Prenatal diagnosis of mosaic trisomy 16 by amniocentesis in a pregnancy associated with abnormal first-trimester screening result (low PAPP-A and low PlGF), intrauterine growth restriction and a favorable outcome

Taiwan J Obstet Gynecol. 2021 Nov;60(6):1107-1111. doi: 10.1016/j.tjog.2021.09.026.

Abstract

Objective: We present prenatal diagnosis of mosaic trisomy 16 by amniocentesis in a pregnancy associated with an abnormal first-trimester screening result, intrauterine growth restriction (IUGR) and a favorable outcome.

Case report: A 27-year-old woman underwent amniocentesis at 18 weeks of gestation because of an abnormal first-trimester screening result with maternal serum free β-hCG of 1.474 multiples of the median (MoM), pregnancy associated plasma protein-A (PAPP-A) of 0.122 MoM and placental growth factor (PlGF) of 0.101 MoM, and a Down syndrome risk of 1/45. Amniocentesis revealed a karyotype of 47,XY,+16 [9]/46,XY [16] and an abnormal array comparative genomic hybridization (aCGH) result of arr (16) × 3 [0.54] compatible with 54% mosaicism for trisomy 16 in uncultured amniocytes. At 24 weeks of gestation, repeat amniocentesis revealed a karyotype of 47,XY,+16 [4]/46,XY [16] and an aCGH result of arr 16p13.3q24.3 (96,766-90,567,357) × 2.25 with a log2 ratio = 0.2 compatible with 20-30% mosaicism for trisomy 16 in uncultured amniocytes. Quantitative fluorescent polymerase chain reaction (QF-PCR) excluded uniparental disomy (UPD) 16. Interphase fluorescence in situ hybridization (FISH) analysis on uncultured amniocytes revealed 19.4% (12/62 cells) mosaic trisomy 16. Prenatal ultrasound revealed IUGR. At 36 weeks of gestation, a phenotypically normal baby was delivered with a body weight of 1900 g. The cord blood had a karyotype of 46,XY. QF-PCR analysis confirmed biparentally inherited disomy 16 in the cord blood and maternal-origin of trisomy 16 in the placenta. When follow-up at age two months, FISH analysis on 101 buccal mucosal cells and 32 urinary cells revealed no signal of trisomy 16.

Conclusion: Mosaic trisomy 16 at amniocentesis can be associated with IUGR and an abnormal first-trimester screening result with low PAPP-A and low PlGF. Mosaic trisomy 16 without UPD 16 at amniocentesis can have a favorable outcome, and the abnormal triosmy 16 cell line may disappear after birth.

Keywords: Intrauterine growth restriction; Mosaic trisomy 16; PAPP-A; PlGF; Prenatal diagnosis.

Publication types

  • Case Reports

MeSH terms

  • Adult
  • Amniocentesis / methods*
  • Chromosomes, Human, Pair 16
  • Comparative Genomic Hybridization
  • Female
  • Fetal Growth Retardation / diagnosis*
  • Fetal Growth Retardation / genetics
  • Humans
  • In Situ Hybridization, Fluorescence
  • Infant, Newborn
  • Mosaicism
  • Placenta Growth Factor / blood*
  • Pregnancy
  • Pregnancy Outcome
  • Pregnancy Trimester, First
  • Pregnancy-Associated Plasma Protein-A / analysis*
  • Prenatal Diagnosis / methods*
  • Trisomy / diagnosis*
  • Uniparental Disomy

Substances

  • Placenta Growth Factor
  • Pregnancy-Associated Plasma Protein-A

Supplementary concepts

  • Chromosome 16, trisomy