Myositis

Written by Matthew Hoffman, MD, Nicole Schmidt
Medically Reviewed by Poonam Sachdev on May 01, 2025
10 min read

Myositis refers to a group of conditions that cause inflammation in muscles, but it can also refer to the muscle inflammation itself. This inflammation often leads to weakness, swelling, and pain over time, making it harder to do everyday activities, such as climbing stairs or reaching over your head. Experts aren’t completely sure what causes myositis, but they think it could be triggered by infection, injury, autoimmune conditions, or drug side effects. There’s no cure, but there are things you can do to ease symptoms. The best way to treat myositis depends on what’s causing it.

There are several types of myositis, and each one affects your muscles a little bit differently. Knowing which type you have can help your doctor find the best way to manage your symptoms. These include: 

Polymyositis

It is an autoimmune disease that causes your immune system to mistakenly attack your muscles. It usually affects several muscles at once, especially the ones near the center of your body, such as your arms, hips, thighs, chest, back, neck, and abdomen. Along with muscle weakness and pain, polymyositis can make it harder to swallow, talk, or even breathe. You might also have fever, fatigue, and stiffness, which can make daily tasks more challenging. Polymyositis is rare, affecting fewer than 25 in 100,000 people each year. You’re more likely to develop it if you already have another autoimmune disease.

Dermatomyositis

It affects both your muscles and your skin. It causes muscle weakness that can interfere with common tasks, but it also brings out skin problems, such as rashes, bumps, and discoloration. The symptoms can be aggressive, and in serious cases, the muscle tissue can start to break down and die — a process called muscle degeneration. This can make it harder to do basic functions such as breathing and swallowing. Dermatomyositis is rare, affecting about 1 in 100,000 people each year.

Sporadic inclusion body myositis

Sporadic inclusion body myositis (IBM) is a degenerative disease that slowly weakens your muscles over time. It usually starts in your limbs, either the legs and feet or the arms, wrists, and fingers. IBM usually isn’t painful, but it can make it harder to grip objects and may cause you to fall or trip more often. Symptoms of IBM usually begin after the age of 50 and get worse over time. Experts aren’t sure what causes the disease.

Necrotizing myopathy

Also called necrotizing autoimmune myopathy or immune-mediated necrotizing myopathy, it is a rare condition where your muscle cells start to die, a process known as necrosis. This leads to muscle weakness, especially in the muscles closest to the center of your body, such as your forearms, thighs, hips, shoulders, neck, and back. Unlike some other forms of myositis, necrotizing myopathy doesn’t usually cause a lot of inflammation. Instead, the muscles themselves are directly damaged and slowly break down over time.

Juvenile myositis

It refers to myositis that affects children under the age of 18. There are several types, but the most common is juvenile dermatomyositis, which causes muscle weakness along with a skin rash. It’s most common to feel muscle weakness in the thighs, upper arms, abdomen, and neck, but the disease can affect organs, too. Even though juvenile myositis is a chronic (long-term) condition, many kids have periods of remission, where their symptoms improve or go away.

Myositis can describe muscle inflammation on its own, or a group of diseases where muscle inflammation is the main problem. While experts aren’t exactly sure what causes these diseases, several factors can trigger inflammation, including:

Inflammatory conditions. Certain conditions that cause inflammation throughout the body may also affect the muscles. Many of these are autoimmune conditions, where the body attacks its own tissues. Some inflammatory conditions that could potentially cause more severe myositis include:

Other inflammatory conditions that tend to cause milder forms of myositis include:

Inflammatory conditions are often the most serious causes of myositis and usually require long-term treatment.

Infection. Viral infections are the most common infectious causes of myositis. Rarely, bacteria, fungi, or other organisms can also trigger it. Viruses or bacteria can attack muscle tissue directly or release substances that damage muscle fibers. Common cold and flu viruses, as well as HIV, are examples of viruses that can cause myositis.

Drugs. Certain medications and drugs can cause temporary muscle damage. If inflammation isn’t an obvious symptom, your doctor may refer to the problem as myopathy — a more general term for diseases that affect your skeletal muscles (myositis, for example, is a type of myopathy). Drugs that can cause myopathy include:

  • Alcohol
  • Alpha-interferon
  • Cocaine
  • Colchicine
  • Plaquenil (hydroxychloroquine)
  • Statins

Muscle problems can happen soon after starting a new medication or after taking it for months or years. Sometimes, the issue is caused by the way two different medications interact. Severe myositis caused by medications is rare.

Injury. Intense exercise can lead to muscle pain, swelling, and weakness that lasts hours or even days after a workout. This kind of inflammation technically counts as a mild form of myositis. Luckily, symptoms almost always go away completely with rest and recovery.

Rhabdomyolysis. This condition occurs when muscles break down quickly, often after a major injury or extreme exercise. It can cause muscle pain, weakness, and swelling. It can also turn your urine dark brown or red. Rhabdomyolysis is a medical emergency that requires attention right away.

 

The main symptom of myositis is muscle weakness, which might be obvious or may only be found with testing. Muscle pain may or may not be present.

In some types of myositis, such as dermatomyositis or polymyositis, muscle weakness typically worsens over weeks or months. It affects large muscle groups on both sides of the body, including the neck, shoulders, hips, and back.

The weakness from myositis can make it harder to move around or stand up. Other symptoms that may be present include:

  • A patchy, red rash, most often on the eyelids, face, neck, or backs of your hands
  • Fatigue
  • Thickening of the skin on the hands
  • Difficulty swallowing
  • Difficulty breathing
  • Weight loss
  • Night sweats

People with myositis caused by a virus usually have symptoms of a viral infection, such as:

However, these symptoms may improve or go away days or weeks before myositis appears.

Most muscle pain is caused by strain injuries or ordinary illnesses, such as colds and flu, not myositis. These types of pains are called myalgias.

If you have any symptoms of myositis, make sure you talk to your doctor. “Warning signs shouldn’t be ignored at any time,” says Ryan Massay, MD, a rheumatologist and clinical assistant professor at the University of Michigan. “I think we all know when something is wrong. You can try to explain it away … but anything that’s out of the ordinary is worth bringing to your doctor.” 

A doctor may suspect myositis based on symptoms such as muscle weakness or other signs of inflammation. To confirm the diagnosis, they might order several tests, including:

Blood tests. High levels of muscle enzymes, such as creatine kinase, may mean there is muscle inflammation. Other myositis blood tests can check for abnormal antibodies that may identify an autoimmune condition.

MRI scan. An MRI scanner uses a powerful magnet and a computer to create detailed images of your muscles. It can help show areas that are inflamed and track changes in the muscles over time.

Electromyography (EMG). During an EMG, a doctor inserts tiny needle electrodes into your muscles to measure how they respond to electrical nerve signals. This test can help spot muscles that are weak or damaged.

Muscle biopsy. This is the most accurate way to diagnose myositis. During the biopsy, your doctor will identify a weak muscle, make a small incision, and remove a tiny sample of muscle tissue for testing. In most cases, a muscle biopsy leads to a clear diagnosis.

Because many conditions can cause muscle weakness and pain, and testing for myositis isn’t always a straightforward process, getting a proper diagnosis can take some time.

The best way to treat myositis depends on what’s causing it.

If it’s due to an inflammatory condition, your doctor might prescribe drugs that suppress the immune system, including:

  • Azathioprine (Imuran)
  • Methotrexate
  • Prednisone

When myositis is caused by infection, it’s most often due to a virus and doesn’t normally need specific treatment. Myositis caused by bacteria (which is uncommon) requires antibiotics to stop the infection from spreading.

Rhabdomyolysis, which is a rare but serious complication of myositis, can lead to permanent kidney damage. People with rhabdomyolysis are usually hospitalized and treated with large amounts of IV fluids.

When myositis is linked to a drug, treatment normally involves stopping the medication. For example, in cases of myositis caused by statin drugs, muscle inflammation usually improves within a few weeks of stopping the medicine.

While there’s no cure for myositis, there are ways to manage your symptoms. Massay says that once you have a diagnosis, taking your medications regularly and attending follow-up appointments with your doctor is extremely important. Your doctor may also recommend working with a physical therapist, who can teach you stretches and exercises to keep the affected muscles flexible and strong. With the right treatment, myositis may go into remission, meaning your symptoms could go away entirely.

“It's important not to suffer in silence,” says Massay. “Be forthcoming with your physicians when you notice that you’re having new symptoms, if you feel like your symptoms are returning, or if you think a particular medication is not working for you.”

Because experts aren’t sure what causes myositis, there’s no way to prevent it. In some cases, people develop myositis after a viral infection, such as a cold or the flu. You can lower your chances of catching a viral illness by:

  • Washing your hands often
  • Avoiding close contact with other people who are sick
  • Keeping your hands away from your eyes, nose, or mouth 
  • Staying up to date on certain vaccines
  • Getting enough sleep
  • Eating healthy
  • Managing your stress

If you’ve been diagnosed with myositis and are taking immunosuppressant drugs, these precautions can help keep you healthy and lower your chances of complications.

Most people with myositis will need to take medication to help manage the condition. Working with a physical therapist can also make a big difference. They can show you stretches and exercises that keep your muscles flexible and strong, which can ease pain and stiffness. While it’s important to stay active, Massay says it’s just as important not to overdo it. “Try not to save the world all in one day because then you just end up crashing,” he says, adding that it’s best to pace your activities and ask for help when you need it.

Massay also recommends the Mediterranean diet. There’s no specific food or diet proven to treat myositis, but eating more anti-inflammatory foods may help lower inflammation. Plus, Massay says that it’s also good for overall health.

Living with myositis can be a big lifestyle change, which might feel difficult to manage or a lot to handle at times. Joining a support group can be a great way to connect with people who understand what you’re going through. Organizations like the Myositis Association provide free online resources, including a community forum. They also organize regional in-person and online meetings. The Myositis Support and Understanding Association also has several free resources, including Facebook groups, Zoom meetings, and an app that offers anonymous, 24/7 support.

Living with myositis can be challenging, and setbacks can happen even when you follow your doctor’s recommendations. “Sometimes, you can do all of the correct things — eat healthy, attend your appointments, take your medication on time — but these diseases are highly unpredictable and they can become uncontrolled,” says Massay. “So just be kind to yourself, give yourself grace, and realize that the road to recovery is long.”

Myositis affects muscles in different ways, and its severity can vary from person to person. While there’s no cure, you can manage symptoms such as weakness, pain, and fatigue through medication, physical therapy, and lifestyle changes. If you have myositis, take your medications as prescribed and see your doctor regularly. Joining a support group can make a big difference by offering emotional support and guidance. If you haven’t been diagnosed but have muscle pain, make sure to talk to your doctor to rule out myositis.

What are the first signs of myositis?

The early signs of myositis often include muscle weakness, pain, and fatigue. Depending on the type, you might also have a patchy, red rash.

What is it like to live with myositis?

Living with myositis can be challenging and may require some big lifestyle changes, but there are treatment options and support that can help you better manage the condition.

What is the life expectancy of someone with myositis?

The life expectancy of someone with myositis depends on the type they have and whether they have other health conditions. For example, someone with inclusion body myositis can expect to live as long as someone without the condition. Dermatomyositis, polymyositis, and necrotizing myopathy are more unpredictable, but 95% of patients are still alive five years after being diagnosed.

Does myositis ever go away?

There’s no cure for myositis, but it can go into remission, which means you may not have any symptoms. 

Do you gain weight with myositis?

If you’re taking steroids as part of your myositis treatment, weight gain can be a side effect.

What organs does myositis affect?

In addition to muscles, skin, and joints, myositis can also affect your lungs, heart, and your intestines (though, the latter is uncommon). 

Is myositis dangerous?

Myositis can be dangerous if it’s left untreated. It’s important to talk to your doctor as soon as you notice symptoms.

Is myositis hereditary​?

It’s not clear what causes myositis, but some experts believe genetics can play a role.