The correlation between the presence of HLA-B27 and ankylosing spondylitis has been a known entity since the early 1970s.  Although common in the general population, this allele strongly contributes to the susceptibility of development of the linked family of inflammatory rheumatologic conditions collectively known as spondyloarthritis. Additional associated diseases, particularly acute anterior uveitis, are also highly correlated with possession of HLA-B27. Although associated with spondyloarthritis, the pathologic role of this allele in immune dysregulation remains under investigation. With lower frequency, the presence of the HLA-B27 allele has correlated with inflammatory bowel disease, psoriatic arthritis, and reactive arthritis.