BACKGROUNDImmune-mediated necrotizing myopathy (IMNM), a systemic autoimmune myopathy, is characterized by its rapid evolution, high levels of creatine phosphokinase (CPK), myofiber necrosis with scarce inflammatory cell infiltrate on muscle biopsy, and involvement of autoantibody, mainly anti-SRP and anti-HMGCR.
CASE REPORTFemale patient, 74 years old, presenting with muscle weakness for five months, predominantly proximal, in lower limbs, symmetric, painless, without fatigability or fluctuation. It progressed with constitutional symptoms, 5 kg loss in 6 months, dysphagia, cutaneous rash in the knees and worsening of the weakness so that she was restricted to the wheelchair in the fourth month of evolution. Past medical history included myocardium infarction two years ago, when she had begun atorvastatin use. In the first medical evaluation, she presented proximal muscle weakness Medical Research Council Scale (MRC) 3 and distal MRC 4, CPK 11718 U/L, elevated liver enzymes (TGO 354 U/L and TGP 344 U/L), positive anti-SRP. She also had signs of acute/subacute myositis and fat deposition in thighs on nuclear magnetic resonance. Serologies, thyroid evaluation, glycated hemoglobin, B 12 vitamin, complete blood count were within the normality, besides negative initial neoplastic screening. Methylprednisolone pulse therapy 1 g/day for 3 days was administered. Initially she progressed with resolution of the skin lesions and of dysphagia, decrement on CPK levels (reaching 2,485 U/L), however maintaining muscle weakness. Pulse therapy was repeated after 3 weeks, 1 g/day for 5 days and azathioprine chosen as immunosuppressive drug. She maintained CPK decrement reaching a nadir of 943 U/L, but persisted with compromised strength and recurred dysphagia for solids after a few days. Intravenous human immunoglobulin was administered and she was discharged home after infusion, with stable muscle strength and improvement of dysphagia.
