Maternal uniparental disomy (UPD) for chromosome 14 (upd(14)mat) has been associated with a distinct phenotype. We describe the first case of maternal uniparental isodisomy for chromosome 14 detected prenatally, in a pregnancy with mosaicism for trisomy 14 observed in both a chorionic villus sample (CVS) and in amniocytes. Detailed analysis of polymorphic microsatellites showed that the fetus was essentially isodisomic for one of the mother's chromosomes 14 and that recombination had introduced a mid-long arm region of heterodisomy. The fetus, which died in utero at 18 weeks, showed no apparent pathological features. The case demonstrates for the first time a maternal meiosis II non-disjunction of chromosome 14 leading to a trisomic conception which has been incompletely corrected by 'rescue' in the early embryo.
Copyright 1999 John Wiley & Sons, Ltd.