Primary immunodeficiencies are a heterogeneous group of hereditary diseases that are associated with compromised immune responses. There are a number of immunodeficiencies resulting in inability of immune system to control EBV infection, for example X-linked Lymphoproliferative disease (XLP)/SAP deficiency, X-linked inhibitor of apoptosis (XIAP) deficiency, CD27 deficiency, ITK deficiency, and so on. Whereas, some other clinical states associated with EBV-susceptibility remain largely unknown. Rare EBV-infected individuals without apprent immunodeficiency also present with persistent IM-like symptoms, hepatosplenomegaly, liver dysfunction, lymphadenopathy and haemophagocytic lymphohistiocytosis.