[Chromosome abnormalities in male infertility].

On the basis of systematic cytogenetic studies carried out with men undergoing examination for infertility in the couple, it is now estimated that the incidence of chromosome anomalies is about 5 per cent. This rate is much higher than that observed in the general population (0.7 per cent). Anomalies in the sex chromosomes are the most frequently observed since they represent approximately 4 per cent of the cases, and the analysis of the various types of mutation shows a distinct predominance of the 47 chromosome composition, XXY, which is related to Klinefelter's syndrome. Autosome anomalies are also observed, notably Robertsonian and reciprocal translocations. They are more rare (about 1% of the cases), but the fact that they are linked with disturbances of spermatogenesis is an important element in understanding the control-mechanisms of this process. The occurrence in both man and animals of a non-random relationship between the forms of translocation and the X and Y chromosomes found in the seminal vesicle during the pachytene stage, suggests that this contact interferes with the normal process in which the X chromosome is inactivated. This interference could account for the observed deficits in spermatogenesis. The hypothesis is reinforced by the fact that female carriers of the same autosome translocations, whose two X chromosomes are normally active during the whole miotic prophase, have no fertility problems.