A group of 33 patients was selected from those referred for genetic testing at the North West Thames Regional Genetics Service, based at Northwick Park Hospital in Harrow, UK, with approval from the Harrow Research Ethics Committee. Inclusion was based on 3 criteria: mental retardation; dysmorphology; and weight >97th percentile for age and gender. Abnormal karyotype, Fragile X and Prader Willi Syndrome were previously excluded.
