Polyarticular septic arthritis in an 11-year-old child.

A child with polyarthritis is always a diagnostic challenge for the treating physician. Polyarthritis can be a clinical manifestation of diverse disease processes, and the differential diagnosis is understandably very broad. We present a case of polyarticular septic arthritis, which is osteomyelitis complicated, caused by Streptococcus pyogenes identified by 16S polymerase chain reaction (PCR) in a healthy child, with previous synovial fluid cultures negative. This case underlines the importance of early aggressive therapy and the role of PCR/16S ribosomal bacterial DNA amplification to detect the causative microorganisms in septic arthritis when cultures remain negative.