Polymyositis

What is polymyositis?

Polymyositis is a rare autoimmune disease that makes your immune system attack your muscles.

It’s a type of myositis. Myositis causes chronic inflammation in your muscles — swelling that comes and goes over a long time. Eventually, this inflammation makes your muscles feel weak.

If you have polymyositis, you may have inflammation in multiple muscles at the same time. It usually affects the muscles on or near the center of your body, including in your:

• Arms.
• Hips and thighs.
• Chest.
• Back.
• Abdomen.
• Neck.

Experts aren’t certain what causes polymyositis, and there’s no cure for it. A healthcare provider will treat the symptoms you’re experiencing and suggest ways to manage how much they affect your daily routine.

How common is polymyositis?

Polymyositis is rare. Experts estimate that it affects fewer than 25 out of every 100,000 people every year.

What are the symptoms of polymyositis?

The most common polymyositis symptoms include:

• Muscle weakness (especially in your shoulders and hips).
• Muscle pain and tenderness.
• Trouble swallowing (dysphagia).
• Difficulty talking.
• Trouble breathing or shortness of breath (dyspnea).
• Fatigue (feeling tired all the time).
• Joint pain.
• Fever.
• Stiffness (especially right after you wake up in the morning).
• Weight loss.

You might have trouble moving or doing activities you usually can, including:

• Standing up after sitting.
• Climbing stairs.
• Lifting objects.
• Reaching over your head.

Some polymyositis symptoms can cause life-threatening complications. Talk to a healthcare provider about which symptoms to look out for. Go to the emergency room or call 911 (or your local emergency services number) if you feel like you can’t breathe or swallow.

What causes polymyositis?

Polymyositis is an autoimmune disease, but experts aren’t sure what causes it. Autoimmune diseases happen when your immune system accidentally attacks your body instead of protecting it.

Polymyositis can start on its own with no cause (idiopathically). Sometimes, other health conditions or reactions to medications trigger it.

You’re more likely to develop polymyositis if you have other autoimmune diseases, including:

• Lupus.
• Rheumatoid arthritis.
• Scleroderma.

Some viral infections can trigger polymyositis, including:

• COVID-19.
• Influenza (the flu).
• The common cold.
• HIV.

What are the risk factors for polymyositis?

Anyone can develop polymyositis, but some groups of people are more likely to, including:

• People assigned female at birth (AFAB). People AFAB are twice as likely to have polymyositis compared to people assigned male at birth (AMAB).
• People living with other autoimmune diseases.
• People 30 to 60 years old. It can develop at any age, but it’s most common in adults in this range.

How is polymyositis diagnosed?

A healthcare provider will diagnose polymyositis with a physical exam and some tests. They’ll ask about your symptoms and examine the muscles that are feeling weak or experiencing symptoms. Your provider will ask you how it feels when you do certain movements or motions.

Your provider will use a few tests to diagnose polymyositis. Some of these tests will rule out other conditions that can cause similar symptoms. Your provider might use:

• Blood tests to look for muscle enzymes or antibodies that show something is damaging your muscles.
• MRI (magnetic resonance imaging) to check for inflammation in your muscles.
• EMG (electromyography) to look for unusual muscle activity.
• A muscle biopsy can show damage and the overall health of your muscle tissue.

How is polymyositis treated?

There’s no cure for polymyositis. Your provider will suggest treatments to manage the inflammation. Treatments can’t make the polymyositis go away, but it can reduce how much symptoms affect your day-to-day life. Many people reach a period of remission (when there’s no inflammation in your affected muscles).

The most common treatments for polymyositis include:

• Corticosteroids: Prescription anti-inflammatory medications.
• Immunosuppressants: Medications that reduce your immune system’s activity and reduce how much it damages your muscles.
• Intravenous immunoglobulin (IVIG): Extra antibodies your provider will inject into one of your veins. IVIG can redirect your immune system so it can’t attack your body’s tissue. IVIG acts like a distraction. If your immune system is focused on going after the IVIG antibodies, it won’t damage your muscles as much.
• Physical therapy: Your provider or a physical therapist will give you stretches and exercises to keep your affected muscles flexible and strong. Physical therapy can strengthen your affected muscles and reduce how much you’re affected by future polymyositis episodes.

Can I prevent polymyositis?

Because experts aren’t sure what causes it, there’s no way to prevent it. We can’t predict who will develop it or when episodes of symptoms will happen or come back.

What can I expect if I have polymyositis?

People usually live with polymyositis for the rest of their lives. There’s no cure for it, but most people find a combination of treatments that helps them put polymyositis into remission.

Some cases of polymyositis cause life-threatening complications. It can be fatal if polymyositis severely affects or damages the muscles in your throat and chest that help you breathe and swallow.

When should I see my healthcare provider?

Visit a healthcare provider right away if you experience new muscle weakness, pain or other symptoms — especially if they don’t get better in a few days.

Talk to your provider if your symptoms get worse or spread. Tell your provider if you feel like your treatments aren’t working as well as they used to, or if it seems like you’re having more (or more severe) polymyositis episodes.

Go to the emergency room or call 911 (or your local emergency services number) if you experience any of the following symptoms:

• You can’t move a part of your body you usually can.
• You’re having trouble breathing.
• You’re having trouble swallowing.

What questions should I ask my healthcare provider?

Questions you may want to ask your provider include:

• Is there a chance I’ll develop another type of myositis, too?
• Which treatments will I need?
• What symptoms or changes should I watch out for?
• How often will I need follow-up appointments to monitor my symptoms or tweak my treatment?

Is polymyositis hereditary?

Some studies have found that polymyositis (and other types of myositis) might have a genetic component. This means that biological parents might pass specific genetic mutations to their children that make them more likely to develop a condition.

However, experts haven’t been able to identify specific genetic mutations that cause polymyositis, and they can’t prove that there’s an increased risk your biological children will develop polymyositis if you have it.

Talk to your healthcare provider about genetic counseling if you’re worried about the risk of passing certain conditions to your biological children.

What is the life expectancy of someone with polymyositis?

Polymyositis won’t usually affect your life expectancy (how long you’ll live). But it can cause fatal complications, especially if it causes severe weakness in your neck and throat muscles. Talk to your healthcare provider if you’re noticing that it’s getting harder to breathe or swallow. They’ll help you adjust your treatments to manage these symptoms before they can cause dangerous complications.

A note from Cleveland Clinic

Polymyositis causes inflammation and weakness in your muscles, usually along the center of your body. You’ll probably have to manage symptoms in periods of episodes that come and go for the rest of your life. There’s no cure for polymyositis, but your healthcare provider will help you find a treatment plan that reduces how much it affects your day-to-day life. Many people are able to put polymyositis into remission and reduce how often they experience symptoms.

Talk to your provider about your risk of severe complications, especially in the muscles that control your swallowing and breathing. They’ll help you understand warning signs to watch out for.