Myositis: Symptoms, Causes & Treatment

What is myositis?

Myositis is a disease that makes your immune system attack your muscles. It causes chronic inflammation — swelling that comes and goes over a long time. Eventually, this inflammation makes your muscles feel increasingly weak. It can also cause muscle pain.

Myositis is a type of myopathy. Myopathy is a general term that refers to diseases that affect the muscles that connect to your bones (skeletal muscles). Different forms of myositis affect different groups of muscles throughout your body. Myositis usually affects the muscles you use to move, including muscles in your:

• Arms and shoulders.
• Legs and hips.
• Abdomen and spine (your trunk).

Other people with myositis experience muscle weakness on or near their:

Experts aren’t certain what causes myositis, and there’s no cure for it. Your healthcare provider will treat the symptoms you’re experiencing. They’ll also recommend exercises like stretching and physical movements that can help strengthen your affected muscles between episodes of myositis symptoms.

Visit a healthcare provider if you feel weak, have trouble moving or notice new pain or rashes on your skin. Go to the emergency room if you have trouble breathing or swallowing.

What are the types of myositis?

A healthcare provider will diagnose a type of myositis based on your symptoms and the location of your affected muscles. There are a few different forms of myositis, including:

Polymyositis

Polymyositis affects multiple muscles at the same time. It usually causes symptoms in muscles on or near the center of your body.

Polymyositis develops gradually over time. It typically affects adults. Females are twice as likely to develop polymyositis than males.

If you have polymyositis, you might have trouble performing movements you usually can, including:

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

Dermatomyositis

Dermatomyositis is a form of myositis that affects your skin in addition to your muscles.

Some cases take months to develop, but dermatomyositis can develop quickly. The sooner you begin treatment, the more likely it is you can avoid having severe complications.

In rare cases, dermatomyositis can be fatal, especially in the first year after symptoms start. It can also increase your risk of developing certain kinds of cancer.

Anyone can experience dermatomyositis. If it affects children, it’s known as juvenile dermatomyositis.

Inclusion body myositis

Inclusion body myositis is a degenerative muscle disease. It usually affects people older than 50.

Inclusion body myositis causes muscle weakness in your extremities (your hands and your legs below your knees). It can also affect the muscles in your throat that help you swallow. Around 30% of people with inclusion body myositis develop dysphagia (difficulty swallowing).

If you have inclusion body myositis, it might be hard to:

• Use your hands and fingers to do precise tasks like buttoning a shirt.
• Grip something small.
• Walk or stand.
• Swallow.