[Tropical myositis]

Tropical pyomyositis (TP) is a microbial infection involving one or more skeletal muscles that rapidly leads to abscess. The most common infectious agent is Staphylococcus aureus. Since muscle tissue is highly resistant to infection, occurrence of TP is contingent upon one or more compromising factors such as trauma, skin lesions, parasitosis, or malnutrition. HIV infection is currently a major factor in the occurrence of TP. While Staphylococcus aureus accounts for 80% of cases, other microbial agents have been identified including gram-positive cocci and gram-negative bacilli. TP is endemic in intertropical zones of Africa and Latin America and in island areas of the Pacific Ocean. However a growing number of non-tropical cases have been reported in association with AIDS. The most frequent presentation is single-muscle involvement in the thighs, calves, and buttocks. The symptomatic phase or suppurative phase is almost always associated with hyperthermia. The infected muscle indurates prior to development of characteristic fluctuance. Hemocultures are seldom positive but needle aspiration may confirm diagnosis. Ultrasound imaging can allow early detection. Severe sepsis or cardiovascular, renal, or pleuropulmonary complications are observed in 10% of cases. Treatment is antibiotic therapy with penicillin M and surgical drainage or needle puncture of abscess cavities. Prognosis is generally favorable even in HIV-infected patients.