Norrie disease is an X-linked recessive disorder characterized by very early childhood blindness due to degenerative and proliferative changes of the neuroretina. This disease only affects males while female carriers have a normal phenotype. During the first weeks of life, bilateral leucocoria appears as a result of a whitish or yellowish mass of immature retina behind the lens, on which a few vessels and elongated ciliary processes can be seen. The anterior chamber may be narrow.

Norrie disease is associated with microphtalmia, hypoplasic irides, synechia, glaucoma, and cataract. About one third of cases develop bilateral perceptive deafness between the ages of 20 and 30 years. The disorder progresses to atrophy of the eyeball (phtisis) within a few months, causing blindness. Psychomotor retardation is frequent (65%), along with many systemic abnormalities (cardiac, pulmonary, skeletal, genitourinary, and gastrointestinal). There is no treatment for this disease.

Norrie disease is a rare disorder; its exact incidence is unknown. It is not associated with any specific racial or ethnic group.

More than 75 mutations in the NDP gene have been identified in individuals with Norrie disease. In normal situations, the norrin protein (encoded by NDP gene) binds to its receptor frizzled-4 and this complex contribute in the developmental processes that are considered vital for the normal eye development as well as other body systems. Specifically, norrin appears to have vital functions in the specialization of retina cells and the establishment of a blood supply to the retina and the inner ear. In the case of Norrie disease, however, the mutations in the NDP gene affect the ability of the norrin protein to bind with frizzled-4, interfering with the specialization of retinal cells for their unique sensory function. As a result, masses of immature retinal cells accumulate behind the lens. Disruption of norrin's role in the establishment of blood vessels supplying the eye eventually causes damage of some of the tissues.

Since Norrin is also expressed in other systems of the body, the effects of the disorder can be widespread. Specific abnormalities and their severity depend on the type and location of the NDP gene mutation. Mutations that delete portions of the NDP gene prevent production of norrin and result in severe problems affecting the eyes and many body systems. Mutations that delete or change single amino acids usually result in less widespread effects.