What Is Polymyositis? Symptoms, Diagnosis, and Treatment

If you’ve read our overview of myositis, you know it comes in several forms. Polymyositis (PM) is one of them. While it’s rare, understanding it can help you ask better questions, recognize your symptoms, and feel more prepared at your next doctor’s appointment.

What Is Polymyositis?

Polymyositis is a type of inflammatory muscle disease. The name breaks down simply: “poly” means many, and “myositis” means muscle inflammation. So polymyositis causes inflammation in multiple muscles throughout the body.

It’s an autoimmune condition, which means your immune system (the part of your body that normally fights off illness) mistakenly attacks your own muscle tissue. Over time, that attack causes muscle damage and weakness.

Polymyositis most often affects adults between the ages of 30 and 60, and it’s more common in women than in men.

Polymyositis Symptoms

The most common symptom of polymyositis is muscle weakness, especially in the muscles closest to the center of your body, like your hips, thighs, shoulders, and upper arms. Both sides of the body are usually affected equally.

You might notice that everyday tasks have become harder, like:

• Getting up from a chair or out of the car
• Climbing stairs
• Lifting your arms above your head, such as washing your hair or reaching for a shelf
• Carrying groceries or lifting objects

Some people also experience:

• Fatigue: a deep tiredness that doesn’t go away with rest
• Muscle pain or tenderness: weakness tends to be more noticeable than pain, but both can occur
• Difficulty swallowing: when throat muscles are affected, eating and drinking can become uncomfortable or unsafe
• Shortness of breath: this can happen if breathing muscles are involved, or if the lungs are affected by a complication called interstitial lung disease
• Joint pain or stiffness

Symptoms usually develop gradually over weeks or months. For some people, they appear more suddenly.

Polymyositis vs. Dermatomyositis: What’s the Difference?

Polymyositis and dermatomyositis (DM) look similar in many ways, as both cause muscle weakness in the same areas of the body. The key difference is that dermatomyositis also causes a skin rash, while polymyositis does not.

If you have muscle weakness without a rash, your doctor may consider polymyositis as a possible diagnosis.

What Causes Polymyositis?

Researchers don’t yet know exactly what triggers polymyositis. Like many autoimmune conditions, it’s likely a combination of factors:

• Genetics: Some people may have a higher chance of developing autoimmune disease based on their family history
• Environmental triggers: Infections or other outside factors may prompt the immune system to react in a way that leads to muscle inflammation
• You’re more likely to develop polymyositis if you have another autoimmune disease such as lupus, rheumatoid arthritis, or scleroderma.

Polymyositis is not contagious, and it’s not caused by anything you did or didn’t do.

How Is Polymyositis Diagnosed?

Polymyositis can be difficult to diagnose. Muscle weakness and fatigue are symptoms of many conditions, and because PM is rare, not every doctor has experience recognizing it. It’s sometimes mistaken for fibromyalgia or other muscle and nerve disorders.

To reach a diagnosis, your doctor will likely use a combination of:

• Blood tests: Elevated levels of a muscle enzyme called creatine kinase (CK) can signal muscle damage. Your doctor may also test for proteins called myositis-specific autoantibodies, which can help confirm PM and offer clues about your prognosis and risk of complications
• Electromyogram (EMG): This test measures electrical activity in your muscles to see how well they’re functioning
• MRI: Imaging can reveal areas of muscle inflammation or damage and help your doctor decide where to biopsy
• Muscle biopsy: A small sample of muscle tissue is examined under a microscope. In polymyositis, inflammation appears inside the muscle fiber bundles, a pattern that helps confirm the diagnosis and distinguish PM from other myositis subtypes

Most people are referred to a rheumatologist, a doctor who specializes in autoimmune and inflammatory conditions, for diagnosis and ongoing care.

How Is Polymyositis Treated?

There is no FDA-approved treatment specifically for polymyositis yet, but several medications can reduce inflammation, slow muscle damage, and help improve your strength.

Corticosteroids like prednisone are typically the first line of treatment. They work relatively quickly to reduce inflammation, but they’re often prescribed in high doses for many months. This can cause side effects like bone loss, weight gain, blood sugar changes, and mood shifts. Your doctor will work to lower your dose over time to reduce those risks.

Because of steroid side effects, they’re often used alongside immunosuppressant medications that help calm the immune system. These may include:

• Methotrexate
• Azathioprine
• Mycophenolate mofetil

For people whose polymyositis doesn’t respond to these treatments, doctors may use biologic medications off-label. This means a drug approved for a different condition is used here based on clinical experience and evidence.

IVIg (intravenous immunoglobulin) is another option sometimes used in polymyositis, though it currently has FDA approval only for dermatomyositis. Research and clinical trials are ongoing, and new treatment options are being studied.

Exercise and Physical Therapy for Polymyositis

Exercise is an important part of managing polymyositis, even if it feels counterintuitive when your muscles are already weak or painful. Research shows that carefully guided physical activity can improve muscle strength, reduce fatigue, and help you maintain your independence.

Working with a physical therapist who understands inflammatory muscle disease can help you build a routine that’s safe for your current level of ability. Low-impact options like water exercise, gentle yoga, and walking tend to work well for many people with PM.

The goal is to stay active without pushing yourself to the point of exhaustion. On harder days, it’s okay to dial back. Listening to your body is part of the process.

Living with Polymyositis: What to Expect

Polymyositis affects everyone differently, and it’s hard to predict exactly how it will progress. With treatment, many people are able to significantly reduce their symptoms and return to most of their daily activities. A small number of people do achieve full remission.

Your care team will likely include a rheumatologist and physical therapist, and possibly other specialists depending on your symptoms. For example, you may work with a pulmonologist if your lungs are affected, or a gastroenterologist if swallowing is a concern.

You don’t have to manage this alone. Connecting with others who have myositis through patient communities, support groups, or organizations like the Myositis Association can make a real difference.

Frequently Asked Questions About Polymyositis

Is polymyositis curable?

There is no cure for polymyositis, but symptoms can often be well managed with treatment. Some people achieve remission, meaning their symptoms become minimal or go away for a period of time.

Is polymyositis the same as fibromyalgia?

No. Both conditions can cause muscle pain and fatigue, but they’re different. Fibromyalgia typically does not cause true muscle weakness; your muscles may hurt, but they test as normal in strength. In polymyositis, there is measurable muscle weakness and evidence of inflammation.

Who gets polymyositis?

Polymyositis most commonly affects women between the ages of 30 and 60, though anyone can develop it.

What doctors treat polymyositis?

A rheumatologist is typically the primary specialist for polymyositis. Depending on your symptoms, you may also work with a physical therapist, pulmonologist, or other specialists.

Can I still exercise if I have polymyositis?

Yes, and in fact, exercise is encouraged. A physical therapist can help you find a routine that’s safe and appropriate for your level of activity.

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