Chromosomal mosaicism on amniotic interphase nuclei detected by multiprobe FISH.

So far classical prenatal detection of chromosome aberrations has been limit- ed to the evaluation of metaphase by means of time-consuming cytogenetic techniques. The MultiVision PGT test enables a simultaneous detection of aneuploidies of chromo- somes 13 ,18, 21, X, and Y, even 24 h after amniocentesis. In the presented case, this test detected prenatally a chromosomal mosaicism 69,XYY(35)/46,XY(65). This result was not confirmed after birth, by the same test on blood smear. The discrepancy is diffi- cult to explain. We present a case of a pregnant woman from a group of high-riskpregnancy. Ul- trasound examination, performed in the 17th week, revealed increased echogenicity of the foetal intestine, together with the presence of a "sandal gap" and shortening of the auricle. In the 24th week a two-week discrepancy between the foetal age evaluated by ultrasound and foetal age calculated from the last men- ses was observed. The biochemical results of CNS malformations markers were normal. However, in the MV PG-T test, 69,XYY triploidy was detected in 35% of cells, which could be evidence for 69,XYY/46,XY mosaicism (Figure 1). De- spite this the foetal karyotype analyzed 10 days later was that of a normal male and did not confirm the preliminary diagnosis. Additionally, the MultiVision PGT test was performed following a standard culture of amniocytes. The test revealed an increased percentage of interphase nuclei with a triploidy - 69,XYY - at the level of 42% in comparison to uncultured amniotic cells. The pregnancy was