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.

C. trachomatisis thought to be responsible for up to 10% of all cases of early inflammatory arthritis (seeChapter 370). Arthritis will develop in as many as 1 to 3% of patients with chlamydial urethritis. The incidence ofChlamydia-induced arthritis has been estimated to be 5 cases per 100,000 per year. The diagnosis is suggested by the presence of persistent arthritis in at least one joint, symptoms of genitourinary infection, detection of IgG or IgA anti-Chlamydiaantibodies, orChlamydiafound in genitourinary swabs or urine culture. Alternatively, chlamydial infection can be documented by enzyme immunoassay, direct fluorescent antibody testing or by using a DNA probe for chlamydial RNA. More than half of patients with Reiter's syndrome, non-gonococcal arthritis, or sexually acquired reactive arthritis will have antibodies toC. trachomatis,although positive cultures are seldom observed in patients with active disease.

The manifestations ofChlamydia-related reactive arthritis are similar to those described for classic Reiter's syndrome. However, only 20% of patients meet criteria for the diagnosis of Reiter's syndrome. Up to 15% of patients, especially women, have no urogenital manifestations at all. A chronic arthropathy develops in more than half, with nearly one third having inflammatory low back pain, enthesitis, or radiographic sacroiliitis. Fewer than 50% of patients are HLA-B27+.Chlamydia-induced arthritis apparently responds to antibiotic therapy, which is indicated in culture, serologic (IgM or IgA), or polymerase chain reaction-positive patients. A prolonged course (i.e., 12 weeks) of doxycyline, minocycline, or lymecycline may improve the symptoms.