Taiwanese Journal of Obstetrics & Gynecology (Apr 2016)

Prenatal diagnosis and molecular cytogenetic characterization of low-level true mosaicism for trisomy 21 using uncultured amniocytes

  • Chih-Ping Chen,
  • Yeou-Lih Wang,
  • Schu-Rern Chern,
  • Peih-Shan Wu,
  • Yen-Ni Chen,
  • Shin-Wen Chen,
  • Li-Feng Chen,
  • Meng-Shan Lee,
  • Chien-Wen Yang,
  • Wayseen Wang

DOI
https://doi.org/10.1016/j.tjog.2016.02.014
Journal volume & issue
Vol. 55, no. 2
pp. 285 – 287

Abstract

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Objective: We present a prenatal diagnosis and molecular cytogenetic characterization of low-level true mosaicism for trisomy 21 using uncultured amniocytes. Case report: A 35-year-old woman presented with a borderline-positive result of noninvasive prenatal testing for trisomy 21. She underwent amniocentesis at 18 weeks of gestation, which revealed a karyotype of 47,XY,+21(5)/46,XY(53). Repeat amniocentesis at 22 weeks of gestation revealed a karyotype of 47,XY,+21(6)/46,XY(26). Array comparative genomic hybridization (aCGH) analysis on uncultured amniocytes revealed mosaic levels of 10% to 15% for trisomy 21. Interphase fluorescence in situ hybridization (FISH) analysis on uncultured amniocytes revealed a mosaic level of 21.7% (28/129 cells) for trisomy 21. Following genetic counseling and detailed ultrasound examination, the parents decided to continue the pregnancy. The pregnancy was carried to term, and a normal 3664-g male baby was delivered. The cord blood lymphocytes had a karyotype of 47,XY,+21(2)/46,XY(38). Postnatal interphase FISH analysis of urine detected no trisomy 21 in all 39/39 urinary cells. The neonate was phenotypically normal at age 7 months. Conclusion: Low-level true mosaicism for trisomy 21 can be associated with a favorable fetal outcome. aCGH and interphase FISH analyses on uncultured amniocytes are useful for rapid confirmation of low-level true mosaicism for trisomy 21 at repeated amniocentesis.

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