Prenatal diagnosis and molecular cytogenetic characterization of a familial small supernumerary marker chromosome derived from the acrocentric chromosome 14/22

ObjectiveWe present prenatal diagnosis and molecular cytogenetic characterization of a familial small supernumerary marker chromosome (sSMC) derived from the acrocentric chromosome 14/22.Case reportA 40-year-old, gravida 2, para 1, woman underwent amniocentesis at 17 weeks of gestation because of advanced maternal age. Amniocentesis revealed a karyotype of 47,XY,+mar. Prenatal ultrasound was unremarkable. Simultaneous array comparative genomic hybridization (aCGH) analysis on the DNA extracted from uncultured amniocytes revealed no genomic imbalance. Cytogenetic analysis of the parental bloods revealed a karyotype of 47,XY,inv (9) (p12q13),+mar in the father and a karyotype of 46, XX in the mother. The sSMC was investigated by fluorescence in situ hybridization (FISH) analysis on cultured amniocytes using the CEP 13/21 α-satellite specific gene probe labeled with fluorescein isothiocyanate (FITC) fluorophore and the CEP 14/21 α-satellite specific gene probe labeled with Texas Red fluorophore (Cytocell Inc.). The result showed that the sSMC was derived from the chromosome 14/22, or+mar.ish dic (14/22) (D13Z1/D21Z1-, D14Z1/D22Z1+)[20]. A healthy male baby was delivered at term with no phenotypic abnormality. Quantitative fluorescent polymerase chain reaction (QF-PCR) analysis on parental bloods and the child's peripheral blood was used to exclude uniparental disomy (UPD) (14) and UPD(22).ConclusionFISH analysis is useful for the determination of an sSMC derived from an acrocentric chromosome under the circumstance of no genomic imbalance at amniocentesis. QF-PCR analysis is useful for excluding the possible associated UPD.