Clinical trials of neutralizing antibodies targeting IL-17 and IL-17RA in patients with Crohn’s disease have shown that disease worsening has been observed in patients treated with sukinumab (anti-IL-17) (214) and increased serum C-reactive protein, an indicator of inflammation, has been observed in patients treated with brodalumab (anti-IL-17RA) (215). This evidence concerns the gene IL17A and Crohn disease.