Genetic Causes of Male Infertility and Treatment
The man’s role in fertility is to produce healthy sperm that can be delivered to their ultimate destination, the egg. There are three kinds of genetic factors that can be a common cause of sperm abnormalities.
Male chromosome abnormalities
For men with extreme sperm abnormalities, up to 15 percent have some type of chromosome abnormality. This can be diagnosed by a karyotype – a test (usually on a blood sample) to identify and evaluate the size, shape, and number of chromosomes in body cells.
Men with chromosome abnormalities are also at greater risk of fathering children with chromosome abnormalities, too. In addition, these men are a higher risk of fathering sons with their own infertility problems.
Male chromosome abnormalities are reason for men and their female partners who become pregnant to consider prenatal diagnosis, either amniocentesis, in which fluid in the sac surrounding the fetus is tested for genetic problems, or chorionic villus sampling (CVS), in which tiny fingerlike growths in the placenta are sampled and tested.
Y chromosome microdeletions
As many as 20 percent of men with severe sperm abnormalities may have normal chromosomes but may be missing very tiny areas of the Y chromosome, called microdeletions. Genes located in these areas are very important for the production of healthy sperm.
Currently, many physicians and scientists believe that the main effect of microdeletion is passage to male children, rendering them infertile. Regardless, only detailed DNA analysis can identify microdeletions. This testing should be considered for all men suffering male-factor infertility but who have otherwise tested normal in a chromosome study.
Cystic fibrosis & CAVD
A very small number of males – about one to two percent – are infertile because they were born without the vas deferens, the coiled tube connecting the testes to the urethra and transporting sperm from the epididymis to the ejaculatory duct. This is often the problem in men with azoospermia, the lack of any measurable level of sperm in the semen.
Known as congenital absence of the vas deferens (CAVD), this condition is also associated with an increased chance to be a carrier for a gene that cystic fibrosis (CF). An incurable and fatal disease, CF affects the mucous glands of vital organs, leading to breathing problems, infections, lung damage, and digestive problems.
Both parents must be carriers of cystic fibrosis to be at risk for passing the disease to a child. More than four of five men with CAVD are carriers for at least one genetic mutation known to cause CF.
This makes it imperative for men with azoospermia and/or known CAVD and their female partners to undergo CF carrier testing. Moreover, sons of men with CAVD may also be at increased risk of having CAVD.
A diagnosis of severe male-factor infertility is reason for a couple to consider genetic counseling to evaluate their risk.
For most men with these kinds of conditions to become fathers, they will need intracytoplasmic sperm injection (ICSI), a laboratory process in which sperm is injected directly into an egg with a tiny needle as part of in vitro fertilization (IVF).
Some couples facing similar challenges might also consider pre-implantation genetic diagnosis (PGD), for detection of possible abnormalities in embryos created from the male’s sperm. Again, genetic counseling can help determine the risk.