Recent advances and future directions in understanding and treating Chlamydia-induced reactive arthritis

INTRODUCTION

Reactive arthritis (ReA) is an inflammatory disease that can follow gastrointestinal or genitourinary infections. The primary etiologic agent for post-venereal ReA is the bacterium Chlamydia trachomatis; its relative, C pneumoniae, has also been implicated in disease induction although to a lesser degree. Studies have indicated that the arthritis is elicited by chlamydiae infecting synovial tissue in an unusual biologic state designated persistence. We review clinical aspects, host-pathogen interactions, and treatments for the disease. Areas covered: We briefly discuss both the historic and,more extensively, the current medical literature describing ReA, and we provide a discussion of the biology of the chlamydiae as it relates to elicitation of the disease. A summary of clinical aspects of Chlamydia-induced ReA is included to give context for approaches to treatment of the arthritis. Expert commentary: Basic research into the biology and host-pathogen interactions characteristic of C trachomatis has provided a wealth of information that underlies our current understanding of the pathogenic processes occurring in the ReA synovium. Importantly, a promising approach to cure of the disease is at hand. However, both basic and clinical research into Chlamydia-induced ReA has lagged over the last 5 years, including required studies relating to cure of the disease.

[Chlamydia-associated arthritis and enteropathic arthritis--two important spondyloarthritides]

Spondyloarthritis (SpA) includes reactive arthritis (ReA) and enteropathic arthritis (EA), which are clinically important but often misdiagnosed. ReA, sterile inflammatory arthritis, arises after certain genitourinary or gastrointestinal infections. Chlamydia are the most common pathogens causing ReA; ReA due to Chlamydia infection is called Chlamydia-associated arthritis (Chl-AA). Recently, Chlamydia trachomatis was detected in the synovial tissue from patients with ReA by electronmicroscopy. In addition, mRNA as well as DNA has been detected in the synovial tissue, suggesting that Chlamydia are viable in inflamed joints. Thus, the notion that ReA is a sterile inflammation should be reconsidered. Chl-AA patients, especially women, often show no symptoms and signs of genitourinary infection. Thus, Chl-AA should be suspected in patients with inflammatory arthritides that is difficult to diagnose. EA is accompanied by inflammatory bowel diseases (IBD). In Japan, over 130,000 individuals have IBD; IBD is diagnosed in 6,500 individuals every year. Around 10% IBD patients develop arthritis, suggesting that 13,000 patients develop arthritis every year. SpA includes peripheral and axial arthritis; axial arthritis includes spondylitis and sacroiliac arthritis. Sacroiliac joint tests need to be performed to diagnose sacroiliac arthritis. Rheumatologists should be aware of the pathogenesis of Chl-AA and EA and diagnose and treat these diseases appropriately.