Present a case of Myoclonic Epilepsy with Ragged-Red Fibers (MERRF) Syndrome and highlight variability in clinical presentation of MERRF within a single family of five generations.

MERRF is a rare multisystem mitochondrial syndrome caused by genetic mutations in the mitochondrial DNA. The presentation of MERRF is highly variable among members of the same family. Mutations present with vast phenotypical variability including cerebellar ataxia, progressive muscle weakness, sensorineural deafness, cardiac arrhythmias, cognitive decline, and optic atrophy.

A 53-year-old Ecuadorian female presented with proximal muscle weakness, muscle jerking, and unsteady gait. The symptoms started ten years ago when she experienced intermittent jerks of her right arm, leg, and face followed by progression to muscle weakness and difficulty walking. The patient has a strong family history with many relatives presenting with muscle weakness, myoclonic epilepsy, lipomas, and others dying at young ages and after falls. There is high clinical suspicion that 13 out of 38 family members have MERRF, among which two have been confirmed to have the disease via genetic analysis. 

Examination of the patient revealed low muscle tone, moderate proximal muscle weakness, and a waddling unsteady gait. Creatinine phosphokinase was elevated at 648 U/L. Electromyography showed non-irritable myopathy of the proximal muscles and chronic compensated cervical and lumbar radiculopathy, the nerve conduction study did not reveal neuropathy. Brain MRI was unremarkable. Genetic analysis revealed a pathogenic variant in the MT_TK gene m.8344A>G with 78% heteroplasmy.

This case highlights the multifaceted needs of MERRF, ranging from timely diagnosis, treatment, fall prevention, awareness, and research. Addressing these needs is crucial in improving the quality of life for affected individuals and their families.