title: Common trisomy mosaicism diagnosed in amniocytes involving chromosomes 13, 18, 20 and 21: karyotype-phenotype correlations.
abstract: Karyotype-phenotype correlations of common trisomy mosaicism prenatally diagnosed via amniocentesis was reviewed in 305 new cases from a collaboration of North American cytogenetic laboratories. Abnormal outcome was noted in 10/25 (40%) cases of 47,+13/46, 17/31 (54%) cases of 47,+18/46, 10/152 (6.5%) cases of 47,+20/46, and in 49/97 (50%) cases of 47,+21/46 mosaicism. Risk of abnormal outcome in pregnancies with less than 50% trisomic cells and greater than 50% trisomic cells were: 26% (4/15) versus 60% (6/10) for 47,+13/46, 52% (11/21) versus 75% (6/8) for 47,+18/46, 4.5% (6/132) versus 20% (4/20) 47,+20/46, and 45% (27/60) versus 59% (22/37) for 47,+21/46. Phenotypically normal liveborns were observed with mean trisomic cell lines of 9.3% for 47,+13/46, 8.6% for 47,+18/46, 27% for 47, +20/46, and 17% for 47,+21/46. Cytogenetic confirmation rates were 46% (6/13 cases) for 47,+13/46 mosaicism, 66% (8/12 cases) for 47, +18/46, 10% (10/97 cases) for 47,+20/46, and 44% (24/54 cases) for 47,+21/46. There were higher confirmation rates in pregnancies with abnormal versus normal outcome: 50% versus 44% for 47,+13/46 mosaicism, 100% versus 33% for 47,+18/46, 66% versus 7% for 47, +20/46, and 55% versus 40% for 47,+21/46. Repeat amniocentesis is not helpful in predicting clinical outcome. It may be considered when there is insufficient number of cells or cultures to establish a diagnosis. Fetal blood sampling may have a role in mosaic trisomy 13, 18, and 21 as the risk for abnormal outcome increases with positive confirmation: 1/5 (20%) normal cases versus 5/8 (62%) abnormal cases. High resolution ultrasound examination(s) is recommended for clinical correlation and to facilitate genetic counselling.
authors.affiliation: New York University School of Medicine, New York, NY 10016, USA.
authors.forename: R
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authors.lastname: Wallerstein
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authors.lastname: Crandall
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authors.lastname: Harrison
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authors.lastname: Meisner
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authors.lastname: Mengden
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authors.lastname: Patil
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authors.initials: LJ
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mesh_terms: D000015:Abnormalities, Multiple / Q000235:genetics; D000649:Amniocentesis; D000653:Amniotic Fluid / Q000166:cytology; D002882:Chromosomes, Human, Pair 13; D002887:Chromosomes, Human, Pair 18; D002890:Chromosomes, Human, Pair 20; D004314:Down Syndrome / Q000235:genetics*; D005260:Female; D005313:Fetal Death / Q000235:genetics; D005317:Fetal Growth Retardation / Q000235:genetics; D006330:Heart Defects, Congenital / Q000235:genetics; D006801:Humans; D007621:Karyotyping; D009030:Mosaicism; D010641:Phenotype; D011247:Pregnancy; D011256:Pregnancy Outcome; D014314:Trisomy