Investigation of genetic etiologies in patients with non-obstructive azoospermia

Introduction and Objective: Azoospermia is the absence of sperm in the ejaculate, including centrifuged semen pellet, and is a common cause of male infertility, accounting for 10-15% of cases. Non-obstructive azoospermia (NOA) is suspected in the presence of small testicular volume, normal semen volume and elevated FSH. Routine genetic evaluation of NOA includes chromosome analysis and Y chromosome microdeletion (YCM) analysis. Sequencing technologies developed in the last 20 years have contributed to revealing genetic causes in the field of male infertility. In this study, we aimed to investigate new genetic causes in NOA patients. Methods: Between November 2022 and June 2024, 31 adult men admitted to the medical genetics outpatient clinic of KTU Farabi Hospital for NOA were included in the study. Patients with secondary causes of azoospermia were not included in the study. All 31 patients first underwent chromosome analysis and YCM analysis. Whole Exome Sequencing (WES) test was performed in 25 patients in whom no cause was found to explain azoospermia. Results: The median age at presentation for genetic evaluation was 31 (22-46) years. There was a family history of infertility in 61% of cases and consanguinity between parents in 55%. Chromosomal disorders (47, XXY (3 cases), 45,X/46,X,del(Y)(q11.23) (1 case), 46,X,der(Y) t(Y;?)(q12;p13) (1 case)) were detected in 16.1% of the 31 NOA cases and YCM (AZFc deletion) was detected in 3.2% (1 case). In 16% of 25 NOA patients who underwent WES, a cause that could explain the clinic was found in MSH4 (2 cases), STAG3 (1 case) and NR5A1 (1 case) genes. Novel c.2639_2640del, p.Pro880ArgfsTer14 variation in MSH4 gene was found homozygous in two unrelated cases from two different families. Novel c.671C>G, p.Ser224Ter variation in STAG3 gene was homozygous and NR5A1 gene c.251G>T, p.Arg84Leu variation was heterozygous. Conclusion: The use of WES in NOA cases has become widespread in recent years. In this study, the success rate of genetic diagnosis in NOA cases with chromosomal analysis, YCM and WES was 32.2% (10/31). The use of WES in NOA cases increases the success of genetic diagnosis and helps infertile couples in the process of pregnancy planning.