IDENTIFICATION OF A CASE OF MATERNAL UNIPARENTAL DISOMY OF CHROMOSOME-10 ASSOCIATED WITH CONFINED PLACENTAL MOSAICISM

We report a case of maternal uniparental disomy of chromosome 10 disco vered after chorionic villus sampling (CVS). Direct preparations revea led mosaic trisomy 10, while cultured CVS cells, as well as amniotic f luid cells, showed only a normal 46,XY complement. DNA analysis using microsatellite markers showed both chromosomes 10 to have been inherit ed from the mother. The pregnancy was complicated by polyhydramnios. A phenotypically normal male infant of appropriate size was delivered b y Caesarean section at 41 weeks' gestation. Since only the direct prep arations showed trisomy 10, this case illustrates the importance of CV S direct preparations in the detection of pregnancies at risk of unipa rental disomy (UPD). Although the increased frequency of confined plac ental mosaicism (CPM) diagnosed when direct preparations are performed has been viewed negatively, identification of both CPM and UPD may ha ve biological and clinical significance for a pregnancy. Even though o nly a single case of maternal disomy 10 is reported here, the apparent ly normal phenotype provides evidence that there are no major imprinte d loci on chromosome 10 that affect in utero growth and development. H owever, other potential effects such as mental retardation will requir e long-term follow-up of this as well as additional cases.