A novel homozygous nonsense variant in CABP4 causing stationary cone/rod synaptic dysfunction.

Introduction: Variants in the CABP4 gene cause a phenotype to be included in the spectrum of congenital stationary night blindness, though some reports suggest that the clinical abnormalities are more accurately categorized as a synaptic disease of the cones and rods. We report a novel homozygous nonsense variant in CABP4 in a patient complaining of non-progressive reduced visual acuity and photophobia but not nyctalopia.

Methods: Complete ocular examination, fundus photographs, autofluorescence, optical coherence tomography, electroretinography, and targeted sequencing of known inherited retinal disease-associated genes.

Results: A 25-year-old man monitored for 13 years complains of a lifelong history of stable reduced visual acuity (20/150), impaired color vision (1 of 14 plates), small-amplitude nystagmus, and photophobia without nyctalopia. He is also hyperopic (+7D), and his electroretinography shows significantly reduced rod and cone responses. Targeted genetic analysis revealed a novel homozygous variant in the CABP4 gene at c.181C>T, p. (Gln61*) underlying his clinical presentation.

Conclusions: A novel variant in CABP4 is associated with stationary cone and rod dysfunction resulting in decreased acuity, color deficit, and photophobia, but not nyctalopia.