Norrie disease

Norrie disease is a rare inherited disorder carried on the X chromosome in a recessive pattern, which is why it affects almost only males. It arises from mutations in the gene that makes the growth factor norrin, known as the NDP gene. The main effect is on the eyes: the retina begins to degenerate, often before birth, and the result is blindness at birth or in early infancy, usually by about three months of age. Cataracts, a white pupil reflex, a shrinking eyeball and wasting of the iris can follow. Most affected people also develop progressive hearing loss from vascular abnormalities in the cochlea, beginning in childhood, and a share of them have learning difficulties, delayed development or behavioral problems. More than 400 cases have been described worldwide, and the true prevalence is not known. This entry records what the source states and is not medical advice.