Rapid positive confirmation of mosaicism for a small supernumerary marker chromosome as r(8) by interphase fluorescence in situ hybridization, quantitative fluorescent polymerase chain reaction, and array comparative genomic hybridization on uncultured amniocytes in a pregnancy with fetal pyelectasis

摘要

ObjectiveThis study aimed at presenting prenatal diagnosis and molecular cytogenetic characterization of a small supernumerary marker chromosome (sSMC) derived from chromosome 8 by fluorescencein situhybridization (FISH), quantitative fluorescent polymerase chain reaction (QF-PCR), and array comparative genomic hybridization (aCGH) on uncultured amniocytes.Materials, Methods, and ResultsA 32-year-old woman underwent amniocentesis at 19 weeks of gestation because of fetal pyelectasis. Amniocentesis revealed ade novoring-shaped sSMC in two of 21 colonies of cultured amniocytes. Repeated amniocentesis at 22 weeks of gestation revealed a karyotype of 47,XY,+mar[8]/46,XY[32] in cultured amniocytes. Spectral karyotyping and FISH confirmed that the sSMC was derived from chromosome 8. She underwent a third amniocentesis at 26 weeks of gestation. Oligonucleotide-based aCGH analysis on uncultured amniocytes demonstrated a 43 Mb genomic gain in chromosome 8 encompassing 8p22→q12.1. Polymorphic DNA marker analysis of the uncultured amniocytes revealed a maternal origin of the sSMC and excluded uniparental disomy 8. Interphase FISH analysis showed three D8Z2 signals in 8/40 (20%) of uncultured amniocytes. The cultured amniocytes had a karyotype of 47,XY,+r(8)(p22q12.1)[3]/46,XY[37]. The pregnancy was carried to term, and an apparently normal baby, weighing 3300?g, was delivered with mild hydronephrosis but no other phenotypic abnormalities. The cord blood was found to have a karyotype of 47,XY,+r(8)(p22q12.1)[2]/46,XY[38].ConclusionPrenatal diagnosis of fetal pyelectasis should alert obstetricians of chromosome aberration. Interphase FISH, QF-PCR, and aCGH analyses on uncultured amniocytes are helpful in rapid positive confirmation of an sSMC detected at amniocentesis.