Table 4.

Genetics and male infertility

Clinical diagnosis	Genetic tests	Most common defects	Incidence (%)
Congenital bilateral absence of vas deferens (CBAVD)	Cystic fibrosis (CFTR gene)	ΔF508, R117H	66
Non-obstructive azoospermia	Karyotype	47, XXY	15-30
		AZFa, AZFb*, AZFc	10-15
Severe (<5M/ml) oligozoospermia	Karyotype	47, XXY	1-2
		Translocation	0.2-0.4
	Y chromosome microdeletions	Partial AZFb, AZFc	7-10

CFTR = cystic fibrosis transmembrane conductance regulator;

AZF = azoospermia factor; ^*AZFb the most severe (DAZ gene—deleted in azoospermia) causes the most severe defects of spermatogenesis; AZFc causes the mildest defects of spermatogenesis