title: Mosaic trisomy 2 at amniocentesis: prenatal diagnosis and molecular genetic analysis.
abstract: OBJECTIVE
  This study aims at presenting prenatal diagnosis of mosaic trisomy 2 and reviewing the literature.
  
  
  RESULTS
  A 32-year-old woman underwent amniocentesis at 21 weeks of gestation because of abnormal maternal serum biochemistry. Amniocentesis revealed a karyotype of 47,XY,+2[1]/46,XY[21] in in situ cultures. The single colony with trisomy 2 had two metaphase cells, and both had the karyotype of 47,XY,+2. Repeated amniocentesis was performed at 23 weeks of gestation. Interphase fluorescence in situ hybridization (FISH) analysis on uncultured amniocytes using a 2q11.1-specific probe RP11-468G5 (spectrum green) showed three green signals in 11 of 47 uncultured amniocytes, indicating 23.4% mosaicism for trisomy 2. The cultured amniocytes had a karyotype of 46,XY[20 colonies]. Polymorphic DNA marker analysis excluded uniparental disomy 2. The woman underwent the third amniocentesis at 25 weeks of gestation. Interphase FISH analysis on uncultured amniocytes revealed 9.4% (5/53 cells) mosaicism for trisomy 2. The cultured amniocytes had a karyotype of 46,XY[30 colonies]. Prenatal ultrasound was normal. The parents decided to continue the pregnancy to term, and a 3316-g baby was delivered with no phenotypic abnormalities. Cord blood had a karyotype of 46,XY[40 cells]. Interphase FISH analysis on uncultured urinary cells revealed 8.2% (4/49 cells) mosaicism for trisomy 2. The neonate was normal in growth and psychomotor development at 6 months of age.
  
  
  CONCLUSIONS
  Prenatal diagnosis of a single colony with two or more cells with trisomy 2 at amniocentesis should alert a clinically significant aneuploidy, and interphase FISH on uncultured amniocytes is useful for rapid confirmation of low-level trisomy 2 mosaicism at amniocentesis. The abnormal cell line of trisomy 2 may disappear after long-term amniocyte cultures.
authors.affiliation: Department of Medicine, Mackay Medical College, New Taipei City, Taiwan. cpc_mmh@yahoo.com
authors.forename: Chih-Ping
authors.initials: CP
authors.lastname: Chen
authors.forename: Yi-Ning
authors.initials: YN
authors.lastname: Su
authors.forename: Schu-Rern
authors.initials: SR
authors.lastname: Chern
authors.forename: Yu-Ting
authors.initials: YT
authors.lastname: Chen
authors.forename: Peih-Shan
authors.initials: PS
authors.lastname: Wu
authors.forename: Jun-Wei
authors.initials: JW
authors.lastname: Su
authors.forename: Chen-Wen
authors.initials: CW
authors.lastname: Pan
authors.forename: Wayseen
authors.initials: W
authors.lastname: Wang
mesh_terms: D059786:Abnormal Karyotype; D000328:Adult; D000649:Amniocentesis; D002889:Chromosomes, Human, Pair 2; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D050498:Live Birth / Q000235:genetics*; D008297:Male; D009030:Mosaicism; D011247:Pregnancy; D047929:Term Birth; D014314:Trisomy / Q000175:diagnosis*; D016216:Ultrasonography, Prenatal