DEF6 and hyperinsulinemic hypoglycemia, familial, 4: Several clinical features, including the age of onset, degree of immunodeficiency, severity of the immune dysregulation phenotype with autoimmune and (fewer) autoinflammatory manifestations, and the risk of malignancy, have been investigated in relatively large cohorts of patients with CTLA-4 insufficiency and LRBA deficiency; and similar features have only been examined in two very small patient series with the newly discovered DEF6 deficiency most recently (5–7, 9, 10, 16, 17).