Crossed VEP asymmetry in a patient with AHR-linked infantile nystagmus and foveal hypoplasia.

Introduction: Infantile nystagmus and foveal hypoplasia associated with AHR gene defects is a newly recognized and rare disorder. Our aim was to present a patient with a novel biallelic AHR pathogenic variant with electrophysiological evidence of chiasmal misrouting.

Materials and methods: Complete ocular examination, fundus imaging, visual evoked potentials (VEP) and full-field electroretinography were performed at initial presentation. Genetic testing was performed by whole exome sequencing.

Results: Female patient of 6 years old presented a reduced best corrected visual acuity, an infantile nystagmus and a grade III typical foveal hypoplasia without ocular hypopigmentation. A crossed asymmetry was discovered on pattern onset/offset VEP. Genetic testing put in evidence a novel homozygous variant in AHR: c.2242del, p. (Gln748Lysfs^*5). During 11-years follow-up period, BCVA gradually improved. There was no evidence of retinal degeneration.

Conclusion: AHR gene defects could be associated with infantile nystagmus, foveal hypoplasia and chiasmal misrouting.