Congenital unilateral absence of the vas deferens: a heterogeneous disorder with two distinct subpopulations based upon aetiology and mutational status of the cystic fibrosis gene.

A total of 21 infertile men with congenital unilateral absence of the vas deferens (CUAVD) were studied to determine if this disorder involves mutations in the cystic fibrosis (CF) gene. This hypothesis derives from previous work which has established the genetic commonality of CF and congenital bilateral absence of the vas deferens (CBAVD). Both CF and CBAVD may result from compound heterozygosity for CF mutations. In our patients with unilateral vasal aplasia, 12 had anatomically complete and patent vasa deferentia on the contralateral side, i.e. side of the scrotally palpable vas. No CF mutations were detected in this subgroup. The remaining nine patients had a non-iatrogenic occlusion of the contralateral vas at either the inguinal or pelvic level. In this subgroup, eight out of nine (89%) had a mutation detected in one of their two CF genes. This is the first study to define accurately the clinically and anatomically heterogeneous nature of CUAVD and to begin to clarify the genetic basis of unilateral absence of the vas deferens.