When a man has a severely low sperm concentration (less than 10 million sperm per cubic centimeter of semen) or no sperm in the semen, there is a chance that he may have a genetic cause for it. There are a few known genetic causes of very low or even no sperm production. If there are too many chromosomes in the nucleus of a cell, or some parts of a chromosome switch place with other parts of another chromosome, or if some parts of a chromosome are missing, low sperm counts or even no sperm counts may result. The test for the number or arrangement of chromosomes is called a karyotype test. This is usually a blood test. In this test all the chromosomes in the nucleus of a cell are photographed and sorted out in pairs (one from each parent of the man). There should be 23 pairs including the pair that has an X chromosome from the man’s mother and a Y chromosome from the man’s father. If there are one too many X chromosomes in the pair this is known as Klinefelter’s syndrome. Klinefelter’s syndrome, also known as XXY karyotype, accounts for about 20% of cases of men with no sperm in the ejaculate.
There is an area on the Y chromosome itself that has the genetic code for sperm production. It has several regions that may be missing in whole or in part. These parts are commonly called “deleted in azoospermia (means no sperm) a, b, or c). 14% of men with severely low sperm counts will have this condition and 11% of men with no sperm in the semen will have this condition. If parts a or b are missing from the Y chromosome then typically there is no sperm production occurring and the patient may be advised to consider using a sperm donor. If part c is missing then there may be sperm in the semen and if not there still may be sperm in the testicle that could be obtained with a sperm retrieval surgery. The test which looks for missing genes along the Y chromosome (the male determining chromosome) is called a Y chromosome micro deletion test and it is performed on blood.
Other less common genetic causes include myotonic dystrophy, noonan syndrome, and androgen receptor gene mutations
Genetic causes of male infertility are currently not reversible so there are no current treatments which will cause a man with a genetic cause to produce normal amounts of sperm. Nonetheless, the technology currently exists to enable men with karyotype or Y chromosome abnormalities the possibility to father a child of their own even if there is no sperm in the semen. If sperm is present in the semen but at very low levels, in-vitro fertility ICSI can be performed. With this technology, only one sperm is needed for each egg that is obtained from the woman (typically 10 to 20 eggs). Only very few living sperm are needed after all. If no sperm is present in the semen, then a sperm retrieval surgery can be performed to look for and extract sperm that may be in the testicle. (See section on sperm retrieval surgeries) If a man has a genetic condition then it is possible that his child will be affected by it. If it is a Y chromosome micro deletion then his male children, who also must have a y chromosome which comes from him will have the same male infertility syndrome he has. If a man has XXY also known as Klinefelter’s syndrome, there is a possibility his son will have the condition, but not necessarily as a surprising majority of sons are born without the condition. If a man has a rearrangement of some of his other chromosomes, known as a “translocation” then there is a risk that more severe birth defects could occur in his child whether it is male or female. There are techniques to evaluate the embryos that are formed with in-vitro fertility before they are selected to be used which can be used to choose embryos without the genetic abnormality.