Isoprenoids are implicated in several biochemical pathways, and one of their functions is the posttranslational modification of small G proteins involved in the inflammatory response: it has been demonstrated that peripheral blood mononuclear cells from patients with HIDS have a limited pool of isoprenoids available and show a decreased Rho GTPase activity: as a consequence, sustained activation of Rac1 (a small GTPase) and increased IL-1β production can be observed [123]. Here, IL1B is linked to hyperimmunoglobulinemia D with periodic fever.