PROS1 and hereditary disease: Norrie disease (ND) is a rare genetic disorder which is X-linked recessive.Norrie disease protein (NDP) gene mutationlocated on the short arm of the X chromosome (Xp11.3) leads to defectivenorrin.[112,113] More than 100 pathogenic variations ofNDP gene have been reported with most common being contiguousdeletions.