University of Alabama at Birmingham

2002 Case #9

Universidad Peruana Cayetano Heredia
(Links to Other 2002 Cases are at bottom of this page)
The final week of the course each year takes place in Iquitos, located on the banks of the Amazon River, which is the largest city in the world (over 500,000 inhabitants) that is not reachable by road. The nearest road ends over 800 km away and all goods and people must come in by air or river. The following case was seen by participants on the Pediatric ward of the Hospital Apoyo de Iquitos.
Image for 03/29/02History: 8 year old with a history of Plasmodium falciparum approximately 1 month prior to admission which was treated with 7 days of oral quinine and clindamycin. The patient was afebrile for 1 week, and then 10 days prior to admission developed daily high spiking fevers, this time accompanied by significant muscle pain and tenderness localized to small areas of both calves and both deltoids.

Epidemiology: Resident of a small community in the jungle outside Iquitos. No ill contacts. No TB history or contact. No specific exposures. No animals in the house.

Physical Examination: Temperature 40.2°C. Normotensive, heart rate 96. Chest, cardiovascular, abdominal exams normal. No organomegaly or lymphadenopathy. Right deltoid and both calves all visibly swollen with focal areas of about 10 cm extremely painful to light palpation (see digital image). The affected areas felt firm without any redness, cellulitis, or warmth, and without any abnormalities in the consistency of the skin or subcutaneous tissue. No break in skin integrity noted anywhere distally on any limb.

Labs/X-ray: (on admission) Hematocrit 24%, WBC 9300, 44 segs, 2 bands, 36 lymphs, 8 eos. Chest and skeletal x-rays normal. Malaria smear negative. Blood cultures or sophisticated imaging are not available at this district hospital.



University of Alabama at Birmingham

2002 Case #9
Diagnosis and Discussion

Universidad Peruana Cayetano Heredia
(Links to Other 2002 Cases are at bottom of this page)
Diagnosis: Tropical Pyomyositis.
Image for 03/29/02 DiscussionDiscussion: Pyomyositis is a primary purulent infection of skeletal muscle that occurs without penetrating trauma or contiguous spread from adjacent tissue. Because this disease is common in the tropics and very rare in temperate climates, it is usually called tropical pyomyositis. While the diagnosis is apparent on clinical grounds to all with experience in the tropics. it may present a more difficult diagnostic dilemma to those without such experience. It is common throughout the tropics, but hot humid areas of Africa, Asia, and Latin America seem most affected. At the Iquitos Hospital at least one case per week is seen.

Our patient was taken to the OR where the affected areas were exposed down to deep muscle. In each case large pockets of characteristic chocolate-colored pus (see arrows in digital image of leg wound) were encountered and adjacent areas of necrotic muscle were debrided. Intravenous oxacillin was to be continued until complete defervescence and 2 weeks of therapy with oral dicloxacillin completed. The hospital has no microbiology facilities, but in Perú, as in other countries, >95% of pyomyositis is caused by staphylococcus (mostly) and streptococci when it has been investigated.

Pyomyositis remains a poorly understood disease and the primary cause remains elusive. Many authors have invoked preceding apparent or inapparent blunt trauma to the affected muscle area as a predisposing factor. The finding that up to 25% of patients have multiple abscesses (as with our patient) speaks against this. Bacteremia from an occult focus does not seem to have a role. When investigated, only 5% of patients have positive blood cultures, and all these patients have untreated disease of long duration. Similarly, purulent lesions in non-muscle tissues are extraordinarily uncommon even in those with long duration of disease or multiple skeletal abscesses. Modern molecular techniques have yet to be used to compare pyomyositis-inducing strains of staphylococci to other strains. Infection with HIV appears to predispose to pyomyositis, but rigorous data in this regard is not available. In HIV and other compromised patients a wide variety of organisms, mostly gram-negative bacilli, have been isolated.

Acute abscess is by far the most common clinical presentation. Small numbers of patients may present early with muscle pain, low-grade fever, and very hard rubber stiffness on palpation, and 5% or so may present very late with septicemia and advanced disease. Large muscles of the limbs and trunk are most often involved. Involvement of the abdominal wall muscles or psoas may cause diagnostic confusion with intra-abdominal sepsis. Lymphadenopathy is rare. Recurrent disease does occur. Leucocytosis and elevated ESR are common but serum levels of muscle enzymes remain normal. Where available ultrasound, CT, or MRI are extremely useful in localizing pockets of pus, and make trials of guided percutaneous drainage procedures possible. Once pus has begun to form, a drainage procedure is mandatory. Intensive antibiotic therapy alone never suffices. In extensive disease the whole muscle belly can be replaced by pus. Fortunately, appropriate treatment generally results in no residual functional limitations.