Rheumatoid arthritis is the major risk factor for septic arthritis in rheumatological settings

Septic arthritis (SA) is a clinical emergency with considerable morbidity and mortality that can lead to rapid joint destruction and irreversible functional loss. The reported incidence varies from 2-5 cases/100,000 person-years in the general population to 70 cases/100.000 person-years among patients with rheumatoid arthritis. In fact, individuals with rheumatoid arthritis are at particular risk for developing SA. This may be due to several reasons: joint disease predisposes to bacterial joint colonization and RA itself and its treatment with corticosteroids, disease-modifying antirheumatic drugs (DMARDs) and biological therapies may decrease the immune function required for protection from pathogens. Steroids and DMARDs seem to affect the leukocyte synovial count; indeed, RA patients with SA have a leukocyte count in synovial fluid (SF) lower than patients with SA without underlying rheumatic diseases. The diagnosis of SA in RA patients can be difficult because the development of a hot painful joint is often confused with a relapse of the underlying joint disease leading to delay in diagnosis. For this reason the microscopic analysis and culture of synovial fluid are crucial to exclude septic arthritis. (C) 2008 Elsevier B.V. All rights reserved.