Prenatal diagnosis of a distal 3p deletion associated with fetoplacental chromosomal discrepancy and confined placental mosaicism detected by array comparative genomic hybridization.

OBJECTIVE: This study is aimed at prenatal diagnosis of a distal 3p deletion associated with fetoplacental chromosomal discrepancy and confined placental mosaicism, and providing evidence for the limitation of array comparative genomic hybridization (aCGH) on placental tissues for molecular cytogenetic characterization of prenatally detected aneuploidy. CASE REPORT: A 30-year-old woman underwent amniocentesis at 18 weeks of gestation because of maternal anxiety. Results of amniocentesis revealed a distal deletion of chromosome 3p. A malformed female fetus was delivered at 20 weeks of gestation with brachycephaly and facial dysmorphisms, and a cytogenetic analysis of the cord blood revealed a karyotype of 46,XX,del(3)(p26.1),inv(9)(p12q13). A whole-genome aCGH on uncultured cord blood and placental tissue was performed. The aCGH on cord blood revealed a 7.4-Mb deletion at 3p26.3-p26.1. However, the aCGH on placental tissue revealed a 32.42-Mb gene dosage increase at 3p26.1-p22.1 and a 26.28-Mb gene dosage increase at 1p36.33-p36.11 in addition to a 7.4-Mb deletion at 3p26.3-p26.1, indicating confined placental mosaicism for partial trisomy 3p (3p26.1→p22.1) and mosaicism for partial trisomy 1p (1p36.33→p36.11). The 7.4-Mb deleted region of 3p26.3-p26.1 contained the following genes: CHL1, CNTN4, CRBN, LRRN1, and ITPR1. CONCLUSION: Fetal tissue and amniocytes offer more reliable resources for aCGH characterization of prenatally detected aneuploidy compared with placental tissues. A molecular cytogenetic evaluation of prenatally detected aneuploidy using placental tissue should raise concerns of confined placental mosaicism and fetoplacental chromosomal discrepancy.

Prenatal diagnosis and molecular cytogenetic characterization of mosaic ring chromosome 13.

We present prenatal diagnosis and molecular cytogenetic characterization of de novo mosaic r(13). A 32-year-old woman underwent amniocentesis at 18 weeks of gestation because of maternal anxiety. Amniocentesis revealed a karyotype of 46,XY,r(13)[33]/45,XY,-13[19]. aCGH on uncultured amniocytes at repeated amniocentesis detected a 4.22-Mb deletion at 13q34. Interphase FISH on 100 uncultured amniocytes showed the ratio of r(13):-13:idic r(13) as 85%:13%:2%. The cord blood had a karyotype of 46,XY,r(13)[91]/46,XY,idic r(13)[6]/45,XY,-13[3]. The placenta had a karyotype of 46,XY,mar(13)[31]/45,XY,-13[3]. Metaphase FISH confirmed that the marker chromosomes in placenta were derived from chromosome 13. aCGH on cultured placental cells detected a 77.81-Mb deletion at 13q13.3-q34. The fetus postnatally manifested facial dysmorphism. Prenatal diagnosis of r(13) should alert mosaicism for deletion/duplication of r(13) and distal 13q deletion. Fetoplacental chromosomal discrepancy of r(13) may exist in case of mosaic r(13) detected by amniocentesis.

Discrepancy in cytogenetic results between amniotic fluid cells and other fetal tissues: A case report / 대한산부인과학회지

We present two fetuses who were prenatally diagnosed by amniocentesis as having chromosomal mosaicism but who had a normal karyotype in the fetal blood by cordocentesis. One of the both fetuses had Turner and the other had trisomy 20 mosaicism. The prognosis for Turner mosaicism and trisomy 20 mosaicism diagnosed prenatally has yet to be established. The pregnancy with 45,X/46,XX mosaicism was terminated at 23+3 weeks' gestation. Autopsy findings showed no features of Turner's syndrome. Postnatal cytogenetic analysis revealed 45,X[4]/46,XX[52] mosaicism in skin and 46,XX in the lung tissue. The other fetus had amniocytes with trisomy 20 mosaicism and fetal cord blood cells with a normal karyotype. The baby was delivered at 38+2 weeks' gestation. At birth and 3 months after birth, no apparent abnormal findings were found. These cases with chromosomal discrepancy among various fetal tissues are rare. Two cases were discussed with the review of literature.