Mondo Description Male infertility with azoospermia or oligospermia due to single gene mutation is a rare, genetic male infertility due to sperm disorder characterized by the absence of a measurable amount of spermatozoa in the ejaculate (azoospermia), or a number of sperm in the ejaculate inferior to 15 million/mL (oligozoospermia), resulting from a mutation in a single gene known to cause azoo- or oligo-spermia. Sperm morphology may be normal.