Myositis (polymyositis, dermatomyositis, inclusion ...
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Description

Myositis (polymyositis, dermatomyositis, inclusion body myositis) - Diagnosis and Management Summary

 • Clinical Presentation: 

    - Proximal > distal muscle weakness: difficulty with stairs, standing from seated position, reaching above head

    - Extramuscular: constitutional sx, arthralgias, dysphagia, pulm. sx inc. cough and DOE (ILD), HTN, DM2

    - DM skin findings: heliotrope rash, poikiloderma (chest: V-sign; back: shawl sign; thigh: Holster sign), Gottron’s papules, panniculitis

    - DM sine myositis: skin features w/o muscle weakness, a/w severe ILD (10-20% of DM)

 • Workup: 

    - Abs: +anti-Jo1 (a/w ILD, mechanic hands, arthritis), +anti-Mi2 (15-20%, a/w acute onset, shawl sign, good prognosis), +anti-MDA5

    - Labs: CK, aldolase

    - Muscle biopsy - DM: CD4 cells. PM/IBM: CD8 cells

 • Treatment: 

    - Initiation: prednisone 1mg/kg (up to 100mg/d) x4-6wk, then taper

    - Maintenance: AZA/MTX

    - Resistant/severe: pulse steroids, AZA, MTX, MMF, IVIG, RTX, cyclophosphamide (if ILD)

 • Complications: 

    - (DM) occult malignancy (9-32% incidence): commonly ovarian, breast, colon, lung, NHL, nasopharyngeal cancer

    - Additional: ILD in 10%; upper esophageal involvement; increased risk of MI



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