For example, autoimmune lymphoproliferative syndrome can arise from somatic mutations in TNFRSF6, KRAS, or NRAS. Certain mutations in TNFRSF6, which encodes the Fas receptor, in the lymphoid lineage have a dominant negative effect that allows increased survival and lymphoproliferation mimicking the phenotype of germline TNFRSF6 mutations (32, 33). The gene discussed is FAS; the disease is autoimmune lymphoproliferative syndrome.