CD40LG and biliary tract cancer: Mutations in the CD40L gene cause X-linked immunodeficiency with hyperimmunoglobulin M. In the case of CD40L and CD40 ligand deficiencies, a Cryptosporidium biliary tract infection may lead to sclerosing cholangitis, cirrhosis, and an increased risk of hepatocellular carcinoma and biliary tract cancer [121,122,123].