Giant Ring Mitochondria in a Patient with Heart Failure and Cerebral White Matter Disease Due to MT-TL1 Mitochondrial Gene Mutation

Abstract Background The presence of giant ring mitochondria on endomyocardial biopsy is rarely reported and does not have a well-defined differential diagnosis. Methods We report the case of a 54-year-old man with heart failure with preserved ejection fraction and left ventricular hypertrophy, initially thought to have an infiltrative cardiomyopathy. Results The patient was found to have extensive vacuolization caused by the presence of giant ring mitochondria on endomyocardial biopsy. Mitochondrial genetic testing revealed an A3243G mutation in the MT-TL1 gene, which is a mitochondrial encoded tRNA-leucine molecule. Conclusions Mitochondrial disease should be considered in patients presenting with unexplained cardiomyopathy and skeletal muscle, cerebral, or metabolic abnormalities. In this case, the presence of unexpected extensive cardiomyocyte vacuolization and giant, ring-shaped mitochondria on endomyocardial biopsy prompted mitochondrial genetic testing, which ultimately resulted in the correct diagnosis and treatment.