Norrie disease is caused by a change (mutation) in the NDP gene, which is located on the X chromosome. It is inherited in an X-linked recessive manner. The NDP gene provides instructions for making a protein called norrin, which affects the way cells and tissues develop. In particular, the norrin protein seems to play an important role in the development of retinal cells in the eye. It is also involved in creating a blood supply to tissues of the retina and the inner ear, and the development of other body systems. Mutations in the NDP gene can prevent the norrin protein from working correctly, resulting in the signs and symptoms of Norrie disease.
Last updated: 3/11/2016
What causes autism spectrum disorders (ASD)?
There is no known single cause of autism spectrum disorders, but it is generally accepted that ASD is caused by abnormalities in brain structure or function. Brain scans often show differences in the shape and structure of the brain in children with ASD versus children without ASD. Researchers are investigating a number of theories, including the link between heredity, genetics, and medical problems. In many families, there appears to be a pattern of autism or related disabilities, further supporting a genetic basis to the disorder. While no one gene has been identified as causing ASD, researchers are searching for genetic material that children with ASD may have inherited. It also appears that some children are born with a susceptibility to ASD, but researchers have not yet identified a single "trigger" that causes autism to develop.
Currently a genetic cause can be identified in 20% to 25% of children with ASD. The cause of autism in the remaining 75% to 80% remains unknown.
A small number of cases can be traced to specific exposures during pregnancy. However, it remains unclear whether those who develop autism after such an exposure are also genetically predisposed to develop ASD. The search for other environmental causes of ASD has centered primarily on childhood immunizations given around the time that ASD is recognized; however, no scientific evidence for a relationship between vaccines and autism has been identified.
Last updated: 6/10/2016
Is the X chromosome associated with autism?
Certain genes on the X chromosome (known as X-linked genes) may play a role in the development of autism spectrum disorders, as several genetic disorders caused by changes in genes on this chromosome share the features of autism. Increasing evidence suggests that genetic influences from the X chromosome play a crucial role in the fact that many more males than females have autism.
Researchers have noted that it is difficult to identify a clear relationship between the influence of any single gene (out of several potential candidates) and any aspect of the signs of autism spectrum disorders. Many experts believe that there are probably other important influences that could be environmental in origin.
Last updated: 11/30/2010
Is there a relationship between Norrie disease and autism?
We were not able to locate any reported cases of individuals diagnosed with both Norrie disease and autism. However, approximately 30-50% of males with Norrie disease have developmental delay, intellectual disability, behavioral abnormalities, or psychosis. These features have also been observed in some individuals with autism.
Last updated: 11/30/2010
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