Beyond its role in B-cell intrinsic processes, NF-κB1 defects presenting with recurrent or chronic Epstein–Barr virus (EBV) infection (6, 8) or fatal EBV-driven lymphoproliferative disease (7) suggest a broadened phenotypic spectrum, including combined immunodeficiency (CID) with B- and T-cell dysfunction (7). The gene discussed is NFKB1; the disease is severe combined immunodeficiency.