Chlamydia pneumoniae as a triggering infection in reactive arthritis.

OBJECTIVE: To determine the role of Chlamydia pneumoniae as a triggering infection in reactive arthritis (ReA). METHODS: Sixty patients with acute arthritis were screened for the evidence of triggering infections. In all patients, bacterial stool cultures, culture of Chlamydia trachomatis in urethra/cervix, and/or bacterial serology were studied. Chlamydia pneumoniae antibodies were measured by specific microimmunofluorescence test. RESULTS: Thirty-five of 60 patients fulfilled the diagnostic criteria for ReA. Thirty-one patients had microbial/serological evidence of preceding infection due to Salmonella, Yersinia, Campylobacter or Chlamydia trachomatis, or they had enteritis or urethritis prior to arthritis. Four additional patients had high antibody titre for C. pneumoniae. Three of these four patients had preceding lower respiratory symptoms, and were positive for HLA-B27. The clinical picture of C. pneumoniae-positive ReA patients was similar to that of ReA patients with other definite aetiology. CONCLUSION: Chlamydia pneumoniae is a triggering factor in approximately 10% of patients with acute ReA.