Genetic changes in the CF gene can cause a variety of complications, ranging from no symptoms at all to the classic symptoms of CF. In the middle falls a range of medical concerns including chronic respiratory infections, pancreatic insufficiency, and male infertility.

Genetic changes in the CF gene can cause infertility in men. They cause a condition called CBAVD, or congenital bilateral absence of the vas deferens. Almost all men with CF have CBAVD and therefore experience infertility.

These genetic variations in the CFTR gene can also cause CBAVD in men who do not have the classic symptoms of CF. Genetic testing offered through DNA Direct identifies the 32 most common mutations related to CF, including the mutations and variations that can cause CBAVD (with or without classic CF symptoms).

Women with CF may experience reduced fertility and pregnancy complications, mainly due to the severity of the disease. However, these genetic changes are not known to have a similar impact on fertility as seen in men. So, while genetic testing guidelines recommend that CF screening be offered as part of the evaluation for male infertility, screening is not currently recommended as part of a female infertility work-up.

What is CBAVD
What Causes CBAVD
What can I do if I have CF-related CBAVD?

What is CBAVD?

CBAVD (congenital bilateral absence of the vas deferens) refers to the improper development of the tube through which sperm are released from the testes. CBAVD is present at birth, but most men do not become aware of it until they have difficulty with fertility.

Having CBAVD is like being born with a vasectomy: you have sperm, but the pathway to release them is missing.

CBAVD occurs in almost all men with CF, but it can also occur in men who do not have a CF diagnosis. Some of these men have genetic changes in the CF gene associated with the condition, while others have other, non-CF causes.

Here are some facts about CBAVD:

• CBAVD accounts for 1 to 2 percent of male infertility
• 98 percent of men with CF are born with CBAVD
• 64 to 85 percent of men with CBAVD without a CF diagnosis are found to have at least one underlying genetic change or variation in the CF gene
• 19 percent of these men are found to have two genetic changes

It is important that men who have CBAVD and are found to have changes in the CF gene have a physical evaluation to make sure they do not also have any subtle lung or digestive problems that can occur in CF.

What causes CBAVD?

Genetic mutations and variations in the CF gene cause CBAVD. Anyone who is found to carry a mutation known as R117H should also have a second round of testing to look for a specific variation in the CF gene – known as the 5T allele.

The 5T allele is considered a genetic variation (rather than a mutation) because it is found in about 5 percent of the general population. By itself, it does not cause CF or male infertility. However, when combined with other CF mutations – especially the R117H mutation -- it is associated with CBAVD and can lead to features of CF depending on what other genetic changes are present.

Thus, any man who has experienced infertility or who has CBAVD should be screened for CF and tested for the 5T allele variation. Many of these men have no symptoms and no family history of CF.

DNA Direct offers an Infertility Panel that includes CF Testing and 5T allele screening for men.

What can I do if I have CF-related CBAVD?

Men with CBAVD have a number of options to help them conceive with their partners. Since they have functional sperm but have a block in the pathway that releases the sperm, family planning options that use their sperm rely on assisted reproductive technology (ART).

ICSI (intracytoplasmic sperm injection) is an option that is currently available. It is important to realize that these involve going to a fertility specialist or IVF (in vitro fertilization) clinic.

DNA Direct's Cystic Fibrosis Panel tests for the 32 most common CF mutations, which detect about 90 percent of CF mutations.

For men experiencing infertility or who have a diagnosis of congenital absence of the vas deferens (CBAVD), DNA Direct also tests for the 5T allele.