Can Rheumatoid Arthritis Cause Myositis?

Medically Reviewed on 10/28/2022
Can Rheumatoid Arthritis Cause Myositis?
Myositis can appear as a rare side effect of rheumatoid arthritis.

Myositis or muscle swelling is a group of chronic diseases that can cause muscle weakness and pain. It can be caused by injuries, infections, certain medications, or autoimmune conditions, such as rheumatoid arthritis (RA).

RA affects multiple systems and can manifest itself in various ways. A rare side effect of severe or long-lasting RA is myositis.

Although the concept of muscle involvement in RA is driven by a wide range of causes, including inflammation, drugs, impaired joint flexibility, and a sedentary lifestyle, rheumatoid myositis (RM) is still poorly understood.

What are the common signs and symptoms of myositis?

Myositis or inflammatory myopathies are a rare group of diseases marked by inflamed muscles, which can result in persistent muscle weakness and fatigue. The internal organs, skin, and various muscle groups are susceptible to these chronic conditions.

Although every myositis condition is different and has different symptoms and treatments, they are all marked by persistent muscle inflammation.

Common side effects of this inflammation include:

  • Muscle weakness
  • Fatigue
  • Frequent tripping
  • Leg and foot swelling
  • Musculoskeletal and joint pain

The specific symptoms experienced by each person vary and are strongly influenced by any additional medical conditions of the person. The most popular are:

  • Difficulty standing up from a seated position
  • Difficulty climbing stairs
  • Difficulty lifting the arms
  • Trouble swallowing or breathing
  • Skin rashes
  • Scaly skin patches
  • Hardened lumps under the skin
  • Dry cough
  • Hoarse voice

It might be challenging to do everyday tasks, such as getting up from a chair or walking, due to muscle pain and weakness brought on by myositis. Many people with myositis might require the aid of a cane, walker, or other assistive devices to improve mobility.

What are the possible causes of myositis?

Myositis is caused by a variety of factors according to experts. It is an autoimmune disorder in which the body attacks the muscles. Most cases have no known cause. However, recent studies and research identified potential causes that may trigger myositis, such as:

  • Strenuous exercises
  • Infections
  • Certain medications
  • Illicit drugs
  • Inherited diseases
  • Electrolyte imbalances

There is currently no explanation for how myositis develops, but researchers believe that genetics, along with an environmental trigger, may play a role.

Some autoimmune disorders have been linked to milder myositis symptoms, including:

How is myositis diagnosed?

After reviewing the person’s medical history and conducting a thorough physical examination, myositis could be diagnosed. However, to rule out other conditions and confirm the diagnosis, additional tests could be recommended.

To assess the durability and condition of the affected muscles, a muscle biopsy could be done. These examinations can be used to rule out underlying conditions that might mimic the symptoms of myositis.


The term arthritis refers to stiffness in the joints. See Answer

What are the treatment options for myositis?

The primary goals of myositis treatment are to:

  • Reduce muscle inflammation
  • Limit muscle damage
  • Restore muscle function

Additionally, the skin involvement and other organs affected by the disease process must be addressed. Myositis can be treated with the same or a combination of medications that are used to treat RA.

Treatment options for myositis

  • Corticosteroids
    • Oral prednisone is the most used medication in this class, but intravenous (the dispensing of a drug through a vein) corticosteroids can be used to control the disease quickly during an acute flare.
    • Steroids suppress inflammation in the muscles and other parts of the body, but they must be administered in high doses at first to control the disease.
    • Corticosteroids, when properly administered, improve disease activity in 90 percent of people and could be the only form of therapy required in more than half of all people with myositis. When a response is observed, the dose can be gradually decreased to reduce side effects.
  • Biologic response modifiers, such as tumor necrosis factor (TNF)-blocking drugs
    • Inhibit certain types of white blood cells. Have not been well studied but are reported to produce impressive results in a small number of people.
    • Target specific parts of the immune system thought to be involved in myositis.
    • Are widely used to treat rheumatoid arthritis and other rheumatic diseases. However, these are considered experimental medications to treat myositis until better evidence establishing their role to treat myositis is available.

Although these therapies help reduce muscle inflammation and damage, physical therapy for muscle strengthening is well-tolerated and effective in people with myositis. In some ways, the medications can be thought of as ways to limit muscle damage and exercise strengthens the remaining muscle tissue. Muscle strengthening produces beneficial effects even in people with early active disease when performed under the supervision of a skilled therapist.

Medically Reviewed on 10/28/2022
Image Source: iStock image

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