Prenatal diagnosis of an extra der(4) resulting from a complex maternal chromosome translocation

Molecular cytogenetic investigation of a balanced complex chromosomal rearrangement carrier ascertained through a neonate with partial trisomies of 13 and 22

Complex chromosomal rearrangement (CCR) is a structural abnormality of chromosomes that rarely appears in individuals with normal phenotypes. A CCR involving chromosomes 9, 13, and 22 was ascertained in a phenotypically normal woman through a neonate with multiple congenital malformations and partial trisomies of 13 and 22. We diagnosed the CCR using high-resolution chromosome analysis and three-color fluorescence in situ hybridization (three-color FISH) analysis, and ascertained a balanced CCR without cryptic imbalances using array comparative genomic hybridization (array CGH) and FISH. In the present work, we report on the case together with a literature review.

Prenatal diagnosis of ade novo complex chromosome rearrangement (CCR) mediated by six breakpoints, and a review of 20 prenatally ascertained CCRs

OBJECTIVES

To describe the cytogenetic and FISH characterization of a prenatally diagnosed de novo complex chromosome rearrangement (CCR), showing the involvement of four chromosomes and six breakpoints, and review the literature concerning prenatally detected CCRs in order to obtain insights into addressing karyotype-phenotype correlations in prenatal genetic counseling.

METHODS

Conventional protocols were used to set up cultures and chromosome preparations. Commercial and homemade probes were used for the FISH analyses.

RESULTS

An apparently balanced de novo t(4;10;20) was prenatally identified by means of cytogenetic analysis. FISH revealed a rearrangement mediated by six breakpoints and the insertion of chromosome 8 material within the 4q region. The pregnancy was interrupted. The fetus showed malformations and anomalous cortical neuron migration. The assembled list of 20 prenatally detected CCRs points to the preferential involvement of chromosomes 4, 6 and 14. The involvement of chromosome 20 is described here for the first time.

CONCLUSIONS

FISH analysis is essential for the accurate definition of a complex rearrangement. Phenotype description of fetuses carrying CCRs investigated by means of molecular cytogenetic techniques may contribute to improving and personalizing genetic counseling in prenatal diagnosis.