[A literature review of Norrie disease]

Norrie disease is a rare genetic disorder characterized by bilateral congenital blindness. The salient clinical feature early in life is a dense, white, vascularized mass behind each lens due to maldeveloped retina. Cataracts and corneal opacities are developed in young childhood, followed by bulbar atrophies. Histopathologic examination suggests primary vitreoretinal dysplasia because of developmental arrest of the retina in the middle embryonic stage. Occasional patients show psychomotor retardation or progressive hearing loss as part of a multisystem disorder. The disease is transmitted by an X-linked recessive form of inheritance, with sons of female carriers having a 50% risk for expressing the disease. In recent years, a candidate gene for Norrie disease has been isolated and characterized, which encompasses 27 kilobases and consists of three exons interspersed by two introns. Microdeletions and a variety of point mutations in the disease gene were identified in Norrie patients, although the genotype-phenotype correlation remains to be defined, and molecular diagnosis is now available for Norrie disease. The encoded protein has homology to a protein domain involving mucins and TGF beta, which may play an essential role in targeting of retinal/neural connections.