CTLA4 and agammaglobulinemia: In fact, and while the latest International Union of Immunological Societies Expert Committee Classification of Human Inborn Errors of Immunity Update included APDS-1 in IEI characterized by predominantly antibody deficiency [34], our cohort’s phenotype overlaps more with other IEI belonging to the group of immune dysregulation, such as the aforementioned CTLA-4 haploinsufficiency, LRBA deficiency or the autoimmune lymphoproliferative syndrome group.