Reactive Arthritis

Reactive arthritis is a sterile inflammatory spondyloarthritis that develops after an infection elsewhere in the body. The organism is not assumed to be growing inside the joint. Instead, the immune response triggered by infection continues to inflame synovium and related tissues after the original infection has improved or resolved. The usual history is gastrointestinal or genitourinary infection followed by arthritis 1 to 6 weeks later. Recognized triggers include Chlamydia trachomatis, Salmonella, Shigella, Yersinia, and Campylobacter. SARS-CoV-2 is also recognized as a potential trigger. The joint pattern that should raise suspicion is asymmetric oligoarthritis: inflammation in a small number of joints, unevenly distributed rather than mirrored on both sides. A patient may describe one swollen knee and a painful ankle rather than the symmetric small-joint pattern more typical of rheumatoid arthritis. The preceding infection can be easy to miss. Diarrhea may have lasted only a few days, and genitourinary symptoms may be absent, mild, or already resolved when joint pain begins. The nurse who asks, “Any diarrhea, urinary symptoms, genital symptoms, or new sexual exposure in the past month or so?”...