title: Parental mosaic trisomy 21 detected following maternal cell contamination of an amniotic fluid specimen from a normal male pregnancy.
abstract: We report a case of maternal mosaic trisomy 21 ascertained at prenatal diagnosis as a result of maternal cell contamination of an amniotic fluid sample. A 34 year old female was referred for karyotyping because of a previous trisomy 21 pregnancy. Chromosome analysis of primary in situ cultures showed a karyotype of 47,XX, + 21[6]/46,XY[32]/46,XX[2]. Molecular testing demonstrated maternal cell contamination of the amniotic fluid sample and G-banded karyotyping of maternal blood showed that 3/200 cells had trisomy 21, consistent with the mother being a Down syndrome mosaic. A normal male baby with a 46,XY chromosome complement was delivered at 30 weeks. This case emphasises the need for close collaboration between cytogenetic and molecular genetics laboratories in resolving unusual cases of mosaicism.
authors.forename: Melissa L
authors.initials: ML
authors.lastname: Street
authors.forename: John C K
authors.initials: JC
authors.lastname: Barber
authors.forename: Tracy A
authors.initials: TA
authors.lastname: Boyle
authors.forename: Katrina H
authors.initials: KH
authors.lastname: Ellis
authors.forename: Hilary
authors.initials: H
authors.lastname: Bullman
authors.forename: Tessa
authors.initials: T
authors.lastname: Homfray
mesh_terms: D000328:Adult; D000649:Amniocentesis; D000653:Amniotic Fluid / Q000166:cytology; D016477:Artifacts; D002478:Cells, Cultured; D004314:Down Syndrome / Q000175:diagnosis* / Q000235:genetics; D005260:Female; D006801:Humans; D008297:Male; D009030:Mosaicism; D009035:Mothers; D011247:Pregnancy