A newborn with ambiguous genitalia and a complex X;Y rearrangement

Background: In most mammals, sex is determined at the beginning of gestation by the constitution of the sex chromosomes, XY in males and XX in females. Case: Here we report an interesting case characterized by ambiguous genitalia and ovotestis in a newborn carrying an apparently female karyotype (46 XX). Array Comparative Genomic Hybridization (Array-CGH) revealed an unbalanced rearrangement resulting in the deletion of the distal Xp and the duplication of the proximal Xp contiguous region with presence of the Y chromosome from Ypter to Yq11. Fluorescent in situ hybridization (FISH) showed that this portion of the Y was translocated to the tip of the abnormal X and that the duplicated portion of chromosome X was inverted. Altogether, the abnormal chromosome was a dicentric one with the centromere of the Y chromosome apparently inactivated. Conclusion: The presence within the translocated Y chromosome of the SRY gene explains the devolopment of testes although it is not clear the reason for the genitalia ambiguity.