Idiopathic CD4+ T lymphocytopenia (ICL) is a rare syndrome, defined in 1992 as: (1) absolute CD4+ T lymphocyte level <300cells/μL or <20% of total lymphocytes at a minimum of two separate time points at least six weeks apart; (2) no serological evidence of human immunodeficiency virus (HIV) infection; (3) the absence of any defined immunodeficiency or therapy associated with depressed levels of CD4+ T cells[8,9]. This evidence concerns the gene CD4 and Immunodeficiency.