Genome-wide genetic association studies carried out with samples from multiple sclerosis (MS) and systemic lupus erythematosus (SLE) patients now provide evidence that genetically encoded changes of BAFF levels result in increased concentrations and correlate with the increased risk of developing autoimmunity (87).The genetic change results from a small deletion within the 3'UTR of BAFF mRNA. The gene discussed is TNFSF13B; the disease is myeloid sarcoma.