Norrie Disease

What is Norrie disease?

Norrie disease is an inherited eye disorder that leads to blindness in male infants at birth or soon after birth. It causes abnormal development of the retina, the layer of sensory cells that detect light and colour, with masses of immature retinal cells accumulating at the back of the eye. As a result, the pupils appear white when light is shone on them, a sign called leukocoria. The irises (coloured portions of the eyes) or the entire eyeballs may shrink and deteriorate during the first months of life, and cataracts (cloudiness in the lens of the eye) may eventually develop.

About one third of individuals with Norrie disease develop progressive hearing loss, and more than half experience developmental delays in motor skills. Other problems may include mild to moderate mental retardation, often with psychosis, and abnormalities that can affect circulation, breathing, digestion, excretion, or reproduction.

How common is Norrie disease?

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

What genes are related to Norrie disease?

Mutations in the NDP gene cause Norrie disease.

The NDP gene produces a protein called norrin, which is believed to be crucial to normal development of the eye and other body systems. In particular, it seems to play a critical role in the specialization of retinal cells for their unique sensory capabilities. It is also involved in the establishment of a blood supply to tissues of the retina and the inner ear.

Mutations in this gene result in a protein that cannot perform its normal functions, thus causing the signs and symptoms of Norrie disease.

How do people inherit Norrie disease?

This condition is inherited in an X-linked recessive pattern. A condition is considered X-linked if the mutated gene that causes the disorder is located on the X chromosome, one of the two sex chromosomes. In males (who have only one X chromosome) one altered copy of the gene in each cell is sufficient to cause the condition. In females (who have two X chromosomes) a mutation must be present in both copies of the gene to cause the disorder. Males are affected by X-linked recessive disorders much more frequently than females. A striking characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.

In X-linked recessive inheritance, a female with one altered copy of the gene in each cell is called a carrier. She can pass on the gene, but generally does not experience signs and symptoms of the disorder. In rare cases, however, carrier females have shown some retinal abnormalities or mild hearing loss associated with Norrie disease.

What other names do people use for Norrie disease?

  • Anderson-Warburg syndrome
  • Atrophia bulborum hereditaria
  • congenital progressive oculo-acoustico-cerebral degeneration
  • Episkopi blindness
  • Fetal iritis syndrome
  • Norrie's disease
  • Norrie syndrome
  • Norrie-Warburg syndrome
  • Oligophrenia microphthalmus
  • pseudoglioma congenita
  • Whitnall-Norman syndrome

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