Y chromosome infertility
Male infertility with oligozoospermia (a subnormal number of sperm) or azoospermia (the absence of sperm) caused by deletion or rearrangement of the long arm of the Y chromosome, as demonstrated by chromosome analysis or by molecular studies which may show microdeletions (of region AZFa, AZFb, or AZFc) of the Y chromosome.
Y chromosome infertility is considered as a diagnostic possibility when an otherwise healthy male proves to be infertile