Detection of hidden Y mosaicism in Turner's syndrome: importance in the prevention of gonadoblastoma.

UNLABELLED: The presence of Y chromosome fragments in patients with Turner's syndrome (TS) is known to increase the risk of gonadoblastoma. The investigation of Y sequences is usually performed only in the presence of marker chromosomes and therefore does not rule out the presence of hidden mosaicism in patients with 45,X TS without any marker.

AIMS: 1. To investigate the presence of hidden Y mosaicism in non-mosaic 45,X patients with TS, using samples from different tissues, and its association with the development of gonadoblastoma.

STUDY DESIGN: Twenty patients with a 45,X karyotype were studied. The SRY and DYZ3 sequences were amplified by PCR, using genomic DNA from peripheral blood, oral epithelial cells and hair roots. Prophylactic gonadectomy was offered to the Y-positive patients.

RESULTS: The analysis of the different tissues revealed that seven (35%) out of the 20 patients studied presented hidden chromosome Y mosaicism. Four of these patients underwent prophylactic gonadectomy, and bilateral gonadoblastoma was found in one of them.

CONCLUSIONS: A systematic search for hidden Y chromosome mosaicism in patients with TS and 45,X karyotype is justified by the possibility of developing gonadoblastoma.