Although controversial results have been reported on the increase or decrease of MUC5AC and MUC5B due to various methods of assessing mucin, there is no doubt that the pathophysiology of cystic fibrosis (CF) is related to the viscous mucus secreted from the epithelial surface of the respiratory and intestinal tract [27, 28]. This evidence concerns the gene MUC5B and cystic fibrosis.