[Arthritis and infections]

Arthritis caused by infectious agents can be secondary to direct invasion of the joint space or to immune mechanisms (subsequent to or concomitant to an infection). Septic arthritis refers to a situation when bacteria can be cultured in synovial fluid. Arthritis can complicate for example meningococcemia or infection by Neisseria gonorrhoeae or Haemophilus influenzae. Reactive (postinfectious) arthritides are an important diagnostic category within a pediatric rheumatology practice. Yersinia and, less frequently, Salmonella, play an important role in postdiarrheal disorders. The arthritis that can ensue is usually oligoarticular and occurs 1-2 weeks after the enteric infection. Reiter's syndrome, rare in the pediatric age, is characterized by the triad urethritis-conjunctivitis-arthritis. Postviral arthritides can occur after a variety of viral infections, including Parvovirus B19, rubella, and others (e.g. hepatitis B, Epstein-Barr virus, chickenpox, mumps). Especially in patients with acute arthritis, the presence of preceding infections should always be investigated. Although the majority of postinfectious arthritides are self-limiting in nature and do not require specific treatment, conditions such as Lyme borreliosis and rheumatic fever can be associated with significant morbidity, and sometimes can be even lethal.