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. The gene discussed is IMPG2; the disease is retinal disorder.