A CLINICAL, CYTOGENETIC, AND MOLECULAR STUDY OF 40 ADULTS WITH THE PRADER-WILLI-SYNDROME

A clinical, cytogenetic, and molecular study has been carried out on 4 0 adults with a firm diagnosis of Prader-Willi syndrome. A cytogenetic ally detectable deletion was observed in 58% while further subjects ha d a deletion which was detectable by molecular methods only, giving a total of 76%. Four cases of maternal uniparental disomy (UPD) were all female. Three of them were heterodisomic while the fourth was isodiso mic. Two male probands were heterozygous at all loci tested yet did no t have UPD. Although methylation studies showed that one of them had a single band using probe PW71, the other one had two bands. Psychiatri c studies suggest that females with maternal UPD are indistinguishable psychologically from those with a paternal deletion in 15q11q13.