MERRF is a mitochondrial encephalomyopathy that is clinically characterized by myoclonic epilepsy in association with other features common to mitochondrial encephalomyopathy, such as muscle weakness, cerebellar ataxia, mental retardation, hearing difficulty, and cardiomyopathy. Approximately 80% of patients show the tRNA8344A>G mutation. Patients with phenotypes showing both MERRF and MELAS have been reported, including a patient with the mutation m.3291T>C (Keilland, 2016). Patients with Ekbom syndrome develop lipomas associated with MERRF.
Histopathological findings in muscle tissue obtained from patients with MERRF include RRF and fibers with low COX activity. RRF with preserved COX activity may also be present.
