Finally, similar to other IEIs characterized by failed control of EBV, such as the IL-2-inducible T Cell kinase (ITK) deficiency or the X-linked immunodeficiency with magnesium defect, EBV infection and neoplasia (XMEN) syndrome, autoimmunity in TET2 deficiency manifests primarily with autoimmune cytopenias.11 Here, TET2 is linked to hyperinsulinemic hypoglycemia, familial, 4.