Center for Human Genetics and Laboratory Diagnostics, Dr. Klein, Dr. Rost and Colleagues

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Azoospermia [N46]

OMIM numbers: 415000

Dr. rer. nat. Karin Mayer, Dipl.-Biol. Christine Schack,
Dipl.-Biol. Christina Sofeso

Scientific Background

Approximately 0.6–1% of all infertile men have microdeletions in the azoospermia factor (AZF) region of the Y chromosome. In the case of non-obstructive azoospermia, the prevalence of AZF microdeletions is 15–20%, in the case of severe oligozoospermia approx. 7–10%. The genes DAZ and RBM, which are essential for spermatogenesis are located in the AZF region. Deletions in this region lead to testicular maturation arrest or have been associated with the formation of immature, condensed sperm.

Through amplification of a total of six Y chromosomal markers from the regions AZFa, AZFb and AZFc, approximately 90% of all known deletions can be detected. Deletions of the AFZa or AZFb region always result in azoospermia; therefore, testicular sperm extraction (TESE) does not seem to be an option for couples with a desire for children. AZFc deletions, however, lead to a very heterogenous clinical picture, ranging from severe oligozoospermia to azoospermia. In approximately 50% of all men with AZFc deletions, sperm can be found during testicular biopsy with TESE (testicular sperm extraction). Deletions in the AZFc region are transmitted to male offsprings after in-vitro fertilization by ICSI (intracytoplasmatic sperm injection).