CFTR and congenital bilateral aplasia of vas deferens from CFTR mutation: CF is also characterized by pancreatic insufficiency (PI) – probably due to the important role that CFTR also plays in bicarbonate secretion – elevated levels of chloride in the sweat – where the lack of functional CFTR blocks NaCl reabsorption (which are coupled in this tight epithelium, differing from the airways) – meconium ileus, low body mass index (BMI), infertility in men mostly because of bilateral absence of vas deferens (CBAVD), and undescended testicles or hydrocele, amenorrhea in women and severe nutritional involvement [3,9,10].