Phenotypes and genotypes underlying paradoxical pupillary reaction in children.

Paradoxical pupillary reaction (initial pupillary constriction to darkness) has been most associated with the inherited retinal disorders congenital stationary night blindness and achromatopsia. However, underlying genotypes and associations with other pediatric retinal phenotypes are not well documented. A retrospective review for paradoxical pupillary reaction was performed at the Ocular Genetics Clinic of Cleveland Clinic Abu Dhabi (2016-2020). Four children from 4 different families were identified, all of whom had had genetic confirmation of the clinical diagnosis. Associated pathogenic variants were in TRPM1 (biallelic; two boys; congenital stationary night blindness), CABP4 (biallelic; one boy, congenital cone-rod synaptic disorder) and PAX2 (monoallelic; one girl, papillorenal syndrome). Genetically confirmed affected relatives of the 2 probands with TRPM1-related congenital stationary night blindness did not show the phenomenon. This study documents novel genotypes and phenotypes that can be associated with paradoxical pupillary reaction in children and confirms potential intrafamilial variable expressivity for the phenomenon.