While some examples have been described for mice and dogs42, 43, 44, 45, 46, the first report in humans dealt with a known AIPL1 mutation p.(Arg302Leu) identified as a potential modifier allele in a patient with Leber congenital amaurosis (LCA) and prominent maculopathy carrying two CRB1 mutations47. The gene discussed is AIPL1; the disease is Leber congenital amaurosis.