Ophthalmologic findings in a patient with methylmalonic acidemia and the N219Y mutase mutation

We document the clinical ocular presentation of methylmalonic acidemia (MMA) with a mutase defect, specifically the MUT N219Y variant, in a 27-year-old female who presented with sudden bilateral visual acuity deterioration. The ophthalmologic workup included visual acuity testing, biomicroscopic and fundus examinations, macular spectral-domain optical coherence tomography (SD-OCT), fundus autofluorescence, multicolor imaging, retinal nerve fiber layer analysis, kinetic and static visual field testing, and head magnetic resonance imaging. The patient demonstrated bilateral visual acuity loss, more severe in the left eye. SD-OCT of the macula and optic nerve appeared normal, yet static visual field testing showed elevated central threshold values bilaterally, and kinetic testing revealed bilateral constriction. MRI of the head revealed bilateral focal signal abnormalities of the optic nerves, with left-sided predominance. This case represents the first detailed ophthalmologic description in a patient with MMA carrying the MUT N219Y variant.