Although TGF-β level is thought to be an independent factor related to the occurrence of chronic HBV infection (CHB) [239], serum TGF-β1 and IL-31 were markedly higher in HBV-related liver cirrhosis (LC) patients and correlated with the severity of HBV-LC, suggesting possible roles of the TGF-β1/IL-31 pathway in the pathogenesis of liver fibrosis during CHB [237,240]. This evidence concerns the gene TGFB1 and laryngotracheoesophageal cleft.