Two cases of confined placental mosaicism for chromosome 4, including one with maternal uniparental disomy

Two cases of trisomy 4 mosaicism are reported including one with molecularl y confirmed uniparental disomy (UPD) of chromosome 4. Cytogenetic analysis of a chorionic villus sample (CVS) in Case 1 showed complete trisomy 4 in t rophoblast and diploidy in chorionic stroma. Amniotic fluid analysis demons trated a 46,XX complement. After intrauterine fetal death at 30 weeks, mole cular analysis confirmed the presence of trisomy 4 of maternal meiotic orig in, while fetal tissues showed maternal UPD for chromosome 4. Cultured CVS in Case 2 revealed trisomy 4 in 2/30 cells analyzed. This pregnancy resulte d in a healthy livebirth with biparental inheritance of chromosome 4. Molec ularly confirmed UPD4 has not been previously reported, and therefore, alth ough the adverse outcome in Case 1 is likely due to the trisomy 4 in the pl acenta, an imprinting effect associated with UPD4 cannot be excluded. Copyr ight (C) 2001 John Wiley & Sons, Ltd.