RESUMO
IL-2-inducible T-cell kinase (ITK) deficiency is a rare inherited immunodeficiency disease characterized by homozygous mutations in the ITK gene and the inability to control Epstein-Barr virus (EBV) infection leading to EBV-associated lymphoproliferative disorders of B cell origin. Many aspects of its clinical presentation and immunologic phenotype are still unclear to clinicians. We report on a 14-year-old female patient with complaints of an 8-month history of cough and fever. Imaging studies revealed diffuse pulmonary nodules and mediastinal lymphadenopathy. Transbronchial lung biopsy showed nonmalignant polyclonal B cell proliferation. High titers of EBV DNA were detected by PCR analysis in bronchoalveolar lavage fluid, bone marrow, and blood. Genomic analysis revealed a homozygous single base pair deletion in exon 5 of the ITK gene (c.468delT) in this patient. Treatment with rituximab (anti-CD20 mab) resulted in complete clinical remission with resolution of pulmonary lesions and a negative EBV titer in serum. All patients with EBV-associated lymphoproliferative disorders should be analyzed for mutations in ITK.
Assuntos
Infecções por Vírus Epstein-Barr/enzimologia , Pneumonia Viral/enzimologia , Proteínas Tirosina Quinases/genética , Adolescente , Anticorpos Monoclonais Murinos/uso terapêutico , Linfócitos B/efeitos dos fármacos , Linfócitos B/patologia , Linfócitos B/virologia , Líquido da Lavagem Broncoalveolar/virologia , Tosse/diagnóstico , Tosse/tratamento farmacológico , Tosse/enzimologia , Tosse/patologia , Tosse/virologia , DNA Viral/análise , Infecções por Vírus Epstein-Barr/tratamento farmacológico , Infecções por Vírus Epstein-Barr/patologia , Feminino , Febre/diagnóstico , Febre/tratamento farmacológico , Febre/enzimologia , Febre/patologia , Febre/virologia , Humanos , Fatores Imunológicos/uso terapêutico , Pulmão/diagnóstico por imagem , Pulmão/efeitos dos fármacos , Pulmão/enzimologia , Pulmão/patologia , Pulmão/virologia , Ativação Linfocitária/efeitos dos fármacos , Ativação Linfocitária/genética , Transtornos Linfoproliferativos/diagnóstico por imagem , Transtornos Linfoproliferativos/tratamento farmacológico , Transtornos Linfoproliferativos/enzimologia , Transtornos Linfoproliferativos/patologia , Transtornos Linfoproliferativos/virologia , Pneumonia Viral/tratamento farmacológico , Pneumonia Viral/patologia , Mutação Puntual , Rituximab , Tomografia Computadorizada por Raios XRESUMO
The purpose of this study was the appraisal of the clinical and functional consequences of germline mutations within the gene for the IL-2 inducible T-cell kinase, ITK. Among patients with Epstein-Barr virus-driven lymphoproliferative disorders (EBV-LPD), negative for mutations in SH2D1A and XIAP (n=46), we identified two patients with R29H or D500T,F501L,M503X mutations, respectively. Human wild-type (wt) ITK, but none of the mutants, was able to rescue defective calcium flux in murine Itk(-/-) T cells. Pulse-chase experiments showed that ITK mutations lead to varying reductions of protein half-life from 25 to 69% as compared with wt ITK (107 min). The pleckstrin homology domain of wt ITK binds most prominently to phosphatidylinositol monophosphates (PI(3)P, PI(4)P, PI(5)P) and to lesser extend to its double or triple phosphorylated derivates (PIP2, PIP3), interactions which were dramatically reduced in the patient with the ITK(R29H) mutant. ITK mutations are distributed over the entire protein and include missense, nonsense and indel mutations, reminiscent of the situation in its sister kinase in B cells, Bruton's tyrosine kinase.