Severe vision impairment in a patient diagnosed with Leber hereditary optic neuropathy
Introduction. Leber hereditary optic neuropathy (LHON) is one of the most common hereditary optic neuropathies. The three most common mtDNA point mutations are: m.3460G>A MT-ND1, m.11778G>A MT-ND4 and m.14484T>C. The disease causes painless, extreme visual impairment and commonly affects young adult males. Idebenone is the only approved drug for the treatment of LHON. Case Description. A 38-year-old male patient presented with severe visual impairment in both eyes. The time between onset of symptoms and genetic confirmation of the disease was9 years. Visual acuity (Snellen chart, Landolt C optotype) was 0.04 in the right eye and 0.02 in the left eye. Impairment of color vision was also noted. The patient saw 38 and 41 of 135 points in the right and left eyes, respectively, on full-field vision testing. On slit lamp examination, anterior pole findings were within normal limits. Ophthalmoscopy revealed discolored optic nerve disks (OND). Optical coherence tomography of the retinal nerve fiber layer showed severe atrophy. Visual evoked potential testing registered P1 and P2 waves, although a low-amplitude response to stimuli was observed at 10 Hz. Magnetic resonance imaging of the brain was performed but was inconclusive and showed no other causes of OND atrophy. The patient was genetically tested for suspected LHON, and a MT-ND4 gene variantm.11778G>A was found. Idebenone was prescribed, but the treatment showed no effect. Summary. LHON is a maternally inherited genetic disorder associated with mtDNA point mutations. This case report demonstrates the importance of genetic testing in patients with severe vision loss. Conclusions. A homoplasmic pathogenic MT-ND4 gene variant m.11778G>A(p.Arg340His) associated with poor visual outcomes was discovered. The case of our patient confirms this, as treatment with idebenone showed no effect.