Prevalence and characteristics of concomitant septic and crystal-induced arthritis: A hospital database and literature review.

Background and objectives: Concomitant septic and crystal-induced arthritis is a rare condition. Failure to diagnose this condition can result in significant harm to the patient. This study aims to investigate the prevalence and characteristics of concomitant septic and crystal-induced arthritis.

Methods: A retrospective study included patients diagnosed with concomitant septic and crystal-induced arthritis confirmed by positive bacterial culture and intracellular crystals in synovial fluid of the same joint, from January 1, 2015, to July 31 ,2024.

Results: A total of 45 cases were defined as having the prevalence of concomitant septic and crystal-induced arthritis among patients with crystal-induced arthritis of 4% (45/1116). Demographic characteristics showed male predominance (73.3%) with a mean ± SD age of 62.8 ± 14.4 years. Acute monoarthritis (66.7%, n = 30), which primarily affected the knee (68.9%, n = 31), was the most common presentation. Fever was present in 95.6% of cases. The median synovial white blood cell (WBC) count was 61, 478 cells/μL (interquartile range: 33, 600-131, 030). The mean ± SD C-reactive protein (CRP) level was 215 ± 96.7 mg/L. Monosodium urate crystals were found in 80% (n = 36) of the cases. The predominant bacteria were Staphylococcus (48.9%, n = 22), with Methicillin-sensitive Staphylococcus aureus (MSSA) being the most common (28.9%, n = 13), followed by Streptococcus dysgalactiae (15.6%, n = 7) and gram-negative bacilli (15.6%, n = 7). The mortality rate was 15.6% (n = 7).

Conclusion: The prevalence of concomitant septic and crystal-induced arthritis was 4% among patients with crystal-induced arthritis, especially among those with acute fever and high synovial WBC counts. The chance of concomitant septic and crystal-induced arthritis is very low in cases with synovial WBC < 12,000 cells/μL.