Our data support Birtel et al.’s proposal of haploinsufficiency as a potential mechanism in IMPG2 retinopathy as 4/5 of our IMPG2 maculopathy patients were heterozygous for a truncating variant and all six patients with RP had at least one truncating variant, of which three had two truncating variants. This evidence concerns the gene IMPG2 and retinitis pigmentosa 1.