Boys, sometimes fatal immune disorders that occur after EBV infection with two X chromosomes encoding gene mutation chain, these two genes SLAM-associated protein (SAP) and X - linked inhibitor of apoptosis protein (XIAPprotein). In this study, we describe two girls in a Turkish family in EBV infection, severe immune disorders and ineffective treatment of EBV-positive B-cell proliferation, and ultimately death. SNP array-based genome-wide linkage analysis showed that IL - 2-inducible T cell protein kinase (ITK) this immunodeficiency syndrome candidate gene. Two girls contain homozygous missense mutation, resulting in the ITK highly conserved residues of the SH2 domain (R335W) substitution mutation occurs. Observed in any one or both girls mouse model ITK characteristics of defects, such as lack of NKT cells and CD8 + cells, a high level of eomesodermin. Two evidence that the R335W caused ITK protein instability. First, the mutant proteins silicon simulation predicts the the SH2 domains instability. In addition, Western blot analysis showed that the wild-type ITK, R335W mutation expressed in 293 T cells, almost undetectable. Our experimental results show that the ITK defects result we consider a novel immunodeficiency syndrome, which in turn led to the fatal deficiencies EB virus immune response. Boys, ITK deficiency similar to the EB virus-associated lymphoproliferative disease, we propose, should be considered in the diagnosis and treatment of the cause of this molecule.