[Septic arthritis: a 12 years retrospective study in a rheumatological university clinic]

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.

Staphylococcus aureus bacteremia with iliac artery endarteritis in a patient receiving ustekinumab

BACKGROUND

Ustekinumab (Stelara®), a human monoclonal antibody targeting the p40-subunit of interleukin (IL)-12 and IL-23, is indicated for moderate to severe plaque psoriasis and psoriatic arthritis. In large multicenter, prospective trials assessing efficacy and safety of ustekinumab increased rates of severe infections have not been observed so far.

CASE PRESENTATION

Here, we report the case of a 64-year old woman presenting with chills, pain and swelling of her right foot with dark maculae at the sole, and elevated inflammatory markers. She had received a third dose of ustekinumab due to psoriatic arthritis three days before admission. Blood cultures revealed growth of Staphylococcus aureus and imaging showed a thickening of the aortic wall ventral the bifurcation above the right internal iliac artery, resembling an acute bacterial endarteritis. Without the evidence of aneurysms and in absence of foreign bodies, the decision for conservative management was made. The patient received four weeks of antibiotic therapy with intravenous flucloxacillin, followed by an oral regime with levofloxacin and rifampicin for an additional four weeks. Inflammatory markers resolved promptly and the patient was discharged in good health.

CONCLUSION

To our knowledge, this is the first report of a severe S. aureus infection in a patient receiving ustekinumab. Albeit ustekinumab is generally regarded as a safe drug, severe bacterial infections should always be included in the differential diagnosis of elevated inflammatory markers in patients receiving biologicals as these might present with nonspecific symptoms and fever might be absent. Any effort to detect deep-seated or metastatic infections should be made to prevent complications and to secure appropriate treatment. Although other risk factors for an invasive staphylococcal infection like psoriasis, recent corticosteroid injection, or prior hospitalisations were present, and therefore a directive causative link between the S. aureus bacteraemia and ustekinumab can not be drawn, we considered the reporting of this case worthwhile to alert clinicians as we believe that ongoing pharmacovigilance to detect increased risks for rare but severe infections beyond phase II and phase III trials in patients treated with biologicals is essential.

Procalcitonin levels in fresh serum and fresh synovial fluid for the differential diagnosis of knee septic arthritis from rheumatoid arthritis, osteoarthritis and gouty arthritis

Whether the levels of procalcitonin (PCT) in the serum and synovial fluid are effective indicators for distinguishing septic arthritis (SA) from non-infectious arthritis remains controversial. The present study aimed to evaluate whether PCT levels in fresh serum or fresh joint fluid may be used in the differential diagnosis of SA from rheumatoid arthritis (RA), osteoarthritis (OA) and gouty arthritis (GA). From January 2012 to June 2013, 23 patients with knee SA, 21 patients with RA, 40 patients with OA and 11 patients with GA were enrolled in the current study. The levels of PCT were measured within 24 h after specimen collection at room temperature. An enzyme-linked fluorescence assay (ELFA) was used to detect the levels of PCT in the serum and synovial fluid. The correlations between the levels of PCT in the serum and synovial fluid and the arthritic patient groups were determined by the Nemenyi test. Areas under the receiver operating characteristic (ROC) curve were calculated to evaluate the accuracy of the correlations. The levels of PCT in the serum and joint fluid of the patients in the SA group were higher compared with those of the other groups (P<0.01) and there were no significant differences among the RA, OA and GA groups in these levels. A PCT level of <0.5 μg/l in the serum and synovial fluid had high specificity in the differential diagnosis of SA from RA, OA and GA. Synovial fluid PCT revealed significantly greater sensitivity than serum PCT. The accuracy of the differential diagnosis of SA by the serum levels of PCT was significantly lower than that by the synovial fluid levels of PCT. The levels of PCT in the serum and synovial fluid may be used as alternative laboratory indicators to distinguish between SA and the non-infectious types of arthritis; however, the PCT levels in fresh synovial fluid are more sensitive and accurate indicators than PCT levels in fresh serum.