Prader-Willi syndrome (PWS) is a genetic developmental disorder with a unique set of medical, cognitive, and behavioral characteristics. First recognized as a "syndrome" in 1956 by Prader, Labhart, and Willi, PWS is now recognized as one of the most common microdeletion syndromes and genetic causes of obesity. Over the last 25 years, many children and adults have been diagnosed with this complex, genetic developmental disorder.
Prader-Willi syndrome is caused by abnormalities of the imprinted region of proximal 15q, resulting in the absence of the normally active paternal gene in the region. This absence can be caused by either a paternal interstitial deletion, a maternal uniparental disomy, or a mutation or other abnormality in the imprinting process. The most common way of genetically diagnosing Prader-Willi syndrome is a procedure called methylation. To detect the specific cause of the microdeletion, flourescent in situ hybridization (FISH) is used. PWS affects boys and girls equally regardless of race. Approximately 1 in 10,000 to 15,000 individuals are affected by Prader-Willi syndrome.
Individuals with PWS may experience other health problems:
Individuals with PWS experience a range of cognitive deficits and behavioral problems:
To learn more about PWS, go to the Gene Clinics profile page.
Williams syndrome (WS) is a genetic developmental disorder that is distinguished by characteristic medical problems, mild to moderate cognitive deficits, and a distinct personality profile. WS was first recognized as a "syndrome" in 1961 by Williams and colleagues in a report on four unrelated individuals with supravalvular aortic stenosis, distinctive facial features, growth retardation, and "mental retardation". Shortly thereafter, researchers reported on other patients who, in addition to the above findings, had other vascular stenoses, dental anomalies, and a friendly personality (Beuren, Apitz, & Harmjanz, 1962). WS affects boys and girls equally regardless of race. Approximately 1 in 20,000 individuals are affected by WS.
Williams Syndrome is caused by a microdeletion involving the elastin gene on the long arm of chromosome 7. This microdeletion is a chance event that occurs during either maternal or paternal gametogenesis. The possibility of parents having another child with WS is quite small. However, a person with WS has a 50% chance of having a child who also has the syndrome. The microdeletion on chromosome 7 can now be detected using a specialized laboratory technique called fluorescent in situ hybridization (FISH). Using this technique, 90% to 98% of all clinically diagnosed cases of Williams Syndrome are confirmed to have the microdeletion. Although there is no known cure for WS, accurate diagnosis is important because the medical and developmental problems associated with WS can be treated or managed.
Throughout their lives, individuals with WS are at risk for developing health problems including:
Some problems are age-related, and a physician caring for someone with WS must be aware of the natural progression of the disorder.
WS is also characterized by a highly unique cognitive, linguistic,
and behavioral profile:
To learn more about WS, go to the Gene Clinics profile page.