NDP and Norrie disease: Norrie disease is associated with loss-of-function mutations in Norrin (NDP) (>100 mutations reported) whereas FEVR is caused by mutations in multiple genes including NDP/FZD4/LRP5/TSPAN12/ZNF408 [124,125,126,127,128] and recently reported CTNNA1 [129] and KIF11 [130].