Osteomyelitis in patients with systemic lupus erythematosus

OBJECTIVE: To investigate the clinical profile of and the risk factors for osteomyelitis in patients with systemic lupus erythematosus (SLE). METHODS: We reviewed 11 consecutive cases of patients with SLE who had also had osteomyelitis between 1981 and 2001 at a medical center in Taiwan, with special attention to predisposing factors, clinical features, laboratory values, and outcomes. RESULTS: The mean age at diagnosis of osteomyelitis was 34.5 +/- 22.0 years and the ratio of females to males was 9:2. The typical initial manifestations were nonspecific focal pain (82%) and fever (64%). The most commonly affected sites were the long bones (6 cases, 54%), followed by the vertebrae (4 cases, 36%). Salmonella (5 cases, 45%) and Staphylococcus aureus (4 cases, 36%) were the major causative organisms. Interestingly, once long bones had become involved, 5 of 6 (83%) isolates proved to be Salmonella, and for vertebral osteomyelitis, 3 of 4 (75%) isolates proved to be S. aureus. Predisposing factors include an active status of SLE (SLEDAI score >/= 4, 100%), coexistent underlying systemic disease (91%), chronic renal disease (82%), and intensified immunosuppressive agent usage (82%). Laboratory values either reflected an acute phase reaction that would be expected in an infection, such as a raised C-reactive protein (100%) and neutrophilia (55%), or reflected features consistent with active lupus disease. Four patients had longterm motor deficits and another patient died. Poor prognostic factors include delayed diagnosis, vertebral involvement, artificial implants in bones, and chronic carrier status. CONCLUSION: In patients with SLE who present with local osteoarticular pain, particularly those whose disease is active and who also have chronic renal disease and were taking intensified immunosuppressive agents, osteomyelitis must be considered seriously. Salmonella should be considered as a potential contributing pathogen for long bone osteomyelitis and S. aureus should be considered for cases of vertebral osteomyelitis when conducting empirical antimicrobial therapy. Early recognition and treatment is essential to avoid longterm sequelae or death.