Chromosomal abnormalities in patients with sperm disorders

Chromosomal abnormalities are among the most common genetic causes of spermatogenic disruptions. Carriers of chromosomal abnormalities are at increased risk of infertility, miscarriage or birth of a child with unbalanced karyotype due to the production of unbalanced gametes. The natural selection against chromosomally abnormal sperm usually prevents fertilization with sperm barring in cases of serious chromosomal abnormalities. However, assisted reproductive technologies in general and intracytoplasmic sperm injection in particular, enable the transmission of chromosomal abnormalities to the progeny. Therefore, cytogenetic studies are important in patients with male factor infertility before assisted reproduction treatment. The purpose of the current study was to investigate the types and frequencies of chromosomal abnormalities in 724 patients with infertility and to estimate the risk of chromosomal abnormalities detection in subgroups of patients depending on the severity of spermatogenic disruption, aiming at identifying groups of patients in need of cytogenetic studies. Karyotype analysis was performed in 724 blood samples of men attending infertility clinic. Chromosomal preparation was performed by standard techniques. At least 20 GTG-banded metaphase plates with the resolution from 450 to 750 bands per haploid set were analysed in each case. When chromosomal mosaicism was suspected, this number was increased to 50. Abnormal karyotypes were observed in 48 (6.6%) patients, including 67% of autosomal abnormalities and 33% of gonosomal abnormalities. Autosomal abnormalities were represented by structural rearrangements. Reciprocal translocations were the most common type of structural chromosomal abnormalities in the studied group, detected with the frequency of 2.6% ( n = 19), followed by Robertsonian translocation, observed with the frequency of 1.2% ( n = 9). The frequency of inversions was 0.6% ( n = 4). Gonosomal abnormalities included 14 cases of sex chromosome aneuploidy and 2 cases of terminal deletion of Y chromosome. Klinefelter syndrome was detected in 67% of patients with azoospermia. A significant increase in the frequency of numerical chromosomal abnormalities was observed in a group of patients with azoospermia ( P < 0.001). No differences were detected in the frequency of structural abnormalities in subgroups of patients. An increase in the frequency of chromosomal abnormalities with the decrease of sperm count was observed. Chromosomal abnormalities were detected with frequency 1.1% in a group of patients with normospermia, 1.9% in a group of patients with asthenozoospermia, 4.3% in patients with asthenoteratozoospermia, 6.5% in patients with oligoasthenozoospermia, 11.6% in patients with oligoasthenoteratozoospermia and 35% in a group of patients with azoospermia. Significant increase of the prevalence of chromosomal abnormalities was detected in subgroups of patients with azoospermia ( P < 0.001) and oligozoospermia ( P = 0.001) as compared to patients with normozoospermia. These results are considered to be criteria for selection of patients in need of cytogenetic studies before in vitro fertilization cycles because of the highest risk of chromosomal abnormalities detection.