HLA B27 in regional enteritis with and without ankylosing spondylitis or sacroiliitis.

The incidence of B27 in patients with ankylosing spondylitis associated with regional enteritis was significantly lower than in ankylosing spondylitis without inflammatory bowel disease. It was significantly higher, however, than in a control group of blood donors. The incidence of B27 was found to be nil in patients with regional entertitis without ankylosing spondylitis, as well as in patients with regional enteritis and asymptomatic radiographic sacroilitis. Conversely, all patients with regional enteritis, positive for B27, developed ankylosing spondylitis.