Double trisomy (48,XXY,+21) in monozygotic twins: case report and review of the literature.

The occurrence of double aneuploidy in the same individual is a relatively rare phenomenon. We describe twin newborns with typical clinical features of Down's syndrome, of which one revealed 48,XXY,+21 GTG-band karyotype. The second newborn died 2 days after its birth, and was clinically diagnosed having Down syndrome. Due to the same clinical features of the twins, the common placenta and amniotic sac, we speculate that they were monozygotics and as a result the second newborn should also be a Klinefelter. The purpose of this report is to present a rare case of possible coincidence of double aneuploidy in newborn twins. A review of the literature showed that double trisomy (48,XXY,+21) in a twin newborn infant has never occurred.