Polymyositis is a rare type of myopathy, or muscle disease, that causes inflammation and weakness of the muscles.

People who have polymyositis may experience discomfort, pain, and weakness in several muscles. As the muscle weakness develops, a person may have difficulty moving around as usual or carrying out daily tasks.

There are several different treatment options for polymyositis. Most people respond well to treatment, and some even make a full recovery. However, lifelong treatment is usually necessary to prevent a relapse.

In this article, we discuss the symptoms of polymyositis and the treatment options available. We also explain the outlook for people living with the condition.

a man holding his shoulder because it's sore from polymyositisShare on Pinterest
A person with polymyositis may experience weakness in the muscles closest to the torso.

Polymyositis is a type of muscle myopathy. The term “myopathy” refers to a disease in which the muscle fibers do not function as they should.

Polymyositis causes chronic inflammation and weakness of the skeletal muscles, which are responsible for movement. The condition can affect both sides of the body and usually begins in the muscles of the upper arms and thighs.

Without treatment, polymyositis may eventually lead to difficulties with movement and mobility.

Polymyositis is a rare condition. It typically affects people between the ages of 31 and 60 years, and it is more common among women than men.

The exact cause of polymyositis is unclear. However, the condition shares many similarities with autoimmune diseases.

In an autoimmune disease, the immune system mistakenly attacks healthy tissue in the body. In people with polymyositis, the immune system may attack muscle fibers, causing damage and inflammation.

Some genes may also influence the risk of polymyositis.

The main symptom of polymyositis is muscle weakness. It usually affects the proximal muscles first. These are the muscles closest to the torso. Examples include the:

  • shoulder muscles
  • upper arm muscles
  • hip muscles
  • thigh muscles

As the disease progresses, muscle weakness can also occur in the distal muscles, which are the muscles farthest from the torso. Examples include the calf muscles and forearm muscles.

In the beginning stages, polymyositis may cause mild discomfort. As muscles continue to weaken, a person may begin to experience difficulty moving. Depending on which muscle groups it affects, the condition may lead to difficulties with the following tasks:

  • climbing stairs
  • lifting objects
  • reaching up
  • standing up
  • raising the head when lying down
  • swallowing

Polymyositis can be associated with lung problems, and interstitial lung disease is a possible cause of any breathing problems that occur. Other possible symptoms of polymyositis include:

Dermatomyositis is another form of muscle myopathy. The primary symptom is a patchy red or purple skin rash that occurs either before or during the muscle weakness.

Rashes can occur almost anywhere on the body. However, they typically develop in the following areas:

  • eyelids
  • knuckles
  • elbows
  • heels
  • toes

Dermatomyositis usually appears after people reach their late 40s but before they reach their mid-60s. Unlike polymyositis, which is rare among people below the age of 18 years, dermatomyositis can affect children between 5 and 15 years of age.

To diagnose polymyositis, a doctor will perform a physical examination and assess a person’s medical history. If the doctor suspects polymyositis, they may order one or more of the following tests:

Blood tests

A person who has polymyositis may have high levels of antibodies specific to muscle inflammation or creatine kinase (CK) in the blood.

Antibodies are proteins that the immune system releases as part of the inflammatory process. High levels of antibodies can, therefore, indicate the presence of underlying inflammatory diseases, such as polymyositis.

CK is an enzyme present in muscle fibers. When muscle fibers become damaged, CK leaks out of the fibers and into the bloodstream.

Electromyography test

An electromyography (EMG) test assesses the function of muscles and the nerves that control them.

The test involves inserting a fine needle called an electrode into the muscle. A doctor will then ask the person to contract the muscle. A computer monitor records the electrical activity of the muscle in response to the contraction.

Imaging tests

Imaging tests, such as MRI or ultrasound scans, can help a doctor identify muscle inflammation.

Muscle biopsy

A muscle biopsy involves removing a small amount of muscle tissue for closer examination.

There is no cure for polymyositis. However, treatments are available to help manage the inflammation and alleviate symptoms.

Some potential treatment options include:

  • corticosteroids and anti-inflammatory medications to reduce muscle inflammation
  • immunosuppressant drugs to suppress the immune system and control inflammation
  • intravenous immunoglobulin, which uses healthy antibodies to counteract the antibodies that are damaging the muscles
  • physical therapy to help strengthen the muscles and improve mobility
  • speech therapy to treat associated speech difficulties and disorders

People with polymyositis generally require lifelong treatment. Most people respond well to the treatment and regain strength in their muscles. However, some people may find that their muscle weakness persists to some degree.

Many people who receive treatment for polymyositis partially or completely recover from the disease. However, they may remain at risk of a relapse.

People who do not recover from polymyositis may go on to develop significant disabilities. In rare cases, the condition may lead to additional health complications, such as:

Polymyositis is a type of myopathy that causes muscle inflammation and weakness. Over time, the condition can cause mobility issues and other symptoms.

The cause of polymyositis is not clear. However, the condition shares many similarities with autoimmune diseases that cause excessive and uncontrolled inflammation in the body.

There is currently no cure for polymyositis, but treatment options are available to help manage the inflammation and alleviate symptoms.

Many people who receive treatment for polymyositis make a partial or full recovery, although they may remain at risk of disease relapse.