Necrotizing Myopathy Resulting In Myocarditis And Sudden Death

Abstract

AbstractNecrotizing myopathy (NM), a type of idiopathic inflammatory myopathy (IIM), is an autoimmune disorder in which immune cells target skeletal muscle, resulting in muscle breakdown and weakness. Cardiac involvement in this disorder is rare. We highlight a case of autoantibody-negative NM complicated by myocarditis and sudden cardiac death.Case Report: A 45-year-old male with a history of hypertension, previous hepatitis B, and obesity presented with 6 months of progressive proximal lower extremity weakness. Workup revealed elevated creatinine phosphokinase, ESR and CRP, elevated troponin, and electromyography notable for a myopathic process. Age appropriate malignancy screening, infectious workup, and myositis panel were negative. The patient underwent left bicep biopsy which revealed muscle fiber necrosis and regeneration, consistent with the diagnosis of seronegative NM. Patient was discharged on mycophenolate and intravenous immunoglobulin with improvements in peripheral strength. Unfortunately, while recovering, he was readmitted with palpitations and dyspnea. Electrocardiogram showed a new trifascicular block and telemetry revealed frequent runs of non-sustained ventricular tachycardia (NSVT). A Cardiac MRI revealed evidence of myocarditis (Image 1). Endomyocardial biopsy showed fibrosis with entrapped myocytes (Image 2). He was treated with pulse dose intravenous glucocorticoids and mycophenolate was increased. EP study (EPS) was performed which did not reveal inducible VT; therefore, implantable cardiac defibrillator (ICD) was not implanted. Three months later the patient had sudden unexplained death at home.Discussion: Cardiac involvement in IIM—especially seronegative NM—is rare and not well described. Our patient had worsening cardiac involvement despite improvements in his skeletal myopathy. Despite a recent negative EPS, the patient had sudden unexplained death. Perhaps, a lower threshold for ICD implantation should be considered in this population. This case raises awareness for cardiac involvement in seronegative NM and raises the question of whether these patients are at increased risk of sudden cardiac death.