Cystic Fibrosis (CF) is a progressive autosomal recessive disorder caused by defects in the cystic fibrosis transmembrane conductance regulator gene (CFTR). CFTR mutations cause loss or impairment of CFTR-mediated ion transport across epithelial cell membranes. CF affects many organs including the respiratory tract, pancreas, intestine, liver and the male reproductive tract. Liver disease occurs less frequently than pulmonary disease. CFTR is expressed in the bile duct epithelial cells and is responsible for the hydration of biliary secretions.

CF was until recently, thought to be a multi-organ disease. However, there are now recognized non-classical presentations of CF involving a few organs only and now there is well established data on single -organ involvement including Congenital Absence of the Vas Deferens and recurrent pancreatitis.

CF and PSC have several features in common. They both affect intrahepatic bile ducts by inspisated biliary secretions, chronic inflammation and fibrosis. Is PSC the "single-organ presentation" of CF? Patients with PSC will undergo testing of the CF protein channel by nasal potential testing. This test is performed by insering a thin plastic tube 2 to 3 cms into the nostril and chloride transport can be measured. This test may shows that the patient has an abnormality in the CF protein channel.