title: Occurrence of ankylosing spondylitis in a nationwide series of twins.
abstract: 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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Rheumatism Foundation Hospital, Heinola, Finland.
authors.forename: P
authors.initials: P
authors.lastname: Järvinen
mesh_terms: D000328:Adult; D000368:Aged; D015331:Cohort Studies; D004200:Diseases in Twins / Q000175:diagnosis / Q000453:epidemiology* / Q000235:genetics; D005260:Female; D005387:Finland / Q000453:epidemiology; D005819:Genetic Markers; D015796:HLA-B27 Antigen / Q000032:analysis*; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D012042:Registries; D013167:Spondylitis, Ankylosing / Q000175:diagnosis / Q000453:epidemiology* / Q000235:genetics; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic
chemical_list: D005819:Genetic Markers; D015796:HLA-B27 Antigen