Klinische Bedeutung Y-chromosomaler Mikrodeletionen im Rahmen reproduktionsgenetischer Routinediagnostik bei schwerer männlicher Subfertilität

Prevalence of Y chromosome microdeletions in infertile men who consulted a tertiary care medical centre: the Münster experience

The long arm of the human Y chromosome is required for male fertility. Microdeletions in three different regions of the human Y chromosome, designated AZFa, AZFb and AZFc, respectively, are frequently associated with male infertility. The varying frequency of Y microdeletions found in cohorts of infertile men (0.4-55.5%) is probably related to the criteria by which the patients are selected. We report the diagnosis of Y chromosomal microdeletion in a total of 1,470 men who attended our infertility clinic, the largest sample of infertile patients to have been analysed to date. This cohort consists of three populations. The first subgroup comprises 228 selected patients with severely impaired spermatogenesis. Since microdeletions had also been reported in patients with less severe defects in spermatogenesis, we then intended to define the deletion frequency in unselected patients (population II: 378 patients). Population III comprises 864 prospectively selected patients and intracytoplasmic sperm injection candidates. Altogether, 19 patients with microdeletions were found (1.3%). The microdeletion frequencies in populations I, II and III were 3.5%, 0.3% and 1.2%, respectively. Our study helps to define a subgroup of infertile men at risk of Y chromosomal microdeletions, and strongly supports the recommendation that Y microdeletion analysis should be limited to azoospermic and severely oligozoospermic men and candidates for intracytoplasmic sperm injection.

Y chromosome microdeletion screening in infertile men

Molecular analysis of Y-chromosomal microdeletions is routinely performed in the work-up of male infertility, in order to establish a diagnosis and for genetic counseling of the couple, since such microdeletions are transmitted to the male offspring. The review of published data shows that microdeletions are relatively common in patients with azoospermia or severe oligozoospermia, with wide variations in the reported deletion frequency depending mainly on the selection criteria. In general, patients with proximal deletions, involving the AZFa and/or the AZFb region show severe defects of spermatogenesis with a high prevalence of Sertoli cell only syndrome, while deletions of the distal AZFb and of the AZFc region can be compatible with residual spermatogenesis. Microdeletions have been only sporadically found in normozoospermic patients. For the time being the molecular analysis of microdeletions of the Y chromosome is indicated in infertile patients with sperm concentration <5 x 10(6)/ml and in men undergoing assisted reproduction techniques, since the genetic defect and, most probably, the related infertility problem will be transmitted to the sons.