FAS and autoimmune lymphoproliferative syndrome: The lack of any evidence supporting reduced thymic output or altered T-cells peripheral homeostasis along with a homogenous loss of CD4 T-cells of either naïve or memory phenotype in a disease typically associated with accumulation of autoreactive T cells and autoimmune phenomena, led us to consider an autoimmune pathogenesis for the reduced CD4 T-cells observed in some patients with ALPS-FAS.