IL1RN and chronic recurrent multifocal osteomyelitis: Although the etiology of chronic non-bacterial osteomyelitis is still unknown, deficiency of IL-1β receptor antagonist and neonatal-onset multisystem inflammatory disease are caused by mutations in the IL1RN and NLRP3 genes, respectively, and result in over-activation of the IL-1β pathway (Morbach et al., 2013).