A) NUMERICAL CHROMOSOME ABNORMALITIES
1) Klinefelter Syndrome
This syndrome was first described by Harry Klinefelter in 1942 as a clinical condition with small testes, azoospermia, gynecomastia and an elevated serum FSH. (56) Only in 1959 was the chromosomal basis of the disorder described. Subsequently the diagnosis of Klinefelter syndrome has required the demonstration of the 47,XXY karyotype or one of its rarer variants. (57)
The prevalence of Klinefelter syndrome appears to be approximately 1 in 660 males, and recent data suggest a rising incidence over the last decades. (58) It is the most frequent form of primary testicular dysfunction affecting spermatogenesis as well as hormone production and is found in…show more content… The group difference between boys with Klinefelter syndrome and controls amounts to 11 points in full scale IQ (92 versus 103), and deficits are observed primarily in cognitive and verbal abilities. (64) Compared with their classmates certain abnormal physical and psychological characteristics of the patients become obvious and they may become socially alienated. Higher-grade aneuploidy of the sex-chromosomes (48,XXXY, 48,XXYY and 49,XXXXY) is associated with mild mental retardation. In comparison clinical symptoms is very few in Klinefelter patients with chromosome mosaics (47,XXY/46,XY).…show more content… (66) The rate of diploidy of sperm as well as disomy for gonosomes and autosomes seems to be increased in patients with Klinefelter syndrome, however, the majority of sperm appear to be normal. (67) Preliminary data suggest that in about 20 - 50 percent of patients with Klinefelter syndrome it may be possible to retrieve sperm by TESE. (68) Several pregnancies have been achieved with testicular sperm used for ICSI. The embryos show normal or aneuploid karyotypes which can be identified by preimplantation or prenatal diagnosis. Interestingly, the birth of normal children conceived by assisted reproductive techniques seems to be rule, suggesting that the few sperm which can be found in about 50% of patients with Klinefelter syndrome possibly derive from the clonal expansion of spermatogonia with unremarkable karyotype problems.