Congenital Bilateral Aplasia Of The Vas Deferens (CBAVD) [Q55.4]
Dr. rer. biol. hum. S. Chahrokh-Zadeh, Dr. rer. nat. Annett Wagner
CBAVD results in male infertility and may occur isolated or as a manifestation of cystic fibrosis (CF, mucoviscidosis). The cause for the infertility is an obstruction of the transport channels in the male reproductive system due to degenerative changes. CBAVD is understood to be an atypical form of CF or CFTR-RD (related disease) and is caused by mutations in the CFTR gene. These mutations disrupt the function of chloride channels in the apical cell membrane of epithelial cells, leading to a change in the salt content in sweat and other body fluids.
The heterozygote frequency for CFTR mutations within the Caucasian population is estimated to be 1 in 25. However, other mutations are found in CBAVD than in CF; in 40-50% of all cases, three mutations can be detected in Caucasians: F508del, R117H and the 5T allele. A combination of a “severe” mutation (e.g. F508del) and a “mild” mutation (e.g. R117H) or two “mild” mutations are typical for CBAVD. If only one mutation can be detected, it still has to be assumed that a second one is present which cannot be detected with the current diagnostic methods. It is recommended to also test the partner of a CFTR mutation carrier for mutations in the CFTR gene before an in-vitro fertilization (ICSI). If a CFTR mutation is present in both partners, there is a risk for mucoviscidosis in mutual children. A genetic consultation is therefore recommended.