Similarly, for families with heterozygous pathogenic variants in FAS, incomplete penetrance of lymphoproliferation and autoimmunity can be partially explained by somatic changes in the second FAS allele in the lymphoid compartment (Magerus-Chatinet et al., 2011), consistent with models of multistep pathogenesis for malignant transformation (Goodnow, 2007). This evidence concerns the gene FAS and Autoimmunity.