Diagnostic dilemma: Leber's hereditary optic neuropathy in a 70-year-Old woman.

Purpose: Reports of atypical cases have increased awareness that Leber's hereditary optic neuropathy (LHON) is not solely a disease of young men. Here, we present a case of a 70-year-old woman who presented with bilateral sequential loss of vision, and, after several diagnostic dilemmas, was ultimately found to have LHON. Observations: Our patient presented with a one-month history of progressive central vision loss in the right eye. Her visual acuities were 20/200-1 and 20/25-2. She had no afferent pupillary defect and intraocular pressures were normal. Fundus examination revealed cup-to-disc ratios of 0.9 and 0.7 with an inferior notch on the right. Visual fields showed superior arcuate and cecocentral depressions on the right and an inferior nasal step on the left. Ocular coherence tomography showed bilateral, superior and inferior retinal nerve fiber layer thinning. She was diagnosed with normal-tension glaucoma. Laboratory studies and neuroimaging were unremarkable. One month later, she presented with new central vision loss in the left eye. Ocular coherence tomography revealed new, mild optic nerve swelling in the left eye. Due to concern for an acute-on-chronic process, she was hospitalized and treated with intravenous steroids and later plasmapheresis with modest improvement. An extensive laboratory evaluation, lumbar puncture, temporal artery biopsy, and PET CT were normal. Mitochondrial genetic testing was ordered. After a six-week delay, the results revealed a pathogenic variant at mitochondrial position 11778, consistent with a diagnosis of LHON. She began treatment with idebenone. At the most recent visit, her vision had improved to 20/40 and 20/30. Conclusions and importance: LHON is typically not part of the initial differential diagnosis of an optic neuropathy in patients outside the typical demographic. As genetic testing has become more widely available, clinicians should consider including LHON in their differential diagnosis of any optic neuropathy, especially if other, more common causes have been ruled out.