Estimates of sperm sex chromosome disomy and diploidy rates in a 47,XXY/46,XY mosaic Klinefelter patient

A 47,XXY/46,XY male was investigated for the incidence of aneuploidy in spe rm sex chromosomes using a three-colour X/Y/18 fluorescence in situ hybridi sation (FISH) protocol. A total of 1701 sperm nuclei were analysed. The rat io of X-bearing to Y-bearing sperm did not differ from the expected 1 : 1 r atio although there were more 23,Y sperm than 23,X sperm (844 vs 795). Ther e was a significantly increased proportion of disomy XY and XX sperm compar ed with normal controls (0.41% vs 0.10%, P < 0.001 and 0.29% vs 0.04%, P < 0.01). However, the incidence of YY sperm was similar to the controls (0.06 % vs 0.02%). The diploidy rate was also significantly increased (1.7% vs 0. 13%, P < 0.0001), as was disomy 18 (0.71% vs 0.09%) and 25,XXY (0.47% vs 0% ). The results support the hypothesis that some 47,XXY cells are able to un dergo meiosis and produce mature spermatozoa. Patients with mosaic Klinefel ter syndrome with severe oligozoospermia have significantly elevated incide nces of disomy XY and XX sperm and may be at a slightly increased risk of p roducing 47,XXX and 47,XXY offspring. Additionally, they may be at risk of producing offspring with autosomal trisomies. Hence, patients with Klinefel ter mosaicism scheduled for intracytoplasmic sperm injection intervention s hould first undergo FISH analysis of their sperm to determine their risk.