Polymyositis

- disorder of muscle characterised by necrosis of muscle fibers, regeneration and inflammation
- presents with proximal muscle weakness and wasting, muscle pain and tenderness and arthralgia
- also associated with dysphagia due to esophageal spasm
- polymyositis + rash (heliotrope rash, Gottron's papules) = dermatomyositis
- associated with malignancy (esp elderly) 
- raised muscle enzymes (creatinine kinase, aldolase)
- raised ESR, anemia, and positive RF and ANA
- EMG: spontaneous fibrillation
- diagnosis: muscle biopsy
- treatment: prednisolone / immunosuppressives




- Mechanics hand is associated with anti-Jo 1 antibodies and should check for interstitial lung disease