Besides genetic alterations, FEVR is differentiated from Norrie disease by its slow progression.8,17 Mutations involving cysteine residues of the NDP gene resulted in Norrie disease, whereas mutations involving the non-cysteine residues were found to be associated with FEVR.28 As well as Norrie disease, persistent fetal vasculature syndrome, which has quite similar phenotypic features with Norrie disease without evidence of inheritance, must be considered in differential diagnosis. The gene discussed is NDP; the disease is Norrie disease.