Reactive arthritis

In medicine, reactive arthritis is an "aseptic, inflammatory arthritis developing secondary to a primary extra-articular infection, most typically of the gastrointestinal tract or urogenital system. The initiating trigger pathogens are usually shigella; salmonella; yersinia; campylobacter; or chlamydia trachomatis. Reactive arthritis is strongly associated with HLA-B27 antigen."

Epidemiology
The frequency of reactive arthritis after an infection is estimated to be 0.6 to 3.1 cases/100,000.