Leber Hereditary Optic Neuropathy Caused by the Rare MT-ND1 m.3394T>C Mutation: A Case With Favorable Visual...

Leber hereditary optic neuropathy (LHON) is an inherited mitochondrial optic neuropathy characterized by acute or subacute painless central visual loss. Most cases are associated with three primary mitochondrial DNA mutations; however, rare variants remain incompletely characterized. Early diagnosis is essential for appropriate management and genetic counseling. We report the case of a 51-year-old Lithuanian woman who presented with painless, progressive central visual loss. Initial neurological and ophthalmological investigations were unremarkable, and corticosteroid therapy was ineffective. Genetic testing revealed a rare homoplasmic m.3394T>C mutation in the MT-ND1 gene. The patient was subsequently treated with idebenone and followed for six years. Following initiation of idebenone therapy, the patient demonstrated gradual and sustained improvement in best-corrected visual acuity, reaching 1.0 in both eyes. Visual fields stabilized, and long-term follow-up showed preserved visual function. Optical coherence tomography revealed persistent but stable structural changes, including retinal nerve fiber layer and ganglion cell layer thinning in the affected eye. This case highlights the potential for favorable long-term visual outcomes in patients with LHON associated with rare mitochondrial variants. It underscores the importance of considering hereditary optic neuropathy in patients with painless visual loss and poor response to corticosteroids. Further studies are needed to clarify genotype-phenotype correlations and treatment responsiveness in rare LHON-associated mutations.