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Osteomyelitis develops either from direct skin or subcutaneous infection involving bone or, more often, by hematogenous dissemination. Red marrow areas such as the ends of long bones, the pelvis, spine, sternum and rib cage are most commonly affected. The early changes in bone associated with soft tissue infection are erosion of the cortical surface and localized osteoporosis with little or no periosteal reaction. The osteoporosis may be quite severe and, as the cortex is destroyed, there is further mottled, patchy destruction in the underlying spongiosa. Hematogenous bone lesions tend to resemble tuberculous or fungal osteomyelitis with moth-eaten or mottled destruction but with little or no sclerosis or periosteal reaction unless draining sinuses develop (Figs. 23.23 & 23.24).

Fig. 23.23 A-C Osteomyelitis caused by B. pseudomallei involving the proximal shaft of the left humerus in a young man. A Initial AP radiograph of the left shoulder and proximal humerus on November 19, 1967 shows a long moth-eaten, lytic lesion of the humeral shaft without periosteal reaction. This appearance is typical, although not pathognomonic, of osteomyelitis because a moth-eaten pattern is also seen in malignant lesions of bone. However, B. pseudomallei was cultured from this patient. B Follow-up film of December 3, 1967 shows little change in the inflammatory process involving the humerus. C Further follow-up film of January 12, 1968 shows some reconstitution of bone with only a vague moth-eaten pattern now identified. With prolonged antibiotic therapy, there was continued regression of the osteomyelitis so that by September 1968 the bone had returned to a normal appearance radiographically. As in this case, foci of osteomyelitis in melioidosis usually resemble tuberculosis with little or no bone sclerosis or periosteal reaction unless draining sinuses develop.



Fig. 23.24 A-C Osteomyelitis of the right scapula and right acetabulum in a patient with chronic melioidosis. A Initial AP radiograph of the right shoulder on August 28, 1968 shows mottled, patchy destruction of the glenoid fossa of the scapula with slight reactive sclerosis. B Follow-up film of November 25, 1968 shows a more defined destructive process involving the glenoid fossa with increased reactive sclerosis and an apparent small sequestrum in the lower portion of the lytic area. There is also slight osteoporosis of the humeral head and shaft. C AP radiograph of the right hip taken on October 28, 1968 shows a patchy, destructive lesion involving the acetabulum with mottled areas of sclerosis within this well defined focus of osteomyelitis. D Histological section of B. pseudomallei osteomyelitis. The chronic infection is characterized by a combination of necrosis and granulomatous inflammation. The caseous appearance of the necrosis resembles tuberculosis. AFIP 69-5773.

Large abscesses may sometimes be seen, especially in the thorax where a paravertebral abscess or an extrapleural soft tissue mass involving the ribs may be present. Aspiration of an abscess or needle biopsy of bone lesions under radiological control can provide suitable material for culture of the organism.

Liver and Spleen

A liver abscess due to melioidosis may be clinically and radiologically mistaken for an amebic abscess, or other hepatic infection. Depending on the site of the abscess, the diaphragm above it will be elevated and its movement restricted. Hepatomegaly may be seen on a plain film of the abdomen. Similarly, a splenic abscess caused by B. pseudomallei may result in elevation and restricted motion of the left hemidiaphragm as well as splenomegaly (Fig. 23.25). Where such facilities are available, ultrasound, computerized tomography, MRI, angiography, or isotope scanning may aid in identifying abscesses in the liver, spleen, kidneys or brain. The imaging characteristrics of melioidosis abscesses will be indistinguishable from those of other etiologies.

In sum, melioidosis should be suspected if the following criteria are met:

1. An upper lobe pulmonary infection, with or without cavitation, or scattered small, irregular nodules on a chest roentgenogram, especially in a patient who also has multiple abscesses, draining sinuses, and evidence of bone or liver involvement.

2. A negative skin reaction and laboratory work-up for tuberculosis, histoplasmosis, or any of the other granulomatous diseases or fungi.

3. Travel or residence in Southeast Asia.


Fig. 23.25 Splenic abscess caused by B. pseudomallei in an adult man with melioidosis. (A) PA and (B) lateral views of the chest show elevation of the left hemidiaphragm from the splenic abscess beneath it. (C) Cut surface of a spleen with an acute melioidosis abscess. X60.

Differential Diagnosis

Wherever the lesions occur, tuberculosis will be the most likely initial diagnosis unless the physician is alert to the possibility of melioidosis. When suppuration is the most noticeable finding, then a fungus infection such as actinomycosis will be considered on clinical grounds, especially if the lungs are involved and tuberculosis is excluded. Moreover, the variable condition of the patients, from severely ill to completely well, will add to the confusion. Gastrointestinal symptoms may suggest dysentery, cholera or typhoid fever; amebiasis may be considered when the liver is involved and there is a lung abscess.

As with tuberculosis, the diagnosis may almost be a chance event. However it is diagnosed, melioidosis deserves proper treatment because prompt and vigorous therapy significantly lowers mortality at all stages and is absolutely crucial in the acute form of the disease. It will considerably lessen the chances of recurrence and dissemination to other organs, even in the clinically silent patient.

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