ICD-11 classes
08 Diseases of the nervous system
Diseases of neuromuscular junction or muscle
Primary disorders of muscles
4A41 — Idiopathic inflammatory myopathy
4A41.1 — Polymyositis

ICD-11 4A41.1 — Polymyositis

Polymyositis is an inflammatory muscle disease of unknown aetiology occurring predominantly in adults and characterised clinically by proximal muscle weakness (shoulders, arms, thighs), often with associated myalgia. Involvement of pharyngeal and oesophageal muscles may result in dysphagia and a risk of aspiration pneumonia. Myocarditis with rhythm disturbances or cardiomyopathy is a rare but serious complication. Polymyositis may be associated with other autoimmune diseases, malignancy or viral infection. Although serum muscle enzyme concentrations and electromyography are usually abnormal, definitive diagnosis requires demonstration of characteristic histological changes, including muscle necrosis, muscle fibre regeneration and diffuse infiltration by CD8+ T lymphocytes, on muscle biopsy.

The diagnosis includes nothing.

The diagnosis excludes nothing.

Diagnosis with code 4A41.1 contains 4 clarifying diagnoses:

  1. 4A41.10 — Juvenile polymyositis
  2. 4A41.11 — Paraneoplastic polymyositis
  3. 4A41.1Y — Other specified polymyositis
  4. 4A41.1Z — Polymyositis, unspecified

The diagnosis is coded elsewhere:

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