ESSENTIALS OF DIAGNOSIS
Oligoarthritis, conjunctivitis, urethritis, keratoderma blennorrhagicum, and mouth ulcers.
Usually follows dysentery or a sexually transmitted infection.
HLA-B27–positive in 50–80% of patients.
Reactive arthritis is precipitated by antecedent GI or genitourinary infections. and manifests as an asymmetric sterile oligoarthritis, typically of the lower extremities. It is frequently associated with enthesitis. Extra-articular manifestations are common and include urethritis, conjunctivitis, uveitis (eFigure 20–38), keratoderma blennorrhagicum, and mucocutaneous lesions. Reactive arthritis occurs most commonly in young men and is associated with HLA-B27 in 80% of White patients and 50–60% of Black patients.
Acute iridocyclitis with hypopyon in a patient with reactive arthritis. (Reproduced, with permission, from Vaughan DG, Asbury T, Riordan-Eva P [editors]. General Ophthalmology, 15th ed. Originally published by Appleton & Lange. Copyright © 1999 by The McGraw-Hill Companies, Inc.)
Most cases of reactive arthritis develop within 1–4 weeks after either a GI infection (usually with Shigella, Salmonella, Yersinia, or Campylobacter) or a sexually transmitted infection (with Chlamydia trachomatis or perhaps Ureaplasma urealyticum). Whether the inciting infection is sexually transmitted or dysenteric does not affect the subsequent manifestations but does influence the gender ratio. The spectrum of pathogens known to cause reactive arthritis is broadening to include Mycobacterium, Staphylococcus, and SARS-CoV-2. Synovial fluid from affected joints is culture-negative. A clinically indistinguishable syndrome can occur without an apparent antecedent infection, suggesting that subclinical infection can precipitate reactive arthritis or that there are other, as yet unrecognized, triggers. Although affected joints are sterile, molecular techniques provide evidence that antigens from putative inciting organisms (and DNA in the case of Chlamydia) are present in synovial tissue, even years after the clinical disease. The pathogenic significance of these findings remains unclear.
The arthritis is most commonly asymmetric and frequently involves the large weight-bearing joints (knee and ankle); sacroiliitis or ankylosing spondylitis is observed in at least 20% of patients, especially after frequent recurrences. Systemic symptoms including fever and weight loss are common at the onset of disease. The mucocutaneous lesions may include balanitis (Figure 20–9), stomatitis, and keratoderma blennorrhagicum (eFigure 20–39), indistinguishable from pustular psoriasis. Involvement of the fingernails in reactive arthritis mimics psoriatic changes. When present, conjunctivitis is mild and occurs early in the disease course. Anterior uveitis, which can develop at any time in HLA-B27–positive patients, is a more clinically significant ocular complication. Carditis and aortic regurgitation may occur. While most signs of the disease disappear within days or weeks, the arthritis may persist for several months or become chronic. Recurrences involving any combination of the clinical manifestations are common and are sometimes followed by permanent sequelae, especially in the joints (eg, articular destruction).