Tropical pyomyositis and necrotizing fasciitis.

Pyomyositis is a purulent infection of skeletal muscle that arises from hematogenous spread, usually with abscess formation. Necrotizing fasciitis is a more severe, rapidly progressive infection involving the superficial and deep fascia with necrosis and fluid collections that can be life threatening if left untreated. Both conditions may coexist, and concomitant cellulitis is often seen. A high incidence of these diseases occurs in the tropics, but they are increasingly being seen in temperate countries, due in part to their association with immunodeficiency conditions such as human immunodeficiency virus (HIV) infection, diabetes mellitus, and organ transplantation. This article aims to familiarize physicians with these entities, review their clinical manifestations and imaging features, and highlight the role of imaging in the management of patients with these conditions.