enough nutrition.

Coping and support

Living with a chronic condition can be a challenge. To help you cope, try adding the following suggestions to your medical care:

  • Know your illness. Read all you can about polymyositis and other muscle conditions. Talk with people who have conditions like yours. Ask your healthcare professional any questions that you have about your condition, diagnosis or treatment.
  • Be a part of your medical team. Work with the healthcare professionals involved in your care. Follow your treatment plan, including physical therapy. Tell your healthcare team about any new symptoms you have.
  • Know your limits. Ask for help when you need it. And let others know about the ways polymyositis limits you.
  • Rest when you're tired. Don't wait until you're worn out. Learn to pace yourself so that you keep up your energy level, get done what you need to do and feel better mentally.

  • Accept your feelings. Dealing with an ongoing illness may cause anger, sadness and other feelings. You might feel like your life is out of control and that you're alone.

    Stay close to family and friends. Stick to your daily routine as best you can. Do things you enjoy. Many people find support groups helpful.

Preparing for your appointment

Start by seeing your main healthcare professional, who might send you to a specialist in conditions of the joints, muscles and bone, called a rheumatologist. Or you might see a specialist in conditions of the nervous system, called a neurologist.

What you can do

Make a list of:

  • Your symptoms, including when they began and which muscles are affected.
  • Key personal information, including major stresses, recent life changes, and your and your family's medical history.
  • All medicines, vitamins and other supplements you take, including the dosages.
  • Questions to ask your healthcare professional.

For polymyositis, some questions to ask include:

  • What is the likely cause of my symptoms?
  • What are other possible causes for my symptoms?
  • What tests do I need? Do I need to do anything to prepare for them?
  • What treatments do you suggest?
  • I have other medical conditions. How can I best manage them together?
  • Do you have brochures or other printed material that I can have? What websites do you suggest?

Be sure to ask all the questions you have.

What to expect from your doctor

Your healthcare professional may ask you questions, such as:

  • Did your symptoms come on slowly or did they start all at once?
  • Do you easily tire during waking hours?
  • What does your condition keep you from doing?
  • Has anyone in your family been diagnosed with a condition that affects the muscles?
  • What, if anything, seems to make your symptoms better?
  • What, if anything, seems to make your symptoms worse?
By Mayo Clinic Staff