CTLA4 and infection: The clinical manifestations of PID are variable and include severe infections, autoimmunity and malignancies.1 PID conditions that are associated with autoimmune diseases due to defects in the regulation of self-tolerance are referred to as immune dysregulation diseases.2 Currently, several mutations leading to immune dysregulation, such as FOXP3 mutations causing immune dysregulation, polyendocrinopathy, enteropathy, or X-linked syndrome3 and cytotoxic T-lymphocyte-associated protein 4 (CTLA4) mutations resulting in CTLA4 haploinsufficiency,4,5 have been identified.