Functional CTLA4 deficiency, whether due to CTLA4 haploinsufficiency, LRBA deficiency or DEF6 deficiency, may be suspected in cases with lymphoproliferation (38–73%) and granulomatous disorders (17–45%) associated with complex autoimmunity (mainly cytopenias) and inflammatory enteropathy. The gene discussed is CTLA4; the disease is Autoimmunity.