CFTR and congenital bilateral aplasia of vas deferens from CFTR mutation: Cystic fibrosis transmembrane conductance regulator (CFTR) gene mutation is the first to be found to be related to CBAVD, and this mutation is considered to be the main causal entity in the occurrence of CBAVD (Kerem et al., 1989; Rommens et al., 1989).