It has been suggested that subclinical intestinal inflammation plays a pathogenic role in ankylosing spondylitis (AS). I. Bjarnason I and fellow researchers assessed the possible presence and inheritance pattern of subclinical intestinal inflammation in first-degree relatives of patients with AS.

Since the majority of people with AS test positive for the HLA-B27 gene, they also studied the relationship between intestinal inflammation and the subjects’ HLA-B27 genotype. Researchers sought to study a third item – computerized tomographic (CT) abnormalities in the sacroiliac joints – as it is a hallmark symptom of AS.

Participants
A total of 124 of 213 (58%) available first-degree relatives of 47 patients with AS in Iceland underwent investigation for intestinal inflammation (fecal calprotectin concentration), HLA-B27 genotyping and CT of the sacroiliac joints.

Results
Forty-one percent of the first-degree relatives had subclinical intestinal inflammation, whereas 15 of 17 spouses were normal. This suggests that a major additive gene affects the inheritance of this pattern of inflammation.

Some sacroiliac changes, suggestive of early AS, differed significantly between subjects with and without subclinical intestinal inflammation.

Intestinal inflammation and sacroiliac changes did not relate to the subjects’ HLA-B27 status.

Conclusion
Many first-degree relatives of patients with AS appear to have an inherited abnormality that leads to subclinical intestinal inflammation. The association between the presence of this inflammation and the sacroiliac changes suggests that it may play a pathogenic role in AS.