For example, we analyzed some putative modifier genes of liver cystic fibrosis phenotype like hemochromatosis, transferrin receptor 2, ferroportin 1, mannose binding lectin (MBL), and adenosine triphosphate-binding cassette subfamily B member 4 (ABCB4) in 108 unrelated CF patients with and without liver involvement. The gene discussed is ABCB4; the disease is cystic fibrosis.