We report a case of maternal uniparental disomy of chromosome 10 discovered after chorionic villus sampling (CVS). Direct preparations revealed mosaic trisomy 10, while cultured CVS cells, as well as amniotic fluid cells, showed only a normal 46,XY complement. DNA analysis using microsatellite markers showed both chromosomes 10 to have been inherited from the mother. The pregnancy was complicated by polyhydramnios. A phenotypically normal male infant of appropriate size was delivered by Caesarean section at 41 weeks' gestation. Since only the direct preparations showed trisomy 10, this case illustrates the importance of CVS direct preparations in the detection of pregnancies at risk of uniparental disomy (UPD). Although the increased frequency of confined placental mosaicism (CPM) diagnosed when direct preparations are performed has been viewed negatively, identification of both CPM and UPD may have biological and clinical significance for a pregnancy. Even though only a single case of maternal disomy 10 is reported here, the apparently normal phenotype provides evidence that there are no major imprinted loci on chromosome 10 that affect in utero growth and development. However, other potential effects such as mental retardation will require long-term follow-up of this as well as additional cases.

HH, et al. (1995)

We report a case of mosaicism for three cell lines: 45,X, 46,XX, and 47,XX,+12, diagnosed prenatally by amniocentesis done for advanced maternal age. Cord blood from the baby showed mosaicism for 45,X and 46,XX; cultures derived from multiple placental sites, villi, cord, membrane, and skin had varying proportions of all three cell lines. The patient at 18 months of age has mild physical dysmorphisms, hypotonia, delay in gross motor development, and age‐appropriate cognitive development. The literature reveals variable outcomes for individuals with either mosaic trisomy 12 or mosaic Turner syndrome. Parental origin of the chromosome involved in a proposed corrected trisomy and/or the percentage of cell types in affected organs might account for the variability in outcomes seen.

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