Reactive arthritis: a comprehensive journey through diagnostic findings

Reactive arthritis, initially described at the beginning of the twentieth century, is characterized by a sterile articular inflammation occurring several days to weeks after a bacterial gastrointestinal or urogenital infection. The most common agents include Chlamydia trachomatis, Ureaplasma urealyticum, and Neisseria gonorrhea for the venereal type and Salmonella enteriditis, Shigella flexneri, Yersinia enterocolitica for the post-enteric type. The prevalence of reactive arthritis varies geographically but overall, worldwide, it is estimated as 1/1000 persons. It is more common in young adults (18 to 40 years old) and in terms of gender, there is not a significant difference between men and women for post-enteric infections while the risk of the endemic type is higher in men with a ratio of 9:1. Guidelines and diagnostic algorithms taking into account the identification of the etiological agent and the timing of infection have been proposed in the literature. Typically, it is an asymmetric mono- or oligo-arthritis with a predilection for the lower extremities falling under the spondyloarthritis umbrella having shared clinical features. At imaging, enthesitis is considered a hallmark of the disease although other typical signs of inflammatory joint disease such as synovitis, periostitis, and erosions can be detected taking advantage of the various radiological and hybrid techniques according to the affected areas.