The broad functionality of CD40 on immune responses, coupled with its critical role in several experimental autoimmune conditions, such as collagen induced arthritis [8], experimental Graves' disease [9], experimental autoimmune encephalomyelitis (EAE), a model of multiple sclerosis (MS) [10], lupus nephritis [11] and type 1 diabetes [12] suggest its association with other immune-mediated diseases. This evidence concerns the gene CD40 and myeloid sarcoma.