Molecular and cytogenetic characterization of extra-structurally abnormal chromosomes (ESACs) found prenatally: outcome and follow-up

Identification, characterization and clinical implications of two markers detected at prenatal diagnosis

OBJECTIVES

Marker chromosomes are relatively rare in the general population as its identification at prenatal diagnosis. In this article, we identified and characterized two de novo supernumerary marker chromosomes in a mosaic form at prenatal diagnosis.

METHODS

The two cases presented were detected during prenatal diagnosis at 17 and 15 weeks of gestation. The analyses were performed due to the advanced maternal age. In both cases, parent's karyotypes were normal. The identification of the marker chromosomes was possible by FISH techniques.

RESULTS

One marker chromosome was derived from chromosome 5 and the other from chromosome 6. Both children are well at the moment.

CONCLUSION

The two cases described in the present paper, join to the ones already described in the literature. However these results are the first ones without any phenotypical anomalies, at least until the present. Every new characterization of marker chromosomes at prenatal diagnosis should be reported for determining a genotype-phenotype correlation, and thus be used for genetic counselling and risk evaluation.