HLA antigens in ankylosing spondylitis associated with Crohn's disease. Increased frequency of the HLA phenotype B27,B44.

In a consecutive case study 231 patients with Crohn's disease were investigated for ankylosing spondylitis (AS) and HLA-A, B, C, DR antigen association. Eighteen patients (7.8%) had definite AS according to the New York criteria; 13 (72%) were HLA-B27 positive. The phenotype B27,B44 was seen in 8 patients (44%) compared to only 3 (1%) of 300 controls (p less than 10(-7), and 1 (0.5%) of 213 patients with Crohn's disease without AS (p less than 10(-7). We conclude that patients with the phenotype B27,B44 are highly at risk (relative risk = 68.8) for the common manifestation of Crohn's disease and AS.