Myositis and Rheumatoid Arthritis
Although both myositis and rheumatoid arthritis have no known cur, the conditions can be managed through appropriate treatment.

Yes, a person can have both myositis and rheumatoid arthritis (RA) simultaneously. Although myositis can occur in isolation, it may occur with other autoimmune conditions, including RA, systemic lupus erythematosus or scleroderma.

Both RA and myositis have the same basic underlying mechanism for disease causation, the immune system attacking the body’s tissues (autoimmunity). There are, however, distinctive diagnostic criteria to diagnose these conditions as separate entities.

One major difference between RA and myositis is that, unlike RA, myositis is not as damaging to the joints.

What is myositis?

The term myositis refers to a group of conditions that cause muscle inflammation. Myositis belongs to a group of diseases called myopathies. Muscle inflammation or swelling in myositis results in muscle damage and weakness.

  • It is an autoimmune condition, which means that the body’s immune system attacks its tissues to cause inflammation.
  • Like many other autoimmune conditions, myositis is more common in women than in men.
  • This rare disease affects about 50,000 to 75,000 people in the United States.

What are the types of myositis?

Myositis includes a group of idiopathic inflammatory myopathies. The word idiopathic means the exact cause of the disease is not known. It is of five main types. Polymyositis and dermatomyositis are the two most common types of myositis.

  1. Polymyositis: Typically affects muscles on both sides of the body. It can affect several muscles although it usually causes muscle weakness in the hips, thighs, upper arms, shoulders, and neck.
  2. Dermatomyositis: Besides muscle weakness, it affects the skin, causing skin rashes.
  3. Necrotizing myopathy: Characterized by muscle tissue death on lab examination and may need urgent surgical intervention.
  4. Inclusion body myositis: Causes painless muscle weakness. It generally starts after 50 years although it can occur earlier in some cases.
  5. Juvenile forms of myositis: Typically affects children and teens, causing considerable muscle weakness and skin rash.

What causes myositis?

The exact cause of myositis is not well understood. Studies report that inflammation in muscles occurs due to autoimmune attacks. The body’s immune system targets and damages the muscles through an exaggerated inflammatory response.

Certain genes are suggested to play a crucial role to make a person prone to myositis. 

Several factors may trigger myositis, particularly in a genetically predisposed individual, such as:

QUESTION

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

What are the symptoms of myositis?

The symptoms of myositis may vary depending on the type of myositis. The symptoms generally appear gradually although they could be sudden in onset (as in necrotizing autoimmune myositis).

The general myositis symptoms include:

One of the most common types of myositis, dermatomyositis, is characterized by skin rash along with typical myositis symptoms. The rash may appear before, during, or after the onset of muscle weakness.

  • The skin symptoms generally include a red or purple rash that appears in patches.
  • It is typically seen on the face, elbows, chest, back, knees, or toes.
  • The affected person may have photosensitive skin (increased skin sensitivity to light). 
  • Sun exposure may cause hard bumps under the skin due to calcium salts deposition (calcinosis).

In inclusion body myositis affects the fingers and hands, making fine movements difficult, such as buttoning the shirt or grasping things. It may affect the throat muscles, causing dysphagia.

How do doctors diagnose myositis?

The diagnosis of myositis is made by the doctor based on:

  • Your detailed medical history, including a family history of myositis or any autoimmune conditions
  • Physical examination including assessment of gait (walking manner), muscle mass, muscle strength and reflexes, and skin examination
  • Certain tests, such as:
    • Blood tests, including tests to detect autoantibodies in the blood
    • MRI
    • Electromyography
    • Ultrasound
    • Muscle biopsy

How is myositis treated?

Although there is no cure for myositis, the condition can be well managed with appropriate treatment.

Treatment mainly depends on the type and severity of myositis and generally includes:

  • Medications: Generally include corticosteroids, immunosuppressants, and intravenous immunoglobulins.
  • Lifestyle modifications: Include adequate rest, maintaining a healthy weight, avoiding triggers (sun exposure), consuming a healthy diet rich in fruits, nuts, and vegetables, and avoiding alcohol and smoking. Stress management and adequate sleep may help keep away the symptoms.
  • Physical therapy: Exercises and stretches to manage muscle weakness and improve muscle strength and flexibility.

Health Solutions From Our Sponsors

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

Rheumatoid Arthritis. https://understandingmyositis.org/myositis-overlaps/rheumatoid-arthritis/

Inflammatory Myopathies Fact Sheet. https://www.ninds.nih.gov/inflammatory-myopathies-fact-sheet

What Is Myositis? These Are the Signs You Could Have It. https://creakyjoints.org/education/what-is-myositis/