Reactive Arthritis Save
Prof Robert Inman gave a great summary of the state of the art in reactive arthritis (ReA).
He highlighted the nature experiments that have occurred when large groups of people get simultaneous food poisoning. An informative case in Canada of Salmonella GI infection 6.4% (n=27) of a large group of 423 police officers who developed reactive Salmonella infections developed ReA. Subsequently 18 (4.3% of the total) developed chronic ReA. (Reference - Thomson et al American Journal of Medicine, 1995;98:13). Studies like this suggest extra-articular features like ocular inflammation occurs in 20% of ReA and oral ulcers also in 12%.
Genetic studies of a Toll like receptor-2 SNP associated with propensity to reactive arthritis. This suggests that genetic differences in innate immunity impact on the risk of developing reactive arthritis.
Samonella, Champhylobactor, Shigella and Yersinia are the common causes of reactive arthritis. The frequency of development is 1-9% of those who are infected via the GI route. Sexually contracted reactive arthritis has a frequency of 1-4%. The common organisms are Chlamydia and Neisseria.
The challenge with drawing good conclusions from the literature is the lack of a consistent definition of ReA. One known factor is that HLA-B27 is a strong predictor of chronicity of reactive arthritis.
Investigations: Need to exclude septic arthritis, and think about alternative diagnoses like gout and rheumatoid arthritis. A Chlamydia nucleic acid amplication test from the urine is of value.
Treatment: First line treatments are NSAIDs and intra-articular steroid injections. Second line treatment includes oral glucocorticoids, sulphasalazine and methotrexate. Based on limited published work TNF inhibitors seem to be safe for the treatment of ReA.
Can we use antibiotics to treat ReA? Trials of antibiotics to treat GI-induced ReA have been largely unsuccessful. However a recent randomised trial from John Carter in Chlamydia ReA showed positive results (Arthritis Rheum 2010;62:1298). Using combination doxycycline and azithromycin for 6 months and matched placebo in 42 subjects demonstrated the antibiotics reduced tender and swollen joint count. No clinical worsening of disease after cessation of antibiotics at 6 months.
This response raised a serious question about what reactive arthritis is. The results suggest that reactive arthritis sits in an intermediate space between septic arthritis and spondyloarthritis because of its response to antibiotics. Time will tell…