La pyomyosite, au-delà des tropiques

Pyomyositis, a bacterial infection of one or more skeletal muscles of the trunk, limbs, or pelvis, is most often caused by Staphylococcus aureus, apparently expressing the Panton and Valentine leukocidin toxin. Initially described as a tropical disease, it can occur in all climates, with a clear increase in its incidence, both in children and adults. It progresses in three anatomical stages leading to an abscessed collection. Risk factors exist but are inconsistent. It may be complicated by septic emboli depending on the delay in diagnosis and therefore management or the frailty of the patient. The presence of septic arthritis in the vicinity leads to discussion of the origin of the infection, primary versus secondary pyomyositis. Effective imaging includes ultrasound of the painful area, CT-scan and especially MRI. The microroganism is identified quite rarely on blood cultures, possibly on puncture under ultrasound or CT-scan of the infected muscle. Other bacteria than Staphylococcus aureus can be responsible. Sometimes pyomyositis is multi-bacterial. A PCR research by 16S ribosomal RNA in the muscle sampling material is proposed. Single muscle involvement with inflammatory syndrome also leads to discussion of focal myositis or muscle infarction. Pyomyositis implies systematic antibiotic therapy given for a period of three to four weeks, focused initially on Staphylococcus aureus, but sometimes also on a negative bacillus in the case of immunosuppression, and adapted subsequently according to bacteriological results/evolution. An abscessed fluid collection can be drained under ultrasound or CT-scan, and sometimes if necessary in the operating room.