The role of TNFAIP3 in development is highlighted by the fact that haploinsufficiency of TNFAIP3 causes a rare autoinflammatory disease (HA20), and TNFAIP3 is critical for the development of monocyte derived cells in lymphoid organ and of microglia in the central nervous system (31, 32). The gene discussed is TNFAIP3; the disease is A20 haploinsufficiency.