CFTR and cystic fibrosis: Additionally, Havasi et al. (2010) [90] stated that nearly 98% of men with cystic fibrosis also suffered from CBAVD and infertility, while in 80–97% of CBAVD cases the disease were caused by at least one defective CFTR allele and in 50–93% of cases they detected two abnormal CFTR variants.