Polymyositis: Causes, Symptoms, and Treatment
What Is Polymyositis?
Polymyositis is a type of disease called an inflammatory myopathy, which means that it irritates the muscles that help you move. Polymyositis also damages nearby tissues, such as the blood vessels that supply oxygen and nutrients to your muscles.
It usually affects the muscles in your thighs and upper arms. It causes muscle weakness and pain on both sides of your body and makes it hard to do everyday things, such as climbing stairs and getting out of a chair. There’s no cure for this ongoing (chronic) condition, but there are treatments that can help with symptoms.
Polymyositis vs. dermatomyositis
Polymyositis is related to another inflammatory disease called dermatomyositis. Both conditions cause muscle weakness and soreness, but dermatomyositis also causes a rash. This rash could be smooth or scaly and might not be near the weakened muscles. Dermatomyositis also might lead to swelling around your eyes or fingernails.
Polymyositis vs. polymyalgia rheumatica
Polymyositis shares many symptoms with a condition called polymyalgia rheumatica. These conditions can impact muscles on both sides of your body, particularly near the abdomen. The biggest difference is that polymyalgia rheumatica tends to cause muscle pain and stiffness, but polymyositis causes pain and weakness.
Causes and Risk Factors for Polymyositis
No one knows the exact cause of polymyositis. Research shows that it might be similar to an autoimmune disorder. This is when your immune system, which usually protects you against foreign invaders such as viruses, makes a mistake and attacks your own tissues instead. It might be an inherited condition, which means it's passed down through families.
You are at a higher risk of getting polymyositis if you have an autoimmune condition such as:
- Lupus
- Rheumatoid arthritis
- Scleroderma
- Sjogren’s syndrome
It’s also more common among people with HIV or AIDS.
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.
Polymyositis Symptoms
The symptoms of polymyositis are caused by inflammation (irritation and swelling) in your muscles. The muscle weakness happens on both sides of your body. It usually affects muscle groups closer to the center of your body, such as hips, shoulders, thighs, upper arms, upper back, and neck.