cardiac involvement. Inflammatory myopathies consist of polymyositis, dermatomyositis, inclusion body myositis, and immune-mediated necrotizing myopathy. Immune-mediated necrotizing myopathy is divided into three subtypes that are fundamentally distinct. Anti-SRP, anti-HMGCR, and autoantibody-negative necrotizing myopathy. Anti-HMGCR is most commonly triggered by pharmacologic statin exposure, but can also be due to exposure to statins from edible mushrooms and yeast extracts. Autoantibody-negative necrotizing myopathy is likely a group of necrotizing myopathies in which the autoantibodies have yet to be discovered. Extramuscular inflammatory features, such as rash arthritis, Raynaud's interstitial lung disease, and myocarditis is uncommon, but most associated with anti-SRP. Our case is about a 45-year-old male with hypertension, hepatitis B, and obesity who was admitted to inpatient rehab with a newly diagnosed autoantibody-negative necrotizing myopathy. He initially presented with a six-month history of progressive symmetric proximal muscle weakness with dysphagia and a 100-pound weight loss. Laboratory evaluation showed an elevated ALT at 189, AST at 216, and CK at 8263. Creatinine kinase levels reflect disease activity and degree of necrosis. Additionally, echocardiogram showed a normal systolic function, but with posterior wall hypokinesis and a small periocardial effusion. He did not undergo further cardiac evaluation at this time. EMG showed abnormal spontaneous activity, diffuse complex repetitive discharges, and short-duration small amplitude motor unit action potentials consistent with an irritable myopathy. A left biceps biopsy showed scattered necrotic and regenerating fibers. He was started on IVIG and solumedrol and discharged to inpatient rehab with oral prednisone and mycophenolate, where he showed improvements in muscle strength. Unfortunately, while at rehab, when he was working with physical therapy, he developed new onset palpitations. An EKG was obtained, which showed new trifascicular block seen in image one. Cardiology was consulted and recommended re-admission to acute care for further evaluation. Telemetry showed frequent runs of non-sustained ventricular tachycardia. Cardiac MRI showed a reduced left ventricular ejection fraction with patchy fibrosis and edema, suggestive of myocarditis. An endomyocardial biopsy showed areas of fibrosis. He underwent an electrophysiologic heart study, which was negative for an inducible ventricular tachycardia fibrillation and ICD placement was deferred. He was again treated with high dose IV glucocorticoids and discharged back to inpatient rehab on metoprolol, IVIG, prednisone, and an increased dose of mycophenolate. He was able to be discharged home from rehab with improvements in muscle strength and FEM scores. Unfortunately, three months later, he had a sudden unexplained death at home that was presumed to be due to a cardiac arrhythmia. This patient developed myocarditis despite improvement in peripheral muscle strength. Routine evaluation for cardiac involvement is recommended in anti-SRP, but has not been recommended in autoantibody negative necrotizing myopathy. Additionally, the appropriate screening tools have not been evaluated, but some studies suggest testing cardiac-specific troponin, EKG, and echo. Abnormalities on these would warrant further evaluation with a cardiac MRI and if indicated, a heart biopsy. Additionally, there are no guidelines for appropriate malignancy screening, but exam, chest and abdominal imaging and appropriate screening tests are recommended for anti-SRP and autoantibody negative immune necrotizing myopathy. Treatment should be with high-dose corticosteroids and adding IVIG if severe, and then within one month adding methotrexate, IVIG, or rituximab. And then maintenance therapy should be with a steroid taper once maximum benefit has been achieved and continued disease-modifying agents for at least two years of well-controlled disease. This case demonstrates cardiac manifestations in autoantibody necrotizing myopathy and warrants if further testing should be done on admission.

autoantibody-negative necrotizing myopathy

inflammatory myopathy

muscle weakness

cardiac involvement

myocarditis