Gonadal dysgenesis in a neonate with 45,X/47,XXX karyotype

A case of X/XXX mosaicism in a neonate with dysgenetic gonads is presented because of the rarity of the X/XXX karyotype and the presence of dysgenetic ovaries and congenital heart anomalies. We suggest that the X/XXX mosaicism may not have a protective effect on the gonads as does X/XX mosaicism in some cases.