A definitive diagnosis of ALPS requires (1) the presence of chronic lymphadenopathy and/or splenomegaly which cannot be attributed to infection or malignancy, (2) elevated CD4/CD8 double negative alfa-beta (DN) T cells in the peripheral blood and (3) either the demonstration of a mutation associated with ALPS or the demonstration of defective apoptosis with functional assays [8]. Here, CD4 is linked to autoimmune lymphoproliferative syndrome.