Prenatal diagnosis and molecular cytogenetics in a case of partial trisomy 14 and monosomy 21.

[monosomy 21]

We report an unbalanced translocation involving chromosomes 14 and 21 which presented as fetal ventriculomegaly at 33 weeks gestation . Second trimester ultrasound had indicated normal fetal anatomy , including normal intracranial structures . Parental karyotypes showed a paternal balanced translocation : 46 ,XY ,t (14 ;21 )(q 12 ;q 21 ). The unbalanced translocation in the fetus resulted in trisomy for 14 pter-->q 12 and monosomy for 21 pter-->q 21 . Postnatal examination showed that the male infant had a cleft palate , but no cleft lip , and mild dysmorphic features . Postnatal MRI revealed bilateral and symmetric dilatation of the occipital horns , atria , and temporal horns of the lateral ventricles . Molecular cytogenetic techniques were used to delineate further the breakpoint on chromosome 14 to a site distal of the D 14 S 1071 locus and the breakpoint on chromosome 21 to a region between D 21 S 1918 and D 21 S 1902 . More precise definitions of chromosomal breakpoints in such clinical cases should provide more accurate prognosis for individuals with unbalanced karyotypes and assist in the identification of putative developmentally important genes .