Considering clinical characteristics, some studies have demonstrated that, in CD patients, young age, isolated colitis, and elevated CRP levels are predictors of response to anti-TNF therapy, while smoking and disease duration more than 2 years are predictors of non-responders (Louis et al., 2002; Parsi et al., 2002; Arnott et al., 2003; Siegel and Melmed, 2009). This evidence concerns the gene TNF and colitis.