Infertility in cystic fibrosis

I believe it is from a gene mutation

I think 50-80% of patients with Congenital Bilateral Absence of the Vas Deferens (CBAVD) have at least one known CFTR gene mutation, in the 508 region. And that approximately 10% have two known CFTR mutations. Most men with CBAVD have only one detectable gene mutation or variant.

Yes, absent tubes

Yes, as Peewee said the mechanism of male infertility in CF patients is bilateral absence of the vas deferens. That's so common an association to the extent that males with infertility due to this defect should be screened for CF (in case it's mild and not diagnosed).

However, please remember that although these patients are infertile but they are not sterile. They make sperms but they are missing the tubes. So taking the sperms and doing Intra Uterine Insemination will solve their infertility.