Unusual case of paediatric septic arthritis of the lumbar facet joints due to Kingella kingae.

A 32-month-old boy presented with febrile limping that had developed over 6days, associated with right lumbosacral inflammatory swelling. Magnetic resonance imaging (MRI) showed joint effusion of the right L5-S1 zygapophyseal joint, complicated by destructive osteomyelitis of the L5 articular process and paraspinal abscess. Surgery was decided to evacuate the fluid accumulation and rule out differential diagnoses. The diagnosis of septic arthritis of the facet joint was confirmed intraoperatively; real-time quantitative PCR analysis identified Kingella kingae. This is the first substantiated paediatric case of zygapophyseal joint septic arthritis due to K. kingae. K. kingae is the most common pathogen responsible for invasive osteoarticular infection in children under 4years of age. Since empiric antibiotics are effective in early stages, physicians should consider the possibility of spinal infections due to K. kingae when a limping child under 4years of age presents with a fever.