This heterogeneous group encompasses syndromes of early-onset polyautoimmunity, such as immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome and LPS-Responsive Beige-Like Anchor protein (LRBA) deficiency, as well as conditions characterized by other forms of immune dysregulation, including chronic lymphoproliferation (e.g., X-linked lymphoproliferative syndrome) and hemophagocytic lymphohistiocytosis (HLH), encompassing familial HLH and Chediak–Higashi syndrome (2). The gene discussed is LRBA; the disease is X-linked lymphoproliferative disease.