Y-Chromosome Microdeletion

Microdeletions on the long arm of the Y chromosome (Yq) disrupt genes in the AZF (azoospermia factor) regions — AZFa, AZFb, and AZFc — that are essential for sperm development. They are found in approximately 10–15% of men with severe oligospermia or azoospermia.

AZFc deletions are most common and leave some sperm production intact; TESE can often retrieve sperm for ICSI. AZFa and AZFb deletions are more severe and usually result in complete absence of sperm with very low TESE success rates.

Sons born from ICSI using sperm from a man with a Y-microdeletion will inherit the deletion and face the same fertility challenges, so genetic counseling is recommended.