Polymorphisms in endoplasmic reticulum aminopeptidase 1 (ERAP1) have been linked to several important autoimmune diseases such as Ankylosing Spondylitis (AS), Type I diabetes, Multiple Sclerosis, and Behçet's disease, suggesting that causation of these conditions may share a common mechanism due to dysfunctions in ERAP1 [1]. The gene discussed is ERAP1; the disease is autoimmune disease.