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S I N G A P O R E M E D I C A L J O U R N A L
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Clinics In Diagnostic Imaging (26)
P Corr
CASE REPORT
A 40-year-old African man presented with a painful swelling of his right foot. The swelling developed following minor trauma to the sole of the foot six months previously while playing football barefoot. Clinical examination confirmed a grossly swollen right foot, with nodular skin thickening and sinus formation plantarly. Black granules were noted in the sinus discharge. Radiographs (Fig 1) were performed. What is the diagnosis?
IMAGE INTERPRETATION
The radiograph (Fig 1) demonstrates
marked soft tissue swelling of the forefoot with “punched-out” erosions
of the metatarsals with cortical thickening and sclerosis (arrows). Destructive
osteolysis of the tarsal bones is better appreciated on the oblique view.
Features were suggestive of chronic osteitis.
DIAGNOSIS
Madura foot (or mycetoma)
CLINICAL COURSE
The skin biopsy and culture of the sinus confirmed mycetoma infection
with Streptomycetes madurae. The patient was treated with oral anti-fungal
agents and surgical debridement with amputation of the affected toes. He
made a complete recovery.
DISCUSSION
Mycetoma describes a chronic granulomatous disorder due to fungal or
actinomycetes infection. The actinomycotic mycetoma is caused by aerobic
actinomycetes such as Nocardia brasilensis and Streptomycetes madurae while
the mycotic group are caused by true fungi such as Madurella mycetomii.
The infection is often introduced by foreign body innoculation such as
a thorn or from minor injury. It is common where patients walk bare-footed.
It was first described by Gill in Madura, India and hence the expression
“Madura Foot”. This lesion is however prevalent throughout tropical Africa,
Saudi Arabia, India, Central and South America(1,2).
The foot is the most commonly infected region, followed by the hand
and retroperitoneum(3).
There is usually a long asymptomatic incubation period, followed by the
formation of a subcutaneous granuloma. This spreads by contiguity into
deeper soft tissues such as the plantar aponeurosis and muscles. Lymphatic
spread to regional lymph nodes is common. Skin sinus formation is common
with pus discharge which characteristically contains fungal granules. Subcutaneous
nodules and abscesses may also be seen.
Bone involvement is common(3).
There is contiguous spread from the infected soft tissues, with development
of cortical erosions and periosteal reaction (Fig
1). The development of marked sclerosis is common, particularly in
those patients infected with actinomycetes, Streptomyces pelletieri and
madurae(2) (Fig
2). In some patients, there is diffuse osteopaenia with marked bony
and cartilage destruction which may be mistaken for neurogenic arthropathy(4)
(Fig 3).
Treatment depends on the causative organism. Actinomycotic soft tissue
infections are usually treatable with antibiotics while mycotic infections
are more resistant to antifungal agents(3).
Once bone is infected, surgical excision is necessary(5).
Therefore the early radiological detection of bone infection is important
for correct patient management.
ABSTRACT
A 40-year-old African man presented with a painful swollen right foot,
with a plantar discharging sinus. Radiographs showed punched-out erosions
of the metatarsals with surrounding sclerosis, consistent with Madura foot
or mycetoma. The pathogenesis and radiological features of this entity
are reviewed. Treatment is effective but the diagnosis is often considered
late in the disease at the time of biopsy. Radiologists working in endemic
regions must consider this condition in the differential diagnosis of chronic
osteitis.
Keywords: chronic osteitis, fungal infection, madura foot, mycetoma,
osteomyelitis.