title: Reactive arthritis: incidence, triggering agents and clinical presentation.
abstract: OBJECTIVE
  To study the incidence and presenting clinical and microbiological features in subgroups of reactive arthritides.
  
  
  METHODS
  In a defined community and during a 2-year period, we studied prospectively patients between 18 and 60 years with onset of suspected reactive arthritis, primarily seen by general practitioners.
  
  
  RESULTS
  Annual minimum incidence of Chlamydia induced arthritis (n = 25) was 4.6 and of arthritis triggered by enterobacteria (n = 27) 5.0/100,000 individuals between 18 and 60 years. Triggering infections were asymptomatic in 36 and 26%, respectively. Patients with self-limiting arthritis without identified triggering agents (n = 60, incidence 11.0/100,000) had a normal prevalence of HLA-B27 and a more heterogeneous pattern of arthritis.
  
  
  CONCLUSIONS
  Our epidemiological study confirms suggested high incidence rates of reactive arthritides. Reactive arthritides must be considered in early arthritis, even without symptoms of triggering infections.
authors.affiliation: Oslo City Department of Rheumatology, Norwegian Lutheran Hospital.
authors.forename: T K
authors.initials: TK
authors.lastname: Kvien
authors.forename: A
authors.initials: A
authors.lastname: Glennås
authors.forename: K
authors.initials: K
authors.lastname: Melby
authors.forename: K
authors.initials: K
authors.lastname: Granfors
authors.forename: O
authors.initials: O
authors.lastname: Andrup
authors.forename: B
authors.initials: B
authors.lastname: Karstensen
authors.forename: J E
authors.initials: JE
authors.lastname: Thoen
mesh_terms: D000293:Adolescent; D000328:Adult; D016918:Arthritis, Reactive / Q000453:epidemiology* / Q000276:immunology / Q000382:microbiology*; D002689:Chlamydia; D004756:Enterobacteriaceae Infections; D005260:Female; D015796:HLA-B27 Antigen / Q000032:analysis; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D012621:Seasons; D013548:Sweden
chemical_list: D015796:HLA-B27 Antigen