Norrie Disease
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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 color, 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 (colored 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.
Source: National Institutes of Health
New findings in norrie disease described from Mayo Clinic
2009 JUN 8 - (NewsRx.com) -- According to a study from the United States, "Mutations in the Norrie Disease gene, Norrie Disease Pseudoglioma (NDP) lead to a phenotypically heterogeneous group of retinopathies. We report a novel mutation in the NDP gene identified in a patient whose clinical presentation was suggestive of unilateral persistent fetal vasculature (PFV)." "Ophthalmic examinations, ocular ultrasounds and sequence analysis of the exons of the NDP gene on peripheral blood DNA were performed. A four-month-old boy was referred to our institution for presumed unilateral retinoblastoma. The clinical and ultrasonographic exams were consistent with PFV and retinal detachment of the left eye as well as retinal fibrovascular changes in the right eye. A vitrectomy of the left eye revealed the absence of a retrolenticular stalk and mutation analysis of the NDP gene of the proband and mother demonstrated a novel missense mutation at codon 66, designated as c. 196G A at the cDNA level and E66K at the protein level," wrote E.P. Aponte and colleagues, Mayo Clinic. The researchers concluded: "We report a novel mutation in the NDP gene in a patient whose presentation demonstrates the phenotypic heterogeneity of NDP-related disorders." Aponte and colleagues published their study in Ophthalmic Genetics (A Novel NDP Mutation in an Infant with Unilateral Persistent Fetal Vasculature and Retinal Vasculopathy. Ophthalmic Genetics, 2009;30(2):99-102). For more information, contact B.G. Mohney, Mayo Clinic, Dept. of Ophthalmology, Mayo Clinic, 200 1st St. SW, Rochester, MN 55905, USA. Publisher contact information for the journal Ophthalmic Genetics is: Taylor & Francis Inc., 325 Chestnut St., Suite 800, Philadelphia, PA 19106, USA. Keywords: United States, Rochester, Cancer, DNA, Genetics, Norrie Disease, Oncology, Ophthalmology, Pseudoglioma, Retinoblastoma, Mayo Clinic. This article was prepared by Clinical Oncology Week editors from staff and other reports. Copyright 2009, Clinical Oncology Week via NewsRx.com.
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