Sudden bilateral vision loss in a child with LYRM7-related leukoencephalopathy.

A 4-year-old boy presented with poor vision following an episode of febrile illness with abdominal distension, seizures, and respiratory distress with metabolic acidosis. He had bilateral partial optic atrophy. Neuroimaging revealed bilateral symmetric post-contrast enhancement of the optic nerves, diffuse white matter T2-hyperintensities, and a lactate peak on magnetic resonance spectroscopy. Serology for aquaporin-4 and myelin-oligodendrocyte antibodies were negative. Whole exome sequencing showed a homozygous pathogenic variant in the LYRM7 gene (c.2T>C) known to cause mitochondrial complex III deficiency. Following initiation of mitochondrial cocktail therapy, his visual behavior improved.