A female newborn having mosaicism with near-tetraploidy and trisomy 18.

Tetraploidy is characterized by the presence of four complete sets of chromosomes in an individual. Full tetraploidy is usually considered lethal. To date, only ten live-births with the condition have been reported. Trisomy 18 without neonatal intensive treatment is also known to be fatal. We report a female newborn who had mosaicism with near-tetraploidy and trisomy 18 (94, XXXX, +18, +18/47, XX, +18). She had features of conditions. The most plausible mechanism of the formation was a failure of cytoplasmic cleavage at the first division of the zygote. The longer survival of the patient compared with the 10 previously reported live-births with non-mosaic tetraploidy may be due to the dominance of the trisomy cells. We suggest that non-tetraploid cells, even when trisomic for chromosome 18, might contribute to longer survival in comparison to non-mosaic tetrapolid patients. (C) 2016 Wiley Periodicals, Inc.