Polymyositis (pol-e-my-o-SY-tis) is an uncommon inflammatory disease that causes muscle weakness affecting both sides of your body. Having this condition can make it difficult to climb stairs, rise from a seated position, lift objects or reach overhead.
Polymyositis most commonly affects adults in their 30s, 40s or 50s. It's more common in blacks than in whites, and women are affected more often than men. Signs and symptoms usually develop gradually, over weeks or months.
While there is no cure for polymyositis, treatment — ranging from medications to physical therapy — can improve your muscle strength and function.
The muscle weakness associated with polymyositis involves the muscles closest to the trunk, such as those in your hips, thighs, shoulders, upper arms and neck. The weakness affects both the left and right sides of your body, and tends to gradually worsen.
When to see a doctor
Seek medical attention if you develop unexplained muscle weakness.
The exact cause of polymyositis is unknown, but the disease shares many characteristics with autoimmune disorders, in which your immune system mistakenly attacks your own body tissues.
Your risk of polymyositis is higher if you have lupus, rheumatoid arthritis, scleroderma, or Sjogren's syndrome.
Possible complications of polymyositis include:
- Difficulty swallowing. If the muscles in your esophagus are affected, you may have problems swallowing (dysphagia), which in turn may cause weight loss and malnutrition.
- Aspiration pneumonia. Difficulty swallowing may also cause you to breathe food or liquids, including saliva, into your lungs (aspiration), which can lead to pneumonia.
- Breathing problems. If your chest muscles are affected by the disease, you may experience breathing problems, such as shortness of breath or, in severe cases, respiratory failure.
Although these are not complications, polymyositis is often associated with other conditions that may cause further complications of their own, or in combination with polymyositis symptoms. Associated conditions include:
- Raynaud's phenomenon. This is a condition in which your fingers, toes, cheeks, nose and ears initially turn pale when exposed to cold temperatures.
- Other connective tissue diseases. Other conditions, such as lupus, rheumatoid arthritis, scleroderma and Sjogren's syndrome, can occur in combination with polymyositis.
- Cardiovascular disease. Polymyositis may cause the muscular walls of your heart to become inflamed (myocarditis). In a small number of people who have polymyositis, congestive heart failure and heart arrhythmias may develop.
- Lung disease. A condition called interstitial lung disease may occur with polymyositis. Interstitial lung disease refers to a group of disorders that cause scarring (fibrosis) of lung tissue, making lungs stiff and inelastic. Signs and symptoms include a dry cough and shortness of breath.
- Cancer. People who have polymyositis have an elevated risk of cancer.
If your doctor suspects you have polymyositis, he or she might suggest some of the following tests:
- Blood tests. A blood test will let your doctor know if you have elevated levels of muscle enzymes, which can indicate muscle damage. A blood test can also detect specific autoantibodies associated with different symptoms of polymyositis, which can help in determining the best medication and treatment.
- Electromyography. This test involves inserting a thin needle electrode through the skin into the muscle. Electrical activity is measured as you relax or tighten the muscle, and changes in the pattern of electrical activity can confirm a muscle disease. The doctor can determine the distribution of the disease by testing different muscles.
- Magnetic resonance imaging (MRI). A scanner creates cross-sectional images of your muscles from data generated by a powerful magnetic field and radio waves. Unlike a muscle biopsy, an MRI can assess inflammation over a large area of muscle.
- Muscle biopsy. During this test, a small piece of muscle tissue is surgically removed for laboratory analysis. Analysis may reveal abnormalities, such as inflammation, damage, certain proteins or enzyme deficiencies.
Although there's no cure for polymyositis, treatment can improve your muscle strength and function. The earlier treatment is started in the course of polymyositis, the more effective it is — leading to fewer complications.
However, as with many conditions, no single approach is best; your doctor will tailor your treatment strategy based on your symptoms and how well they respond to therapy.
The most commonly used medications to treat polymyositis include:
- Corticosteroids. Drugs such as prednisone can be very effective in controlling polymyositis symptoms. But prolonged use of these drugs can have serious and wide-ranging side effects, which is why your doctor may gradually taper the dose of medication down to lower levels.
- Corticosteroid-sparing agents. When used in combination with a corticosteroid, these drugs can decrease the dose and potential side effects of the corticosteroid. The two most common medications used for polymyositis are azathioprine (Azasan, Imuran) and methotrexate (Trexall). Other medications prescribed for polymyositis include mycophenolate mofetil (CellCept), cyclosporine and tacrolimus.
- Rituximab (Rituxan). More commonly used to treat rheumatoid arthritis, rituximab is an option if initial therapies don't adequately control your polymyositis symptoms.
Depending on the severity of your symptoms, your doctor might suggest:
- Physical therapy. A physical therapist can show you exercises to maintain and improve your strength and flexibility and advise an appropriate level of activity.
- Speech therapy. If your swallowing muscles are weakened by polymyositis, speech therapy can help you learn how to compensate for those changes.
- Dietetic assessment. Later in the course of polymyositis, chewing and swallowing can become more difficult. A registered dietitian can teach you how to prepare easy-to-eat, nutritious foods.
Surgical and other procedures
Intravenous immunoglobulin (IVIg) is a purified blood product that contains healthy antibodies from thousands of blood donors. These healthy antibodies can block the damaging antibodies that attack muscle in polymyositis. Given as an infusion through a vein, IVIg treatments may need to be repeated regularly for the effects to continue.
Coping and support
Living with a chronic autoimmune disease can make you wonder at times whether you're up to the challenge. To help you cope, try supplementing your medical care with the following suggestions:
- Know your illness. Read all you can about polymyositis and other muscle and autoimmune disorders. Talk to other people who have a similar condition. Don't be afraid to ask your doctor any questions that you may have concerning your illness, diagnosis or treatment plan.
- Be a part of your medical team. Consider yourself, your doctor and any other medical experts involved as a united front in the fight against your disease. Following the treatment plan you agreed to is vital. Keep your doctor updated on any new signs or symptoms you may experience.
- Know and assert your limits. Learn to say no effectively and ask for help when you need it.
- Rest when you're tired. Don't wait until you're exhausted. This will only set you back further as your body tries to recuperate. Learning to pace yourself can help you maintain a consistent level of energy, accomplish just as much and feel better emotionally.
- Acknowledge your emotions. Denial, anger and frustration are normal feelings when you must deal with an illness. Things don't seem normal or fair and likely seem out of your control. Feelings of fear and isolation are common, so stay close to your family and friends. Try to maintain your daily routine as best you can and don't neglect doing those things you enjoy. Many people find support groups to be a helpful resource.
Preparing for an appointment
You'll probably first bring your symptoms to the attention of your family doctor. He or she might refer you to a doctor who specializes in the treatment of arthritis and other diseases of the joints, muscles and bone (rheumatologist) or to a doctor who specializes in disorders of the nervous system (neurologist).
What you can do
When you go in to see your doctor, be sure to have a record of your symptoms. Although it may be difficult to pinpoint when symptoms started, try to estimate when you first noticed weakness, and which muscles have been affected. You may want to write a list that includes:
- Detailed descriptions of your symptoms, including which muscles are affected
- Information about medical problems you've had
- Information about the medical problems of your parents or siblings
- All the medications and dietary supplements you take
- Questions you want to ask the doctor
Prepare a list of questions ahead of time to help make the most of your limited time with your doctor. For polymyositis, some basic questions to ask your doctor include:
- What is likely causing my symptoms?
- Are there other possible causes for my symptoms?
- Are my symptoms likely to change over time?
- What kind of tests might I need? Are any special preparations required?
- Are treatments available for my condition? What treatments do you recommend?
- I have other medical conditions. How can I best manage them together?
- Do you have any brochures or other printed material that I can take with me? What websites do you recommend?
In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask questions during your appointment if you think of something new.
What to expect from your doctor
Your doctor will likely ask you several questions, such as:
- When did you first notice muscle weakness?
- Did your condition develop gradually or did it come on suddenly?
- Are you easily fatigued during waking hours?
- What other symptoms are you experiencing?
- Does your condition limit your activities?
- Has anyone in your family ever been diagnosed with a disease or condition that affects the muscles?
- Are you currently taking any medications or dietary supplements?
- What, if anything, seems to improve your symptoms?
- What, if anything, appears to worsen your symptoms?
Content Last Updated: July 1, 2020