Among the NK cell deficiencies that are associated with EBV-positive lymphomas and EBV-driven immunopathologies such as hemophagocytic lymphohistiocytosis (HLH) are mutations in the minichromosome maintenance complex component 4 (MCM4) or interferon regulatory factor 8 (IRF8) [32,33,34]. The gene discussed is MCM4; the disease is hemophagocytic syndrome.