title: Subclinical intestinal inflammation and sacroiliac changes in relatives of patients with ankylosing spondylitis.
abstract: OBJECTIVE
  It has been suggested that subclinical intestinal inflammation plays a pathogenic role in the spondylarthropathy of ankylosing spondylitis (AS). We assessed the possible presence and inheritance pattern of subclinical intestinal inflammation in first-degree relatives of patients with AS. The relationship between this inflammation and the subjects' HLA-B27 genotype as well as computerized tomographic sacroiliac abnormalities was also assessed.
  
  
  METHODS
  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 computerized tomography of the sacroiliac joints.
  
  
  RESULTS
  A total of 41% of the first-degree relatives had subclinical intestinal inflammation, whereas 15 of 17 spouses were normal. Variance components analyses suggest that the inheritance pattern of this inflammation is affected by a major additive gene. Some sacroiliac changes, suggestive of early AS, differed significantly between subjects with and without subclinical intestinal inflammation (mean diameter of subchondral cysts [2.9 vs. 1.2 mm; P = 0.026] and blurring of joint margins [9 of 44 (20%) vs. 1 of 41 (2%); P = 0.02]). Intestinal inflammation and sacroiliac changes did not relate to the subjects' HLA-B27 status.
  
  
  CONCLUSIONS
  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 the spondylarthropathy of AS.
authors.affiliation: Department of Medicine, Guy's, King's, St. Thomas' Medical School, London, England. ingvar.bjarnson@kcl.ac.uk
authors.forename: Ingvar
authors.initials: I
authors.lastname: Bjarnason
authors.forename: Kristjan O
authors.initials: KO
authors.lastname: Helgason
authors.forename: Arni J
authors.initials: AJ
authors.lastname: Geirsson
authors.forename: Gudmundur
authors.initials: G
authors.lastname: Sigthorsson
authors.forename: Inga
authors.initials: I
authors.lastname: Reynisdottir
authors.forename: Daniel
authors.initials: D
authors.lastname: Gudbjartsson
authors.forename: Anna S
authors.initials: AS
authors.lastname: Einarsdottir
authors.forename: Roy
authors.initials: R
authors.lastname: Sherwood
authors.forename: Kristleifur
authors.initials: K
authors.lastname: Kristjansson
authors.forename: Olafur
authors.initials: O
authors.lastname: Kjartansson
authors.forename: Bjarni
authors.initials: B
authors.lastname: Thjodleifsson
mesh_terms: D000328:Adult; D003424:Crohn Disease / Q000209:etiology / Q000235:genetics; D004751:Enteritis / Q000235:genetics*; D005260:Female; D005838:Genotype; D015796:HLA-B27 Antigen / Q000235:genetics*; D006801:Humans; D039841:Leukocyte L1 Antigen Complex / Q000032:analysis; D008297:Male; D008875:Middle Aged; D012446:Sacroiliac Joint / Q000000981:diagnostic imaging*; D013167:Spondylitis, Ankylosing / Q000235:genetics*; D014057:Tomography, X-Ray Computed
chemical_list: D015796:HLA-B27 Antigen; D039841:Leukocyte L1 Antigen Complex