REACTIVE ARTHROPATHIES.

"Reactive arthritis" refers to the occurrence of an acute, non-suppurative, sterile inflammatory arthropathy arising after an infectious process but at a site remote from the primary infection. Reiter's syndrome is one of the most common examples of reactive arthritis. The microbial pathogens commonly associated with reactive arthritis areShigella, Salmonella, Yersinia, Campylobacter,andChlamydia.The reactive nature of these arthritides has been debated, inasmuch asChlamydia, Yersinia,andSalmonellamicrobial antigens have been identified at sites of tissue inflammation, thus suggesting that an ongoing immune response to disseminated material, rather than a reactive condition, may be the pathogenic mechanism. Many reactive arthritides occur after a known infection and have therefore been termed "post-infectious." Although the pathologic processes appear to be similar, this distinction may be important with regard to potential responsiveness to antibiotic therapy.

Reactive arthritis begins as an asymmetrical oligoarthritis, often preceded by an identifiable infectious event by 1 to 4 weeks. The temporal sequence suggests that these reactive disorders are triggered by an antecedent infectious process. Many patients without an identifiable infectious trigger have a similar constellation of signs and symptoms. The findings of sterile inflammatory synovial effusions, lymphocytes at sites of tissue inflammation, responsiveness to anti-inflammatory and immunosuppressive regimens, and the association with HLA-B27 suggest a common immunopathogenesis. Extra-articular manifestations may be a prominent feature of the reactive arthropathies. Although frequently self-limiting, these disorders have the potential for chronicity and serious articular damage to the peripheral or axial joints.

SHIGELLA.

The occurrence of reactive arthritis after epidemics ofShigelladysentery has documented the arthritogenicity of this organism. Several reports suggest that Reiter's syndrome develops in 0.2 to 2% of infected individuals following epidemic shigellosis. Infections withShigella flexneritrigger Reiter's syndrome, whereas the more frequentShigella sonneidoes not. In most cases, the diarrheal illness resolves before the articular symptoms appear.

SALMONELLA.

Salmonella typhimuriumis the most commonSalmonellaspecies inducing reactive arthritis. A sterile arthropathy will develop in as many as 6 to 10% of infected individuals within 3 weeks of aSalmonellaoutbreak. Nearly 60% of patients will possess HLA-B27 or one of the cross-reactive antigens. (HLA-B7 or HLA-B60). No clinical differences betweenShigella- andSalmonella-induced reactive arthritis have been observed.

YERSINIA.

Yersinia enterocoliticais a common cause of reactive arthritis in epidemic areas such as Scandinavia but is rarely encountered inEnglandor theUnited States.Yersiniaarthritis most commonly affects young adults as an acute, self-limiting gastrointestinal illness that may have associated joint complaints in 50% of cases. Chronicity, severity, sacroiliitis, and ocular inflammation are more likely in HLA-B27+ individuals. The arthritis is predominantly oligoarticular, usually affects the lower extremities and hands, and may run a chronic or relapsing course. Chronic low back pain and sacroiliitis are seen in one third of patients, but severe spinal ankylosis is rare. Extra-articular features occur in 20 to 30% of individuals. Erythema nodosum and glomerulonephritis have been described in HLA-B27- individuals. Sustained elevations of IgA antibody titers correlate with persistent infection, chronic arthritis, and occult enteritis. Treatment is similar to that for other reactive arthropathies. However, appropriate antibiotic therapy should be used in patients with persistently positive stool cultures forYersinia.

CHLAMYDIA.