CFTR and cystic fibrosis: Examples are renal tubular acidosis, congenital chloride diarrhoea, Pendred syndrome, glaucoma, and various blood disorders.[7, 10, 11, 14] Altered expression patterns of HCO3− transporters have been observed in many types of cancer as well.[16] Many symptoms of the congenital disease cystic fibrosis (CF), primarily associated with deficient Cl− transport by CFTR, are also caused by a lack of HCO3− crossing epithelial cell membranes.[12, 17, 18]