Molecular cytogenetic characterisation of an interstitial deletion 12p detected by prenatal diagnosis

Abstract

Objectives: Deletions in the short arm of chromosome 12 are rare structural aberrations. Till now only ten patients with interstitial deletions are described in the literature. Here, we report on the first case detected by prenatal diagnosis. Chorionic villi sampling was performed in the 14th week of gestation, indicated by fetal abnormalities detected by ultrasound examination. Conventional cytogenetic and molecular cytogenetic techniques were applied to determine the correct karyotype of the affected fetus.

Results: Analysing Giemsa- and QFQ-stained chromosomes of the CVS short-term culture, a structural aberrant chromosome 12 was detected. Fluorescence in situ hybridisation with YAC-probes and CGH analysis with DNA extracted from native chorionic villi proved an interstitial deletion in the aberrant chromosome 12. The GTG-banded chromosomes of the CVS long-term culture confirmed these results. Analyses of the parental chromosomal sets yielded normal results, indicating a de novo aberration. Array CGH analysis was performed to determine accurately the deletion breakpoints. Finally, according to ISCN 2005, the karyotype could be determined as 46,XX.arr cgh 12p13.2p11.21(RP11-77I22-->RP11-144O23)x 1.

Conclusion: The presented case shows the power of modern cytogenetic methods, allowing a more detailed diagnosis in affected individuals, and therefore, facilitating a more reliable prenatal diagnosis.