Discrepancy between the fetus and extra-embryonic tissues in prenatally detected mosaic distal 5p deletion.

Discrepancy between the fetus and extra-embryonic tissues in prenatally detected mosaic distal 5p deletion: We present clinical and cytogenetic data on a second-trimester fetus with mosaic del(5)(p15.1) and the extra-embryonic tissues with a normal karyotype. A 34-year-old woman, gravida 2, para 0, underwent genetic amniocentesis at 20 weeks' gestation because of advanced maternal age. Cytogenetic analysis of the cultured amniocytes revealed mosaicism for a distal 5p deletion, mos 46,XY,del(5)(p15.1)[4]/46,XY[26]. The pregnancy was terminated subsequently. Postnatally, the fetus displayed a triangular face, hypertelorism, epicanthal folds, low-set ears, and micrognathia. A karyotype of mos 46,XY,del(5)(pl 5.1)/46,XY was found in the liver, lungs, skin, and cord blood, whereas, the placenta, amnion, and umbilical cord had a karyotype of 46,XY. Our observation of fetoplacental, fetoamniotic, and fetoumbilical discrepancies shows a limitation of using placenta, amnion, and umbilical cord as confirmatory tools for prenatally detected mosaic distal 5p deletion. Our case also reinforces the notion that amniocentesis offers a more reliable diagnosis, compared to chorionic villus sampling.