ABSTRACT

Klinefelter syndrome was the first human sex chromosomal abnormality to be reported, and close to 15% are mosaic cases, usually with two cell lines (47,XXY and 46,XY) and rarely with further cell lines. In this report, an infertile patient with low level 47,XXY and 46,XY mosaicism (4% by GTG banding) is presented. This mosaicism was confirmed by fluorescence in situ hybridization in lymphocyte nuclei and in sperm nuclei, 4.2% and 6.9%, respectively. In conclusion, for accurate genetic counseling concerning probands’ fertility and estimated karyotypes of their offspring, fluorescence in situ hybridization is recommended in addition to conventional techniques in mosaic Klinefelter syndrome patients.