Reactive Arthritis in Young Military Personnel: A Prospective Study on Epidemiology, Clinical Presentation, and Genetic Predispositions
Authors: Soroosh Soosan , Soroush Mohsen G 
Published: November 2024

Background: Reactive arthritis (ReA) is generally defined by the presence of sterile synovitis and spondyloarthritis, which are clinically linked to symptoms such as inflammatory back pain, additive or migratory oligoarthritis, and various extra-articular manifestations. These symptoms typically emerge following a gastrointestinal or urogenital infection, usually within 1 to 3 to 6 weeks after the initial infection. Recent discoveries of microbial components within the joints of ReA patients suggest a reevaluation of this traditional definition is warranted. This study aims to identify trigger factors along with genetic or environmental predispositions that may render young men susceptible to spondyloarthropathies.
Methods: In 2003, a prospective evaluation was conducted involving 99 young patients referred to a rheumatology clinic. A thorough data collection process was implemented, encompassing general and clinical information, complete blood counts, viral serology, urine and stool analyses, HLA class I typing, and PCR analysis of synovial fluid.
Inclusion Criteria: There are no established diagnostic criteria for ReA; diagnosis is primarily clinical. For the patients in this study, Braun’s classification criteria were employed. Supporting investigations included elevated acute phase reactants (ESR, CRP), positive HLA-B27, and the detection of microbial DNA in synovial fluid via PCR.
Exclusion Criteria: Individuals with a history of other rheumatic diseases, ongoing antibiotic therapy, significant comorbidities that may complicate the diagnosis, recent immunosuppressive treatment, or any other causes of acute arthritis were excluded.
Results: The mean age of the patients was 21 years, with a standard deviation of 2.5 years. A seasonal variation was observed, with 35% of cases occurring in the summer. The mean latency period for the onset of arthritis was 31 days, with a standard deviation of 7 days. Prior sexual contact was reported by 27.3% of the patients. Common triggers included diarrhea (35.9%) and urethritis (22.3%), while 38.4% of patients reported no identifiable trigger.
Clinical manifestations primarily involved monoarthritis and oligoarthritis, predominantly affecting the lower extremities, as well as enthesitis in 33.3% of cases and eye involvement in 45%. Elevated levels of ESR (33.7 ± 4) and CRP (27.7 ± 4) were noted. HLA-B27 was found to be positive in 26% of patients, with HLA-B2701 and HLA-B2702 detected in 14% and 12% of cases, respectively. Other HLA types identified included HLA-B51 (13%), A24 (31%), A26 (11%), and Cw2 (29.3%).
Synovial fluid PCR tests identified Mycoplasma pneumonia in 3% of the cases and Chlamydia trachomatis in 5.1%. Other etiological agents included Brucella, Salmonella typhi, Salmonella paratyphi B, Salmonella enteritidis, Yersinia pseudotuberculosis, gonorrhea, and HIV.
Conclusion: Diagnosing Reactive Arthritis (ReA) is challenging because there is no definitive test available. The diagnosis depends on the clinical presentation, identification of triggering factors, and genetic background. This study highlights the differences in infection prevalence and HLA subtypes among various populations, emphasizing the necessity for customized diagnostic approaches.