Diagnosis and classification of reactive arthritis.

Reactive arthritis is a form of seronegative spondyloarthritis clinically associated with inflammatory back pain, additive or migratory oligoarthritis, and extra-articular symptoms that typically follow a gastrointestinal or urogenital infection by a minimum of 1 to a maximum of 3-6 weeks. Once arthritis is observed, however, microbial tests and blood or synovial fluid cultures are negative, and only serum antibodies are detected. Reactive arthritis commonly affects young adults, most frequently white and carrying the HLA-B27 allele. The genetic susceptibility appears as necessary with only 1-15% of cases of infection developing reactive arthritis. Clinical symptoms are different from septic arthritis which manifests with fever, systemic signs of infection, and monoarthritis. The presence of large joint oligoarthritis, urogenital tract infection, and uveitis characterizes Reiter's syndrome as a clinical subtype. Ocular, skin, and heart involvement are not uncommon and may be largely variable in severity. Diagnostic criteria are based on the ACR guidelines and include rheumatological signs along with a proof of infection.