TAMPA, Florida—Undiagnosed but persistent chlamydial infections might cause most cases of undifferentiated spondylarthritis (uSpA), and physicians should not expect patients to have the classic triad of uveitis/iritis, urethritis, and arthritis, or to be HLA-B27 positive. These conclusions are reported by John D. Carter, MD, and colleagues in Arthritis & Rheumatism.1 Dr. Carter is at the University of South Florida College of Medicine in Tampa, Florida.

“Our results suggest that in many patients with uSpA, chlamydial infection, which is often occult, may be the cause.”—John D. Carter, MD
”Patients with uSpA were significantly more likely to have synovial tissue positive for chlamydia than patients with osteoarthritis (OA). Furthermore, only a very small fraction of the subjects who were PCR-positive for chlamydiae in their synovial tissue had a history of a known chlamydial infection. Silent or asymptomatic chlamydial infections appear to be a common cause of the resultant arthritis (uSpA or reactive arthritis, ReA). Clinicians should not rely on a history of a chlamydial infection in order to diagnose Chlamydia-induced arthritis. Remember, a large percentage of acute C. trachomatis infections are asymptomatic,” Dr. Carter told MSKreport.com.

This study included 26 patients drawn from 80 screened as part of a clinical trial of an antibiotic treatment for Chlamydia-induced ReA. Synovial biopsies from these 26 patients were compared to biopsies from a control group of 167 patients with osteoarthritis (OA).

The researchers found that:
  • 16 of 26 uSpA patients (62%) were positive for C. trachomatis and/or C. pneumoniae DNA vs. only 20 of 167 OA controls (12%, P<.0001)
  • no specific clinical characteristics differentiated uSpA patients with vs. without chlamydia infection
  • no significant correlation between Chlamydia positivity and HLA-B27 positivity

“Our results suggest that in many patients with uSpA, chlamydial infection, which is often occult, may be the cause,” the authors concluded.

Chlamydia and arthritis: Translating research into practice

Dr. Carter said that there is still considerable uncertainty about how to apply this information in clinical practice.

“It is probably not practical to perform a synovial biopsy on most uSpA patients in a clinical setting. We know that when a patient acquires an acute C. trachomatis infection, the organism is capable of disseminating to distant sites such as the synovium, but current data suggests that routine genital testing for the organism is often negative after dissemination. Therefore, a negative genital test does not preclude the diagnosis of Chlamydia-induced arthritis. We really need a minimally invasive diagnostic test for Chlamydia-induced arthritis. Unfortunately one doesn’t exist at this time,” Dr. Carter said.

Ordering up a round of empirical antibiotic therapy is also questionable.

“Acute and persistent chlamydial infections are two very different entities,” Dr. Carter explained. “Whenever these organisms disseminate to distant sites (e.g. synovium), they enter a phase called 'persistence.' The organisms are still viable, but their life cycle is attenuated and aberrant. Acute chlamydial infections are very susceptible to antimicrobial therapy, but the utility of antibiotics in persistent chlamydial infections is unknown.”

However, Dr. Carter advised clinicians to “stay tuned,” since the data in this paper were baseline data from a clinical trial assessing long-term combination antibiotics as a potential treatment for chronic Chlamydia-induced arthritis.

Reference

1. Carter JD, Gerard HC, Espinoza LR, et al. Chlamydiae as etiologic agents in chronic undifferentiated spondylarthritis. Arthritis Rheum. 2009;60:1311-1316.