Epidemiology and genetics of Prader-Willi syndrome
- Ann O Scheimann, MD, MBA
Ann O Scheimann, MD, MBA
- Associate Professor of Pediatrics
- Johns Hopkins School of Medicine
- Section Editors
- Mitchell E Geffner, MD
Mitchell E Geffner, MD
- Section Editor — Pediatric Endocrinology
- Professor of Pediatrics
- Keck School of Medicine, University of Southern California
- Melvin B Heyman, MD, MPH
Melvin B Heyman, MD, MPH
- Section Editor — Pediatric Gastroenterology
- Professor of Pediatrics
- University of California, San Francisco
Prader-Willi syndrome (PWS), also known as Prader-Willi-Labhart syndrome, is the most common syndromic form of obesity and is caused by absence of expression of the paternally active genes in a discrete region on the long arm of chromosome 15, either due to deletions from the paternal chromosome or maternal disomy. The vast majority of cases occur sporadically. In adults and children, the primary clinical features are hyperphagia, usually leading to early-onset obesity, hypogonadism, developmental delay, and characteristic facial features. In infants, the most prominent findings are hypotonia and feeding difficulties.
The epidemiology and genetics of PWS will be reviewed here. The clinical features, diagnosis, and approaches to treatment of this disorder are discussed separately. (See "Clinical features, diagnosis, and treatment of Prader-Willi syndrome".)
In 1887, Langdon-Down described the first girl with probable Prader-Willi syndrome (PWS), manifest by mental impairment, short stature, hypogonadism, and obesity; he termed the condition polysarcia . Seventy years later, Prader and colleagues reported a series of patients with similar phenotypes . In 1981, Ledbetter, et al, identified microdeletions within chromosome 15 as the site for PWS .
Prader-Willi syndrome (PWS) is the most common syndromic form of obesity and affects between 350,000 and 400,000 individuals worldwide. Both sexes are affected equally .
Although prevalence estimates differ among studies, this is likely due to using different methods for case identification, and there is no strong evidence for increased risk in specific countries or gene pools. Within the United States, the rate of prevalence has been reported between 1 in 16,062  to 1 in 25,000 . Outside of the United States, reported prevalence rates for PWS range from 1 per 8,000 in rural Sweden  to 1 per 16,000 in Western Japan , 1:15,830 in Australia , and a birth incidence of 1 per 27,000 in Flanders . Within the United Kingdom, a lower population prevalence of 1 in 52,000 was estimated, with a proposed true prevalence of 1 in 45,000 . In each of these populations, PWS represents a very small fraction of children with obesity, or even severe obesity.
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