Myoclonic Epilepsy with Ragged-red Fibers with Intranuclear Inclusions.

Area of Science:

• Mitochondrial Genetics
• Neurogenetics
• Rare Diseases

Background:

• Myoclonic epilepsy with ragged-red fibers (MERRF) is a mitochondrial disorder.
• Typical MERRF presents with myoclonus, ataxia, and ragged-red fibers on muscle biopsy.
• Intranuclear inclusions are not a common feature of MERRF.

Observation:

• A 68-year-old woman with MERRF symptoms including optic atrophy and neuropathy presented with p62-positive intranuclear inclusions.
• Genetic analysis excluded known causative genes for intranuclear inclusion diseases.
• A novel variant in the mitochondrial transfer RNA for cysteine (MT-TC) gene was identified.

Findings:

• The novel MT-TC variant was found in a patient with typical MERRF symptoms and the rare finding of intranuclear inclusions.
• The direct association between the MT-TC variant and the presence of intranuclear inclusions remains undetermined.
• This case expands the known genetic landscape of MERRF.

Implications:

• This case suggests that novel MT-TC variants may contribute to MERRF, even with atypical features like intranuclear inclusions.
• Further research is needed to elucidate the role of this MT-TC variant and the mechanism linking it to intranuclear inclusions.
• Clinicians should consider MERRF in patients presenting with myoclonic epilepsy, neuropathy, and optic atrophy, even in the presence of intranuclear inclusions.