AZFb

AZFb, short for azoospermia factor B, is a subregion of the Y chromosome’s AZF (Azoospermia Factor) region that is essential for normal spermatogenesis. It lies on the long arm of the Y chromosome (Yq11) and contains a cluster of genes, including the RBMY gene family, that participate in germ cell development and meiosis. Deletions spanning AZFb disrupt these genes and lead to impaired sperm production.

Clinically, AZFb deletions are a recognized cause of male infertility. They most often present with non-obstructive azoospermia or severe oligospermia. Histologically, sperm development is frequently arrested during meiosis, and many men have little or no mature sperm in the testes. Sperm retrieval by TESE is generally unsuccessful, although rare cases with limited residual spermatogenesis have been reported.

Diagnosis is established through Y chromosome microdeletion testing, typically using PCR-based assays that detect sequence-tagged sites spanning the AZF regions. An AZFb deletion is reported as part of a panel evaluating deletions in AZFa, AZFb, and AZFc.

Management and genetic counseling focus on fertility options and family planning. There is no proven cure to restore natural spermatogenesis for AZFb deletions. If sperm are retrieved and used for assisted reproduction, success rates are low. The AZFb deletion is inherited along the Y chromosome, so male offspring conceived with the father’s Y chromosome will also carry the deletion. Genetic counseling should address the implications for affected individuals and potential transmission to male descendants.