Myoclonic Epilepsy With Ragged Red Fiber Cardiomyopathy: A Case Report and Brief Review of Literature.

Myoclonic epilepsy with ragged red fibers (MERRF) is a rare mitochondrial disease that can affect various organs, including the heart. We present a case report and brief review of the literature with the aim of exploring the progression of cardiac involvement in patients with MERRF. A 65-year-old male with a history of MERRF, first diagnosed at age 55 with interventricular septum hypertrophy, presented with acute heart failure. The patient's clinical course over 10 years demonstrated a transition from a hypertrophic to a dilated cardiomyopathy phenotype, contrasting earlier findings suggesting rapid progression in younger patients. Despite optimized heart failure therapy, the patient experienced a progressive decline in ventricular function with frequent ventricular arrhythmias, ultimately requiring implantable cardioverter-defibrillator (ICD) placement. This case supports the hypothesis that MERRF-related cardiac involvement may progress more slowly when onset occurs later in life, leading to a gradual transition from hypertrophic to dilated cardiomyopathy. An accurate cardiac diagnostic workup is essential for early detection and timely intervention in such patients. The natural history of cardiac involvement in MERRF can vary significantly based on the age of onset, highlighting the importance of personalized diagnostic and therapeutic approaches in managing this rare mitochondrial disorder.