Pyomyositis 2016: a challenging diagnosis

Key words: Pyomyositis, Muscle infection, Diagnosis, Treatment, Staphylococcus aureus

Pyomyositis is a subacute, deep bacterial infection of skeletal muscles. Originally described in tropical areas, mainly in malnourished and immunocompromised subjects (“tropical pyomyositis”), it has been subsequently reported with an increasing frequency also in temperate climates. Larger muscle groups located in the pelvic girdle and in the lower extremities (including the thigh, calf and gluteal muscles) are most commonly affected, but any muscle group can be involved. S. aureus is the most common causative agent, being responsible for up to 90% of tropical cases and up to 75% of cases in temperate areas. Local trauma as a predisposing factor is reported in up to 39% of cases. There are no specific laboratory tests for pyomyositis. MRI is the gold standard for the diagnosis. Treatment of pyomyositis largely depends on the stage of the disease. Prompt intravenous antibiotic therapy targeted on Staphylococcus aureus is generally effective for early infections. Both antibiotic therapy and drainage are necessary in more advanced stages. The paper reports one of muscle gluteus maximus involvement, reviews the literature and describes the experience with pyomyositis at Institute for Maternal and Child Health IRCCS “Burlo Garofolo” (Trieste, Italy) over the past ten years.