Prenatal diagnosis of Prader-Willi syndrome and Angelman syndrome for fetuses with suspicious deletion of chromosomal region 15q11-q13

Objective To identify Prader-Willi syndrome (PWS) and Angelman syndrome (AS) among fetuses with suspicious deletion of the chromosomal region 15q11-q13. Methods In a retrospective study, data were assessed from fetuses missing chromosomal band 15q12 that underwent molecular diagnosis at the National Chen-Kung University Hospital, Tainan, Taiwan, between January 2001 and December 2012. Amniocytes were subjected to molecular testing, including fluorescence in situ hybridization (FISH) analysis, methylation-specific PCR (M-PCR), and methylation-specific multiplex-ligation-dependent probe amplification (MS-MLPA). Results During the 12-year study period, 26 041 amniocyte samples were analyzed at the study center and 27 (0.1%) were found to have a missing 15q12 band. A further 16 samples with a missing 15q12 band were received from other cytogenetic laboratories; as a result, 43 amniocyte samples lacking chromosomal band 15q12 underwent further molecular testing. Among these samples, 3 fetuses (7.0%) were found to have PWS (n = 1) or AS (n = 2). Conclusion A minority of cases with missing 15q12 had deletion of the PWS/AS critical region. This finding draws attention to the subtle structural rearrangements that occur on 15q11-q13 and provides useful information for prenatal diagnosis of PWS and AS.