De novo Propionibacterium acnes septic arthritis.

We report the third identifiable case of septic arthritis due to Propionibacterium acnes arising in the absence of prior surgical intervention. This anaerobic Gram-positive bacillus is now recognised as an important cause of postoperative infections, typically presenting in an indolent fashion some months after surgery. Reports of de novo septic arthritis due to P. acnes are exceedingly rare. Our case adds to the literature and significantly broadens the reported pathogenic potential of the organism, which in this instance has caused rapid and serious joint destruction.