Multifocal pyomyositis. Diagnosis on technetium-99m MDP bone scan.

Pyomyositis is a bacterial infection of skeletal muscle occurring in the absence of trauma or a primary site of infection. The condition is rare in temperate climates. The diagnosis is often difficult to make and frequently delayed since the suppurative process is confined by the tense overlying muscle and fascia. The bone scan is very useful in differentiating underlying osteomyelitis and septic arthritis. An 11-year-old boy is described who presented with multifocal pyomyositis in the elbow region and thigh. Lateral blood pool images suggested infection with liquefaction within the muscles without evidence of osteomyelitis.