title: Ultrasonographic assessment of enthesitis in HLA-B27 positive patients with rheumatoid arthritis, a matched case-only study.
abstract: BACKGROUND
  HLA-B27 has a modifier effect on the phenotype of multiple diseases, both associated and non-associated with it. Among these effects, an increased frequency of clinical enthesitis in patients with Rheumatoid Arthritis (RA) has been reported but never explored again. We aimed to replicate this study with a sensitive and quantitative assessment of enthesitis by using standardized ultrasonography (US).
  
  
  METHODS
  The Madrid Sonography Enthesitis Index (MASEI) was applied to the US assessment of 41 HLA-B27 positive and 41 matched HLA-B27 negative patients with longstanding RA. Clinical characteristics including explorations aimed to evaluate spondyloarthrtitis and laboratory tests were also done.
  
  
  RESULTS
  A significant degree of abnormalities in the entheses of the patients with RA were found, but the MASEI values, and each of its components including the Doppler signal, were similar in HLA-B27 positive and negative patients. An increase of the MASEI scores with age was identified. Differences in two clinical features were found: a lower prevalence of rheumatoid factor and a more common story of low back pain in the HLA-B27 positive patients than in the negative. The latter was accompanied by radiographic sacroiliitis in two HLA-B27 positive patients. No other differences were detected.
  
  
  CONCLUSIONS
  We have found that HLA-B27 positive patients with RA do not have more enthesitis as assessed with US than the patients lacking this HLA allele. However, HLA-B27 could be shaping the RA phenotype towards RF seronegativity and axial involvement.
authors.affiliation: Research Laboratory 10 and Rheumatology Unit, Instituto de Investigacion Sanitaria-Hospital Clinico Universitario de Santiago, Santiago de Compostela, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Mera-Varela
authors.forename: Aida
authors.initials: A
authors.lastname: Ferreiro-Iglesias
authors.forename: Eva
authors.initials: E
authors.lastname: Perez-Pampin
authors.forename: Marisol
authors.initials: M
authors.lastname: Porto-Silva
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Gómez-Reino
authors.forename: Antonio
authors.initials: A
authors.lastname: Gonzalez
mesh_terms: D000328:Adult; D001172:Arthritis, Rheumatoid / Q000000981:diagnostic imaging* / Q000235:genetics* / Q000378:metabolism; D005260:Female; D056726:Genetic Association Studies; D015796:HLA-B27 Antigen / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D014463:Ultrasonography
chemical_list: D015796:HLA-B27 Antigen