Given the evidence of a role of variation in the IL2RA/CD25 gene in autoimmune disease susceptibility provided by the genome-wide association studies of MS and RA and the fine-mapping of the IL2RA/CD25 region in type 1 DM, we hypothesized that IL2RA/CD25 may also play a role in JIA. Here, IL2RA is linked to myeloid sarcoma.