Bacterial infections that cause acute suppurative arthritis usually enter the joints from distant sites by hematogenous spread. In neonates, however, contiguous spread from underlying epiphyseal osteomyelitis may occur. H. influenza arthritis predominates in children younger than 2 years of age, S. aureus is the main agent in older children and adults, and gonococcus is prevalent during late adolescence and young adulthood. Individuals with sickle cell disease are prone to infection with Salmonella. These joint infections affect the sexes equally except for gonococcal arthritis, which is seen mainly in sexually active women. Individuals with deficiencies of complement components (C5, C6, C7, or C9) are susceptible to disseminated gonococcal infections and hence arthritis.
The classic presentation is the sudden development of an acutely painful, warm, and swollen joint that has a restricted range of motion. Systemic findings of fever, leukocytosis, and elevated sedimentation rate are common. In 90% of nongonococcal cases, the infection involves only a single joint, most commonly the knee, followed in decreasing frequency by the hip, shoulder, elbow, wrist, and sternoclavicular joints. The axial joints are more often involved in drug users. Joint aspiration is diagnostic if it yields purulent fluid in which the causative agent can be identified. As mentioned earlier, cartilage has limited repair potential, so prompt recognition and effective anti-microbial therapy is vital to prevent permanent joint destruction.
Lyme arthritis is the leading arthropod-borne disease in the United States, predominantly affecting New England and mid-Atlantic states, but the geographic range and incidence are increasing. It is caused by infection with the spirochete Borrelia burgdorferi, which is transmitted by deer ticks of the Ixodes ricinus complex. In its classic form, Lyme disease progressively involves multiple organ systems through three clinical phases (
Fig. 21.40 ). The initial infection of the skin, or early localized stage, is followed by an http://ebooksmedicine.net
Fig.21.40Lymediseaseprogressesthroughthreeclinicallyrecognizablephases:earlylocalized,earlydisseminated,andlatepersistent.Althoughinitialmanifestationsresultdirectlyfromspirocheteinfection,latersignsandsymptomsarelikelyimmune-mediated.(Figure modified from Dr. Charles Chiu, University of California San Francisco, San Francisco, California. Used with permission.) early disseminated stage involving skin, cranial nerves, heart, and meninges. If left untreated, arthritis, especially of the knee, occurs weeks to months after infection.
Currently, arthritis occurs in less than 10% of cases because most patients are cured at an earlier stage. However, if left untreated approximately 60% to 80% of individuals develop a migratory arthritis (Lyme arthritis) lasting for weeks to months. Spirochetes can only be identified in about 25% of joints with arthritis, but the diagnosis can be confirmed by serologic testing for anti-Borrelia antibodies. Treatment of Lyme disease consists of antibiotics with activity against Borrelia. Cure rates of 90% have been achieved with standard regimens. A vaccine is under development. However, a chronic arthritis that is antibiotic refractory can develop in the late disseminated stage. In many of these patients, Borrelia cannot be detected in the joint fluid even by PCR. It has been proposed that cellular (especially TH1) and humoral responses to Borrelia outer surface protein A may initiate this late, autoimmune, arthritis. The chronic manifestations, in addition to joint pain, can include nonspecific symptoms (fatigue, cognitive complaints), known collectively as posttreatment Lyme disease syndrome (PTLDS).