An important epigenetic phenomenon in macrophages is the transient inflammatory stimulus-mediated changes that include histone deacetylase (HDAC) activation, which increases the production of pro-inflammatory cytokines in wide disease models, including septic shock, acute respiratory distress syndrome, renal fibrosis, and rheumatoid arthritis, where abrogation of HDAC activity reduced inflammatory cytokines10–12. The gene discussed is HDAC9; the disease is rheumatoid arthritis.