CFTR and congenital bilateral absence of vas deferens: (1) Introduction: Pathogenic variants in the CFTR (Cystic Fibrosis Transmembrane conductance Regulator, OMIM: 602421) gene cause Cystic Fibrosis (CF, OMIM: 219700) and CF-related disorders (CF-RD), often accompanied by obstructive azoospermia due to congenital bilateral aplasia of vas deferens (CBAVD, OMIM: 277180) in male patients.