Twins with nonconcordant sexual aneuploidy.

Abstract
A pair of dizygotic twins with different abnormal karyotypes are presented. The chromosome anomaly is a sexual aneuploidy in both cases: 48,XXXXY in 1, 47,XXY in the 2nd. The origin of the chromosomal anomaly and the hypothetical relation between sexual aneuploidy and twinning is discussed. Further studies in twins are necessary to prove the not yet solved problems of non-disjunction and double ovulation.