Info
inflammatory myopathies
- Definition and epidemiology (NEJM 2015;372:1734; Lancet Neurol 2018;17:816)
- Clinical manifestations
- Diagnostic studies (Ann Rheum Dis 2017;76:1955)
- ↑ CK (rarely >100,000 U/L, can be ↑↑↑ in NM), aldolase, SGOT, LDH; ± ↑ ESR & CRP
- Autoantibodies : ⊕ ANA (>75%)
- Consider EMG (↑ spontaneous activity, ↓ amplitude, polyphasic potentials w/ contraction) or MRI (muscle edema, inflammation, atrophy) for evaluation; may guide biopsy
- Pathology and muscle biopsy
- ↑ CK (rarely >100,000 U/L, can be ↑↑↑ in NM), aldolase, SGOT, LDH; ± ↑ ESR & CRP
Treatment (Nat Rev Rheum 2018;14:279)
- Immunosuppression not effective for IBM. For all others:
- Steroids (prednisone 1 mg/kg); MTX or AZA early if mod/severe or taper fails (2-3 mo)
- For resistant (30-40%) or severe disease: AZA/MTX combo, IVIg (NM, DM ± PM), rituximab, MMF, cyclophosphamide (esp. if ILD or vasculitis)
- IVIg w/ pulse steroids acutely for life-threatening esophageal or resp muscle involvement
- ✓ for occult malignancy (esp. if DM); monitor respiratory muscle strength with spirometry
- NM: stop statin; steroids + MTX, RTX, or IVIg