The clinical spectrum of NFKB1 LOF includes massive lymphadenopathy (24%), unexplained splenomegaly (48%), and autoimmune disease (48%), either organ-specific and/or hematologic in nature (mainly autoimmune hemolytic anemia and idiopathic thrombocytopenic purpura, see Tables E1 and E2). The gene discussed is NFKB1; the disease is autoimmune thrombocytopenic purpura.