Nontropical pyomyositis in an immunocompetent host.

Pyomyositis is a primary infection of the striated muscle. We describe the clinical and imaging features of 2 cases with nontropical pyomyositis in immunocompetent hosts. Staphylococcus aureus was the causative agent; the treatment included antibiotics and either computed tomography or magnetic resonance-guided percutaneous needle drainage, avoiding open drainage. This treatment modality was successful with complete recovery of movement. Because of the rarity of pyomyositis in temperate climates, the common lack of specific signs or symptoms, and the frequent negative blood cultures, considerable delay precedes the diagnosis. Fever, elevated erythrocyte sedimentation rate, and muscle stiffness are diagnostic clues. Increased awareness, especially in immunocompetent hosts, should lead to earlier diagnosis and treatment with improved outcomes. Diagnosis and treatment can be reached at the same time in some cases by image-guided percutaneous drainage.