FAS and autoimmune lymphoproliferative syndrome: In ALPS-FAS, the impaired apoptosis and the consequent expansion of specific subsets of lymphocytes (4) (i.e., total CD3+ T-cells, CD3+CD8+ T-cells, CD3+TCRαβ+CD4−CD8− double negative T-cells, CD5+CD20+ B-cells), including self-antigen reactive subpopulations, results in specific clinical manifestations and laboratory abnormalities such as lymphadenopathy, hepatomegaly, splenomegaly, autoimmune hemolytic anemia, thrombocytopenia, and neutropenia (5, 6).