XIAP deficiency was first described in 2006 and is associated with a variety of disease manifestations, including recurrent haemophagocytic lymphohistiocytosis (HLH), inflammatory bowel disease (IBD), hypogammaglobulinemia, severe and/or recurrent infections, splenomegaly, and cytopaenias (2–4). Here, XIAP is linked to hyperinsulinemic hypoglycemia, familial, 4.