Polymyositis

What Is Polymyositis?

Polymyositis is a type of muscle disease called an inflammatory myopathy. It inflames your muscles and their related tissues, like the blood vessels that supply them. It can cause muscle weakness and pain, often on both sides of your body. There’s no cure for this ongoing (chronic) condition, but there are treatments that can help with symptoms.

Causes and Risk Factors for Polymyositis

No one knows the exact cause of polymyositis. But doctors do know that it’s an autoimmune condition, which means the body can attack its own tissues. This is what causes the problems.

It’s more common in people with other autoimmune diseases like lupus and rheumatoid arthritis. It’s also more common among people with HIV.

Most people who have polymyositis get diagnosed between the ages of 30 and 60. It’s very rare in children, and it affects women more often than men.

Risk factors for polymyositis include:

 

Symptoms of Polymyositis

The symptoms of polymyositis are caused by inflammation in the muscles. The muscle weakness affects both sides of the body equally.

The condition tends to target the muscle groups that are closest to the trunk of the body -- the hips, shoulders, thighs, upper arms, upper back, and neck.

If you have it, you may notice you have trouble lifting your arms over your head, walking up flights of stairs, rising from a chair, or carrying things. In some cases, it may be hard to swallow food, but this is unusual.

You may or may not have pain in the areas where the muscles are weak. Over time, the muscles may atrophy, meaning they waste away or become less bulky. The condition often worsens slowly, and you might not notice symptoms for months.

Muscle weakness may be one of the first symptoms you do notice. You may also feel you just can’t do all the things you used to. You may also have:

  • Fever
  • Weight loss
  • Fatigue
  • Joint pain
  • Raynaud’s phenomenon, a condition in which the fingers or toes become very cold and discolored due to problems with blood flow.

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Diagnosis of Polymyositis

There are no simple tests to diagnose polymyositis. It often takes time before doctors know for sure you have it.

Your doctor will consider your medical history, and your family’s, to rule out other conditions. You may also get tests such as:

  • Blood tests: These can help the doctor spot signs of muscle damage.
  • EMG (electromyography): Checks to see if the patterns of electrical impulses in your muscles are normal or not
  • MRI (magnetic resonance imaging): This uses a magnet to scan and create images of large areas of muscle.
  • Muscle biopsy: Your doctor will take a small sample of your muscle for testing to see if the muscle tissue is inflamed. You may need to get an MRI to help your doctor find a good spot to biopsy.

Treatment of Polymyositis

Polymyositis is a chronic condition. That means that once you have it, it sticks around. But there are ways to help manage it.

Common treatments include:

  • Steroids . These help with muscle inflammation, ease pain, and even increase muscle strength. But steroids can have many side effects, so when your doctor prescribes them, he’ll keep an eye on you. Most people start with prednisone, but if you have a severe case, the doctor may add methylprednisone, too.
  • Drugs that suppress the immune system. You may take these with steroids, or on their own if steroids don’t help. The doctor will probably start you off with azathioprine or methotrexate.
  • Physical therapy . This will make you stronger and help you move better.

Ask your doctor about any questions you have, and for other ways to make your life easier.

Complications of Polymyositis

Complications that might come along with polymyositis include:

  • Trouble swallowing: This could happen if the muscles in your esophagus are affected. It can lead to weight loss and malnutrition.
  • Aspiration pneumonia: When you can’t swallow well, you’re more likely to breathe food or liquid (including saliva) into your lungs. This can cause pneumonia.
  • Breathing problems: If your chest muscles are affected, you could have shortness of breath, or, at worst, respiratory failure.

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Prognosis for Polymyositis

The prognosis for polymyositis depends on how severe a case you have. Most people respond to treatment and get some of their muscle strength back. Some weakness may remain, and your symptoms could come back. While the condition is rarely life-threatening, you could wind up disabled if you don’t respond to treatment. Polymyositis also raises your risk for an autoimmune condition, cancer, or osteoporosis.

WebMD Medical Reference Reviewed by Jennifer Robinson, MD on April 07, 2019

Sources

SOURCES:

Arthritis Foundation: “Myositis.”

Muscular Dystrophy Association: “Polymyositis."

National Institute of Neurological Disorders and Stroke. “NINDS polymyositis information page.”

National Organization for Rare Diseases: “Polymyositis.”

Myositis Association: “Polymyositis,” “Practical concerns” and “Patients living with myositis.”

Mayo Clinic: “Polymyositis.”

Genetic and Rare Diseases Information Center: “Polymyositis.”

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