[Infectious osteoarthritis due to Propionibacterium acnes. Two new cases]

Propionibacterium acnes is an anaerobic germ, usually found as a saprophyte of the skin and the mucosa. It may be responsible for iatrogenic or spontaneous osteoarhritis.We report two new cases of septic arthritis induced by P. acnes: a case of iatrogenic spondylodiscitis and a case of spontaneous septic arthritis of the lumbar facet joints. The two patients were immunocompetent, without acne.Except for patients with criteria of the SAPHO syndrome (synovitis-acne-pustulosis-hyperostosis-osteomyelitis), osteoarthritis caused by P. acnes is increasingly described. The number of these infections is probably underestimated because of the technical problems involved in isolating P. acnes in the laboratory.