Bacterial Pyomyositis

Bacterial pyomyositis has been defined as a subacute, deep bacterial infection of the soft tissues. The entity was originally described only in tropical climates, but it is increasing in incidence in temperate climates, such as in the United States. This is mainly attributed to the presence of immunocompromising states such as HIV/AIDS or liver disease. The etiology of pyomyositis remains a mystery, but its characteristics are well-described. If untreated, the disease process progresses through three distinct stages. The first stage is defined by vague complaints, muscle pain, and a low-grade fever. The second stage presents as worsening pain, swelling, fever, and actual abscess formation in the muscle. If the patient remains untreated, pyomyositis progresses to the third stage, which includes septicemia and possible septic shock. Large muscles around the pelvis are most commonly affected, and Staphylococcus aureus is the bacteria seen in most documented cases. To make a timely diagnosis and prevent serious sequelae, physical examination, laboratory results, imaging studies, and a high clinical suspicion must all be combined. Magnetic resonance imaging is the diagnostic study of choice, but it may be inconclusive early in the disease process. Definitive diagnosis must be made with aspiration or surgical drainage. Once diagnosed, treatment consists of appropriate intravenous antibiotics and possible surgical intervention. A full recovery is expected if appropriate treatment is initiated early in the process.