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
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Reports outline ophthalmology in children study findings from William Beaumont Hospital
2007 MAR 1 -- A new study, "Retinal phenotype-genotype correlation of pediatric patients expressing mutations in the Norrie disease gene," is now available. In this recently published article, scientists in the United States conducted a study "To correlate the ophthalmic findings of patients with pediatric vitreoretinopathies with mutations occurring in the Norrie disease gene (NDP). One hundred nine subjects with diverse pediatric vitreoretinopathies and 54 control subjects were enrolled in the study." "Diagnoses were based on retinal findings at each patient's first examination. Samples of DNA from each patient underwent polymerase chain reaction amplification and direct sequencing of the NDP gene. Eleven male patients expressing mutations in the NDP gene were identified in the test group, whereas the controls demonstrated wild-type NDP. All patients diagnosed as having Norrie disease had mutations in the NDP gene. Four of the patients with Norrie disease had mutations involving a cysteine residue in the cysteine-knot motif. Four patients diagnosed as having familial exudative vitreoretinopathy were found to have noncysteine mutations," wrote W.C. Wu and colleagues, William Beaumont Hospital. The researchers concluded: "One patient with retinopathy of prematurity had a 14-base deletion in the 5' untranslated region (exon 1), and 1 patient with bilateral persistent fetal vasculature syndrome expressed a noncysteine mutation in the second exon. Mutations disrupting the cysteine-knot motif corresponded to severe retinal dysgenesis, whereas patients with noncysteine mutations had varying degrees of avascular peripheral retina, extraretinal vasculature, and subretinal exudate. Patients exhibiting severe retinal dysgenesis should be suspected of carrying a mutation that disrupts the cysteine-knot motif in the NDP gene." Wu and colleagues published their study in Archives of Ophthalmology (Retinal phenotype-genotype correlation of pediatric patients expressing mutations in the Norrie disease gene. Archives of Ophthalmology, 2007;125(2):225-30). For more information, contact W.C. Wu, William Beaumont Hospital, Associated Retinal Consultants, 3535 W 13 Mile Road, Royal Oak, MI 48073 USA. Publisher contact information for the journal Archives of Ophthalmology is: American Medical Association, 515 N State St., Chicago, IL 60610, USA. Keywords: United States, Royal Oak, Ophthalmology, Retinopathy. This article was prepared by Hospital Law Week editors from staff and other reports. Copyright 2007, Hospital Law Week via NewsRx.com.
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