Autoimmune lymphoproliferative syndrome is a rare entity resulting from mutations in several genes related to the apopotosis pathways including Fas, Fas ligand, caspase 8 and caspase 10. It is an autosomal dominant disease and majority of these case present with lymphocytosis, organomegaly, hypergammaglobulinemia and autoimmune cytopenias.

A diagnostic feature is the presence of distinct expanded CD4 -/CD8 - TCRalpa/beta subset of T-cells. This T-cell subset exhibits impaired proliferative and cytokine response to activation.