STAT3 and activated PI3K-delta syndrome: The ESID-APDS registry analysis found APDS to have the highest rates of lymphoproliferation compared to the clinically similar autoimmune lymphoproliferative IEIs Cytotoxic T-lymphocyte associated protein 4 (CTLA-4) haploinsufficiency, Signal transducer and activator of transcription 3 (STAT3) gain-of-function and Nuclear Factor Kappa B Subunit 1(NFkB1) deficiency (15).