Septic arthritis in patients with systemic lupus erythematosus: salmonella and nonsalmonella infections compared

OBJECTIVES: To assess the clinical characteristics and outcome of systemic lupus erythematosus (SLE) with septic arthritis. METHODS: In this 20-year retrospective study, we reviewed the charts of SLE patients with septic arthritis confirmed by synovial fluid analysis and culture. To identify risk factors for septic arthritis, data of SLE patients with septic arthritis were compared with data of 100 hospitalized SLE patients without septic arthritis. RESULTS: There were 10,732 inpatient records of 3,127 SLE patients; 29 SLE patients had septic arthritis. Their ages ranged from 14 to 68 years (mean, 35.1 +/- 14.1 years). The mean SLE duration before septic arthritis onset was 30.6 months. All patients received corticosteroids; 93% had active disease (SLEDAI > or = 4). Compared with controls, avascular necrosis (AVN) of the femoral head was the most common predisposing articular disease (Odds ratio, 3.799;CI, 1.59 to 9.05). Of the 29 patients, 17 (59%) had salmonella infections and 12 (41%) had other infections. Salmonella-infected patients were younger (28.7 +/- 10.4 years) than those with nonsalmonella infections (44.1 +/- 14.0 years; P = 0.002). The hip was the most commonly affected joint, especially in the salmonella group, followed by the knees and ankles. Salmonella-infected patients were more prone to oligo-articular septic arthritis. The overall mortality rate was 10%. CONCLUSIONS: Salmonella enteritidis B is the most common pathogen causing septic arthritis in younger SLE patients. Septic arthritis tended to be oligo-articular and involve the hip joint. AVN of the femoral head was the most common predisposing articular disease. Once septic arthritis is suspected, culture specimens should be collected and appropriate antibiotics given immediately.