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Primary (tropical) pyomyositis 

Primary (tropical) pyomyositis

Primary (tropical) pyomyositis

D A Warrell



New information on pathogenesis and imaging.

Updated on 28 Nov 2012. The previous version of this content can be found here.
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date: 29 April 2017

Pyomyositis is a primary intramuscular abscess, not tracking from adjacent structures but usually presumed to be haematogenous in origin. Formerly a disease almost exclusively of tropical developing countries, it is now seen increasingly in patients in Western countries who have underlying diseases and immunosuppression, notably HIV infection.

Aetiology—transient bacteraemia may seed an abscess in a focal area of previously damaged muscle if there is immunocompromise. The predisposing vulnerability of apparently healthy younger people in the tropics is unexplained, but malnutrition and preceding arboviral or helminthic infections are postulated. Staphylococcus aureus accounts for 90% of tropical and 70% of nontropical cases.

Clinical features, investigation and treatment—pyomyositis may evolve through subacute, suppurative, and septicaemic phases over weeks or months. Early clinical evidence is local swelling and tenderness in a muscle, often with minimal systemic signs. Diagnosis is confirmed by imaging, ideally gadolinium-enhanced MRI. Treatment requires (1) drainage by open surgery or image-guided needle aspiration—whenever there is suppuration; (2) antibiotics—initial regimen must cover S. aureus, but should then be guided by culture findings.

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