The majority of cases of Chlamydia-Induced reactive arthritis (CiReA) do not present with the classic triad of arthritis, conjunctivitis/iritis, and urethritis. Moreover, acute chlamydial infections are often asymptomatic. The aim of the present study was to assess the prevalence of synovial C. trachomatis (Ct) and C. pneumoniae (Cpn) infections in subjects with chronic undifferentiated spondyloarthritis (uSpA).
Study subjects met the European Spondyloarthropathy Study Group (ESSG) criteria without evidence of ankylosing spondylitis, psoriasis, inflammatory bowel disease, or preceding dysentery. Symptoms were present for at least 6 months. Data collected on the day of the test included standard demographics, history and physical examination (including joint count, evaluation for dactylitis and/or enthesitis, and skin exam), HLA-B27, history of Ct or Cpn. Each subject underwent synovial biopsy; tissue and concomitantly procured PBMC were analyzed by PCR for Ct and Cpn DNA. Synovial tissue from 167 subjects with osteoarthritis (OA) served as controls.
26 subjects met entry criteria and had a synovial biopsy (25 knee, 1 wrist). 16/26 (62%) were PCR-positive for either Ct or Cpn DNA, 10/16 (63%) for Ct, 4/16 (25%) for Cpn, 2/16 (13%) for both. These patients were significantly more likely to be PCR-positive compared to patients with OA (20/167 [12%]; p < 0.0001). No specific clinical characteristics differentiated PCR-positive from PCR-negative subjects. 4/26 (15%) subjects were PCR-positive in PBMC (3 Ct; 1 Cpn), 2 of which also were PCR-positive in synovial tissue (1 Ct; 1 Cpn). No significant correlation between PCR-positivity and HLA-B27-positivity was found.
The synovial tissue PCR-positivity rate in subjects with uSpA identified here is significantly higher than that found in the synovial tissue of subjects with OA. This result suggests that chlamydial infection, often occult, may be etiologic for uSpA in many patients.