Polymyositis

Editor-In-Chief: Prab R Tumpati, MD
Obesity, Sleep & Internal medicine
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Polymyositis
Micrograph of polymyositis, showing endomysial inflammation. H&E stain.
Synonyms	N/A
Pronounce	N/A
Specialty	N/A
Symptoms	Muscle weakness, muscle pain, fatigue
Complications	Dysphagia, respiratory failure, cardiac involvement
Onset	Typically between ages 30 and 60
Duration	Chronic
Types	N/A
Causes	Autoimmune disease
Risks	Genetic predisposition, viral infections
Diagnosis	Muscle biopsy, blood tests (e.g., elevated creatine kinase), electromyography
Differential diagnosis	Dermatomyositis, inclusion body myositis, muscular dystrophy
Prevention	N/A
Treatment	Corticosteroids, immunosuppressive drugs, physical therapy
Medication	N/A
Prognosis	Variable; can be managed with treatment
Frequency	Rare
Deaths	N/A

Polymyositis is an inflammatory myopathy characterized by muscle weakness and inflammation. It is classified as an autoimmune disease and primarily affects the skeletal muscles, leading to progressive muscle weakness.

Pathophysiology

Polymyositis is believed to be caused by an immune-mediated process where the body's immune system mistakenly attacks its own muscle fibers. This results in inflammation and degeneration of muscle tissue. The exact cause of this autoimmune response is not fully understood, but it may involve genetic and environmental factors.

Clinical Features

Patients with polymyositis typically present with symmetrical muscle weakness, particularly affecting the proximal muscles such as those of the shoulders, hips, and thighs. This weakness can lead to difficulties in performing everyday activities such as climbing stairs, lifting objects, or rising from a seated position.

Diagnosis

The diagnosis of polymyositis is based on a combination of clinical evaluation, laboratory tests, and muscle biopsy. Elevated levels of muscle enzymes such as creatine kinase (CK) are often found in the blood. Electromyography (EMG) and magnetic resonance imaging (MRI) can also aid in the diagnosis.

Treatment

Treatment for polymyositis typically involves the use of corticosteroids to reduce inflammation. Immunosuppressive drugs such as methotrexate or azathioprine may also be used to manage the condition. Physical therapy is often recommended to maintain muscle strength and function.

Prognosis

The prognosis for individuals with polymyositis varies. With appropriate treatment, many patients experience significant improvement in muscle strength and function. However, some may have persistent weakness or complications such as interstitial lung disease.

See also

• Dermatomyositis
• Inclusion body myositis
• Autoimmune disease
• Myopathy

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