What HLA occurs more commonly than expected with IBD associated Spondyloarthritis?
HLA-B27. Of a normal healthy Caucasian population, 8% has the HLA-B27 gene, but a patient with IBD who possesses the HLA-B27 gene has a 7 to 10 times increased risk of developing an inflammatory sacroiliitis/ spondylitis compared with IBD patients who are HLA-B27-negative. It should be noted that the mutation of NOD2 (CARD15) gene on chromosome 16 that has been associated with the development of Crohn’s disease has not been associated with an increased prevalence of axial or peripheral inflammatory arthritis in patients with IBD.