Prader-Willi syndrome in Taiwan.

BACKGROUND: Prader-Willi syndrome (PWS) is a congenital disorder caused by absent expression of paternal genes in 15q11-13 affecting multiple systems. The information concerning the clinical features of this genetic disorder is incomplete in Taiwan.

METHODS: A retrospective analysis was carried out of 70 PWS patients (39 male, 31 females; age range, 1 month-22 years) seen in four major medical centers in Taiwan from January 1980 through June 2005. All cases were confirmed by methylation-specific polymerase chain reaction. The molecular characteristics, birth history, clinical presentation and laboratory studies were analyzed.

RESULTS: Complete genetic analysis was performed in 52 of the 70 patients with PWS. The abnormalities found included deletions in 45 (87%), maternal uniparental disomy (UPD) in five (10%), and a probable imprinting center deletion or an imprinting defect in two (4%). The average weight of the patients at birth was 2588 +/- 540 g. Bone age delay of >2 years and growth hormone (GH) deficiency were noted in 11/40 (28%) and 12/20 (60%), respectively. In the 18 in whom both bone age and GH were assessed, abnormalities of both were found in two (11%). In 2000, Taiwan instituted the Rare Diseases and Orphan Drugs Act and mandated a three-phase screening protocol for PWS. Of the 41 patients diagnosed with PWS before 2000, only four (10%) were diagnosed before the age of 3 months; in the 29 patients diagnosed after 2000, in 15 (52%) the syndrome was confirmed before 3 months of age (P < 0.001).

CONCLUSIONS: The present finding is in contrast to that of most previous reports that indicated a higher incidence of UPD in PWS. It is unclear whether this discrepancy in the incidence of UPD arises from under-diagnosis or because of ethnic differences, a question worthy of further study. The three-phase screening protocol has generated notable improvement in the early diagnosis of PWS in Taiwan.