IL21 and Behcet disease: In pediatric patients with early onset and multi-system involvement, the possibility of monogenic Behçet’s disease and a board range of inborn errors of immunity should be strongly considered, including chronic granulomatous disease, A20 haploinsufficiency, NEMO deficiency, IL21 deficiency, IL10 deficiency, IL10R deficiency, ELF4 deficiency, NFAT5 haploinsufficiency, TGFB1 deficiency, and others (16–20).