Mosaic tetrasomy 9p at amniocentesis: prenatal diagnosis, molecular cytogenetic characterization, and literature review.
OBJECTIVE
This study was aimed at prenatal diagnosis of mosaic tetrasomy 9p and reviewing the literature.


METHODS
A 37-year-old woman underwent amniocentesis at 20 weeks' gestation because of advanced maternal age and fetal ascites. Cytogenetic analysis of cultured amniocytes revealed 21.4% (6/28 colonies) mosaicism for a supernumerary i(9p). Repeat amniocentesis was performed at 23 weeks' gestation. Array comparative genomic hybridization, interphase fluorescence in situ hybridization, and quantitative fluorescent polymerase chain reaction were applied to uncultured amniocytes, and conventional cytogenetic analysis was applied to cultured amniocytes.


RESULTS
Array comparative genomic hybridization analysis of uncultured amniocytes detected a genomic gain at 9p24.3-9q21.11. Interphase fluorescence in situ hybridization analysis of uncultured amniocytes using a 9p24.3-specific probe RP11-31F19 (spectrum red) showed four red signals in 47.1% (49/104 cells) in uncultured amniocytes. Cytogenetic analysis of cultured amniocytes revealed a karyotype of 47,XX, +idic(9)(pter→q21.11::q21.11→pter)[4]/46,XX[20] and 16.7% (4/24 colonies) mosaicism for tetrasomy 9p. Quantitative fluorescent polymerase chain reaction confirmed a maternal origin of tetrasomy 9p. The pregnancy was terminated, and a malformed fetus was delivered with hydrops fetalis and facial dysmorphism. The fetal blood cells had 32.5% (13/40 cells) mosaicism for tetrasomy 9p.


CONCLUSIONS
Mosaic tetrasomy 9p at amniocentesis can be associated with fetal ascites and hydrops fetalis. The mosaic level of tetrasomy 9p may decrease after long-term tissue culture in amniocytes in case of mosaic tetrasomy 9p.
Department of Obstetrics and Gynecology, Mackay Memorial Hospital, Taipei, Taiwan; Department of Medical Research, Mackay Memorial Hospital, Taipei, Taiwan; Department of Biotechnology, Asia University, Taichung, Taiwan; School of Chinese Medicine, College of Chinese Medicine, China Medical University, Taichung, Taiwan; Institute of Clinical and Community Health Nursing, National Yang-Ming University, Taipei, Taiwan; Department of Obstetrics and Gynecology, School of Medicine, National Yang-Ming University, Taipei, Taiwan. Electronic address: cpc_mmh@yahoo.com.
Chih-Ping
CP
Chen
Department of Obstetrics and Gynecology, Mackay Memorial Hospital, Taipei, Taiwan.
Liang-Kai
LK
Wang
Department of Medical Research, Mackay Memorial Hospital, Taipei, Taiwan.
Schu-Rern
SR
Chern
Gene Biodesign Co. Ltd, Taipei, Taiwan.
Peih-Shan
PS
Wu
Department of Medical Research, Mackay Memorial Hospital, Taipei, Taiwan.
Yu-Ting
YT
Chen
Department of Obstetrics and Gynecology, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan.
Yu-Ling
YL
Kuo
Department of Obstetrics and Gynecology, Mackay Memorial Hospital, Taipei, Taiwan.
Wen-Lin
WL
Chen
Department of Obstetrics and Gynecology, Mackay Memorial Hospital, Taipei, Taiwan.
Meng-Shan
MS
Lee
Department of Medical Research, Mackay Memorial Hospital, Taipei, Taiwan; Department of Bioengineering, Tatung University, Taipei, Taiwan.
Wayseen
W
Wang
D000328:Adult; D000649:Amniocentesis; D000650:Amnion / Q000166:cytology*; D000782:Aneuploidy; D002478:Cells, Cultured; D002899:Chromosomes, Human, Pair 9 / Q000235:genetics; D055028:Comparative Genomic Hybridization; D005260:Female; D006801:Humans; D009030:Mosaicism; D011247:Pregnancy
amniocentesis; mosaicism; supernumerary isochromosome 9p; tetrasomy 9p