Congenital Bilateral Absence Of Vas Deferens

Congenital bilateral absence of the vas deferens (CBAVD) is a condition leading to male infertility.

Epidemiology

It accounts for 6% to 8% of cases of obstructive azoospermia and affects about 1/1,000 males. It is also found in 98% of males with cystic fibrosis.

Clinical description

Infertile patients with CBAVD produce small volumes of acidic sperm (<1 ml with a pH<7.0).

Etiology

In 1990, mutations in the CFTR gene (the causative gene for cystic fibrosis) were identified in 42% of patients in a population of infertile males with CBAVD, suggesting that CBAVD is a genital form of cystic fibrosis. Since then, an exhaustive analysis of the 27 exons of the CFTR gene has led to the classification of CBAVD patients into four groups: i) patients with two mutations in the CFTR gene (19%), ii) patients with one mutation in the CFTR gene and having the IVS8-5T allele in the trans position (33%), iii) patients with either a mutation in the CFTR gene or having the IVS8-5T allele (27%) and iv) patients with neither the IVS8-5T allele nor a mutation in the CFTR gene (21%).

Genetic counseling

The condition is transmitted as an autosomal dominant trait. The genetic data have important implications for genetic counselling: the method of intracytoplasmic microinjection of a single spermatozoon has successfully resolved the male infertility problem. However, the identification of a CFTR mutation in a CBAVD patient implies that a CFTR mutation in the patient's partner should be sought, as if a mutation is found, preimplantation or prenatal diagnosis can be proposed.