The unprecedented recurrent diploid/tetraploid mosaicism of trisomy-18 (mixoploidy; 4n+18/2n+18): clinical report.

We report on a 32-year-old woman who presented at gestational age of 14 weeks. During ultrasonographic examination, we discovered that her fetus had several important abnormalities, including a cystic hygroma, craniofacial defects (low-set ears, broad nose), heart defects (single atrium, single ventricle), agenesis of corpus callosum, limb defects (clenched hands, pes equinovarus). Chorionic villus sampling and karyotyping revealed diploid/tetraploid mosaicism with trisomy 18 (mixoploidy; 4n+18/2n+18). Her second pregnancy was terminated because of the same clinical manifestations 1 year prior. Her first pregnancy resulted in the birth of an entirely healthy boy. As far as know, no other similar case has been presented in the literature.