NDP and Alzheimer disease: Mutations in the causative genes and the resultant diseases are as follows: NDP gene, X-linked recessive FEVR or Norrie disease; FZD4 gene, AD FEVR; LRP5 gene, both AD and AR FEVR; and TSPAN12, AD FEVR.10,11,12,13,14 The protein products of these genes are involved in the canonical Wnt and Norrin signaling pathways.