Ankylosing spondylitis and inflammatory bowel disease. III. Clinical characteristics and results of histocompatibility typing (HLA B27) in 50 patients with both ankylosing spondylitis and inflammatory bowel disease.

A study was made, in co-operation with several gastroenterology and rheumatology centres, of the clinical and genetic characteristics (HLA B27) of 50 patients suffering from both inflammatory bowel disease (38 Crohn's disease (CD), 12 ulcerated colitis (UC)) and ankylosing spondylitis (AS), the latter diagnosis being established according to the New York criteria. 20 CD (52.6%) and 8 UC (66.7%) patients were HLA B27 positive. The presence of HLA B27 was studied in relation to clinical parameters, such as first occurrence of symptoms of AS or inflammatory bowel disease (IBD), a history of peripheral arthritis, iridocyclitis, and a positive history of AS or IBD. Our patients were found to have heterogeneous clinical features: on one side of the spectrum a group of cases was distingiushed with the typical characteristics of idiopathic AS, often being HLA B27 positive. On the other side a smaller group of HLA B27 negative patients was observed, with severe intestinal inflammatory pathology, lacking most of the typical clinical features of idiopathic AS ('secondary' form of AS). Finally, between these two extremes a group of patients was found with less pronounced clinical or genetic characteristics. These different clinical and histocompatibility patterns suggest a mixed aetiopathogenesis of AS in IBD patients. Such a 'syndrome' of AS might harbour both idiopathic AS and forms of AS 'secondary' to the intestinal inflammatory pathology.