Mosaic trisomy 7 at amniocentesis: prenatal diagnosis and molecular genetic analyses.
OBJECTIVE
To present prenatal diagnosis and molecular genetic analyses of mosaic trisomy 7.


RESULTS
A 38-year-old primigravid woman underwent amniocentesis at 19 weeks of gestation because of her advanced maternal age. Amniocentesis revealed a karyotype of 47,XY,+7[26]/46, XY[16]. Repeated amniocentesis at 21 weeks of gestation revealed a karyotype of 47,XY,+7[20]/46,XY[17]. Simultaneous cordocentesis revealed a karyotype of 46,XY in 100/100 cultured lymphocytes. Polymorphic DNA marker analyses of uncultured amniocytes and cord blood revealed a diallelic pattern with seemingly equal biparental inheritance of chromosome 7. Repeated cordocentesis and chorionic villus sampling at 23 weeks of gestation revealed a karyotype of 47,XY,+7[2]/46,XY[66] in cord blood and a karyotype of 47,XY,+7 in 24/24 cultured chorionic villi cells. Level II ultrasonography was normal. At 40 weeks of gestation, a 2,708 g normal male baby was delivered. The peripheral blood had a karyotype of 46,XY in 100/100 lymphocytes. Molecular analyses of placenta, urine, buccal swab, and peripheral blood revealed a diallelic pattern and seemingly equal biparental inheritance of chromosome 7 in all tissues. At 3 months of age, he manifested hypopigmented skin and inguinal hernia, but showed normal growth and mental development. Fluorescence in situ hybridization analysis of inguinal hernia sac tissue revealed that 19/100 (19%) of nuclei had three chromosome 7 signals.


CONCLUSIONS
Mosaic trisomy 7 at amniocentesis may be derived from a cell culture artifact from an undetected low level of trisomy 7 mosaicism in uncultured amniocytes, and can be associated with favorable fetal outcome if the blood has a normal karyotype or a very low level of mosaicism and if uniparental disomy for chromosome 7 is excluded.
Department of Obstetrics and Gynecology, Mackay Memorial Hospital, Taipei, Taiwan. cpc_mmh@yahoo.com
Chih-Ping
CP
Chen
Yi-Ning
YN
Su
Schu-Rern
SR
Chern
Yuh-Ming
YM
Hwu
Shuan-Pei
SP
Lin
Chyong-Hsin
CH
Hsu
Fuu-Jen
FJ
Tsai
Tao-Yeuan
TY
Wang
Pei-Chen
PC
Wu
Chen-Chi
CC
Lee
Yu-Ting
YT
Chen
Li-Feng
LF
Chen
Wayseen
W
Wang
D000328:Adult; D000649:Amniocentesis; D002869:Chromosome Aberrations; D002897:Chromosomes, Human, Pair 7 / Q000235:genetics; D005260:Female; D006552:Hernia, Inguinal / Q000175:diagnosis / Q000235:genetics*; D006801:Humans; D017496:Hypopigmentation / Q000175:diagnosis / Q000235:genetics*; D007223:Infant; D008297:Male; D009030:Mosaicism; D011247:Pregnancy; D011256:Pregnancy Outcome; D014314:Trisomy / Q000175:diagnosis / Q000235:genetics; D024182:Uniparental Disomy / Q000175:diagnosis / Q000235:genetics