Angelman syndrome and prenatally diagnosed Prader-Willi syndrome in first cousins.

Prader-Willi syndrome (PWS) and Angelman syndrome (AS) are caused by loss of function of imprinted genes in the 15q11-13 critical region. Reports of PWS and AS in close relatives within the same family are rare. We report on the diagnosis of a familial unbalanced 10;15 translocation causing AS in a child that led to the prenatal diagnosis of an unbalanced 10;15 translocation with resultant deletion of the Prader-Willi critical region in her maternal uncle's offspring.