Identification of ITK deficiency as a novel genetic cause of idiopathic CD4+ T-cell lymphopenia

摘要

Idiopathic CD4 lymphopenia represents a heterogeneous group of combined primary immunodeficiencies with markedly reduced CD4+ T-cell counts. Although several genetic etiologies including MHC class II deficiency1 or mutations in RAG1, MST1, or LCK have been reported, the majority of patients remain genetically undetermined. Here we describe a 17-year-old male Turkish patient of consanguineous background, referred to the hospital at 7 years of age. He suffered from recurrent pulmonary infections causing progressive immune reaction and bronchiectasia. Immunological analysis at the age of 10 showed persistently low CD4+ T-cell counts (range: 8% to 16%; 286-714/|xL) and increased CD8+ T-cell counts (range: 50% to 59%; 1404-2950/fjiL, Figure 1 A). T-cell proliferation responses to CD3/CD28 stimulation were reduced (not shown), whereas PHA stimulation led to normal proliferation of T-cells. B-cell counts and immunoglobulin levels were unremarkable (not shown); however, the patient showed reduced antipneumococcal antibody response.