What is polymyositis? causes, symptoms, diagnosis and treatment

What is Polymyositis?

Polymyositis is a rare, chronic inflammatory muscle disease that causes muscle weakness, particularly in the muscles closest to the trunk of the body, such as the shoulders, hips, and thighs. It is classified as an idiopathic inflammatory myopathy (IIM), meaning its exact cause is unknown and it involves immune system-related muscle inflammation.

What is Polymyositis?


Key Features of Polymyositis

  • Symmetrical muscle weakness: Both sides of the body are affected equally.

  • Progressive condition: Symptoms develop slowly over time.

  • Primarily affects adults: Most common between ages 30 and 60.

  • More common in women than in men.

Causes and Risk Factors

The exact cause of polymyositis is unknown, but it is considered an autoimmune disorder, where the body's immune system mistakenly attacks healthy muscle tissue.

Possible triggers include:

  • Viral infections

  • Genetic predisposition

  • Autoimmune reactions

  • Other connective tissue diseases (e.g., lupus, rheumatoid arthritis)

Symptoms of Polymyositis

The hallmark symptom is gradual onset of muscle weakness, especially in:

  • Shoulders and upper arms

  • Hips and thighs

  • Neck and trunk muscles

Other symptoms may include:

  • Fatigue

  • Difficulty climbing stairs or lifting arms

  • Trouble swallowing (dysphagia)

  • Shortness of breath (if respiratory muscles are involved)

  • Low-grade fever or weight loss in some cases

Diagnosis

Diagnosing polymyositis can be challenging and usually involves a combination of the following:

  1. Medical history and physical examination

  2. Blood tests: Elevated muscle enzymes like creatine kinase (CK)

  3. Autoantibody tests: Detect immune system activity

  4. Electromyography (EMG): Measures electrical activity in muscles

  5. MRI of muscles

  6. Muscle biopsy: Confirms muscle inflammation and damage

Treatment of Polymyositis

Although there is no cure, polymyositis can be managed effectively with treatment aimed at reducing inflammation and improving muscle strength.

Main treatments include

  • Corticosteroids: Prednisone is the first-line treatment

  • Immunosuppressants: Methotrexate or azathioprine for steroid-sparing effect

  • Physical therapy: To maintain and regain muscle strength and function

  • IVIG (Intravenous immunoglobulin): For severe or resistant cases

Complications

If untreated or poorly managed, polymyositis can lead to:

  • Muscle atrophy

  • Joint contractures

  • Difficulty swallowing or aspiration pneumonia

  • Lung involvement (interstitial lung disease)

  • Increased risk of certain cancers (in rare cases)

Prognosis

With early diagnosis and proper treatment, many patients experience significant improvement. However, some may have long-term muscle weakness or relapses.

Conclusion

Polymyositis is a serious but treatable autoimmune muscle disease that requires early medical attention and ongoing care. If you or someone you know is experiencing unexplained muscle weakness, especially in the arms or thighs, consult a healthcare provider for evaluation.


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