Occurrence of ankylosing spondylitis in a nationwide series of twins

Arthritis Rheum. 1995 Mar;38(3):381-3. doi: 10.1002/art.1780380313.


Objective: To obtain information on the rate of concordance for ankylosing spondylitis (AS) in a population-based series of twins.

Methods: AS cases were identified by record linkage of the population-based Finnish Twin Cohort and the nationwide registry for fully reimbursed medications. A clinical examination was performed to establish concordance for AS.

Results: There were 6 monozygotic (MZ) pairs and 20 dizygotic (DZ) pairs with at least 1 member affected by AS. Three MZ pairs and 3 DZ pairs were concordant for the disease. All affected subjects were HLA-B27 positive. The pairwise concordance rate was 50% in MZ twins and 20% in HLA-B27 positive DZ twins (95% confidence intervals 11.8-88.2% and 4.3%-48.1%, respectively).

Conclusion: These results indicate that AS disease expression is largely, but not entirely, genetically based, with a gene or genes other than B27 probably playing a role.

Publication types

  • Research Support, Non-U.S. Gov't
  • Twin Study

MeSH terms

  • Adult
  • Aged
  • Cohort Studies
  • Diseases in Twins / diagnosis
  • Diseases in Twins / epidemiology*
  • Diseases in Twins / genetics
  • Female
  • Finland / epidemiology
  • Genetic Markers
  • HLA-B27 Antigen / analysis*
  • Humans
  • Incidence
  • Male
  • Middle Aged
  • Registries
  • Spondylitis, Ankylosing / diagnosis
  • Spondylitis, Ankylosing / epidemiology*
  • Spondylitis, Ankylosing / genetics
  • Twins, Dizygotic
  • Twins, Monozygotic


  • Genetic Markers
  • HLA-B27 Antigen