A retrospective study of joint infections in patients with systemic lupus erythematosus.

The aim of this study was to analyze the clinical characteristics of systemic lupus erythematosus (SLE) patients with joint infections. We retrospectively reviewed the medical records of 11,734 SLE patients admitted to Peking Union Medical College Hospital (PUMCH) from January 1990 to December 2016. Twenty patients who developed joint infections were identified. Subjects without joint infections (designated as control patients) were selected from the pool of SLE patients using a 1:4 systematic sampling method. The median disease duration from SLE onset to joint infection was 23 months (range 4 to 156 months). The symptoms of patients with joint infections manifested as joint pain (all cases), swelling (14 cases), and fever (15 cases). All patients had oligo-arthritis, and the knee was the joint most commonly affected joint. There were 7 patients in the Salmonella group and 5 in the Staphylococcus aureus group. One patient was infected with Streptococcus, and 7 patients were infected with Mycobacterium. SLE patients with and without joint infections demonstrated significant differences (P < 0.05) regarding the following symptoms: pre-existing arthritis (65.0 vs 33.8%), gastrointestinal involvement (5.0 vs 26.3%), cardiac damage (5.0 vs 31.3%), elevated C-reactive protein (CRP) (80.0 vs 22.5%), and elevated SLE Disease Activity Index (SLEDAI) score (≥5) (30.0 vs 77.5%). When an SLE patient presents with pre-existing arthritis and suddenly develops asymmetric oligo- or large-joint swelling and pain with elevated CRP levels and low disease activity, joint infections should be considered. Early treatment could protect the joint and improve functional outcomes.