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Finnish HLA studies confirm the increased risk conferred by HLA-B27 homozygosity in ankylosing spondylitis
  1. E Jaakkola1,
  2. I Herzberg1,
  3. K Laiho3,
  4. M C N M Barnardo2,
  5. J J Pointon1,
  6. M Kauppi3,
  7. K Kaarela3,
  8. E Tuomilehto-Wolf4,
  9. J Tuomilehto4,
  10. B P Wordsworth1,
  11. M A Brown1
  1. 1Botnar Research Centre, Nuffield Orthopaedic Centre, Oxford, United Kingdom
  2. 2Transplant Centre, Churchill Hospital, Oxford, United Kingdom
  3. 3Rheumatism Foundation Hospital, Heinola, Finland
  4. 4National Public Health Institute, Helsinki, Finland
  1. Correspondence to:
    Dr Elisa Jaakkola
    Vaasa Central Hospital, Department of Internal Medicine, Hietalahdenkatu 2-4, 65130 Vaasa, Finland; elisa{at}


Objective: To determine the influence of HLA-B27 homozygosity and HLA-DRB1 alleles in the susceptibility to, and severity of, ankylosing spondylitis in a Finnish population.

Methods: 673 individuals from 261 families with ankylosing spondylitis were genotyped for HLA-DRB1 alleles and HLA-B27 heterozygosity/homozygosity. The frequencies of HLA-B27 homozygotes in probands from these families were compared with the expected number of HLA-B27 homozygotes in controls under Hardy–Weinberg equilibrium (HWE). The effect of HLA-DRB1 alleles was assessed using a logistic regression procedure conditioned on HLA-B27 and case–control analysis.

Results:HLA-B27 was detected in 93% of cases of ankylosing spondylitis. An overrepresentation of HLA-B27 homozygotes was noted in ankylosing spondylitis (11%) compared with the expected number of HLA-B27 homozygotes under HWE (4%) (odds ratio (OR) = 3.3 (95% confidence interval, 1.6 to 6.8), p = 0.002). HLA-B27 homozygosity was marginally associated with reduced BASDAI (HLA-B27 homozygotes, 4.5 (1.6); HLA-B27 heterozygotes, 5.4 (1.8) (mean (SD)), p = 0.05). Acute anterior uveitis (AAU) was present in significantly more HLA-B27 positive cases (50%) than HLA-B27 negative cases (16%) (OR = 5.4 (1.7 to 17), p<0.004). HLA-B27 positive cases had a lower average age of symptom onset (26.7 (8.0) years) compared with HLA-B27 negative cases (35.7 (11.2) years) (p<0.0001).

Conclusions:HLA-B27 homozygosity is associated with a moderately increased risk of ankylosing spondylitis compared with HLA-B27 heterozygosity. HLA-B27 positive cases had an earlier age of onset of ankylosing spondylitis than HLA-B27 negative cases and were more likely to develop AAU. HLA-DRB1 alleles may influence the age of symptom onset of ankylosing spondylitis.

  • AAU, acute anterior uveitis
  • BASDAI, Bath ankylosing spondylitis disease activity index
  • BASFI, Bath ankylosing spondylitis functional index
  • HWE, Hardy–Weinberg equilibrium
  • LD, linkage disequilibrium
  • MHC, major histocompatibility complex
  • QTDT, quantitative transmission disequilibrium test
  • ankylosing spondylitis
  • HLA-B27
  • homozygosity
  • HLA-DRB1

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