Mycetoma
(Maduromycosis; Madura Foot)
Mycetoma is a chronic, progressive local infection caused by fungi or bacteria and
involving the feet, upper extremities, or back. Symptoms include tumefaction and
formation of sinus tracts. Diagnosis is clinical, confirmed by microscopic examination
of exudates and culture. Treatment includes antimicrobials, surgical debridement, and
sometimes amputation.
Bacteria, primarily Nocardia sp and other actinomycetes, cause more than half the
cases. The remainder are caused by about 20 different fungal species. When caused
by fungi, the lesions are sometimes called eumycetoma.
Mycetoma occurs mainly in tropical or subtropical areas, including the southern US,
and is acquired when organisms enter through sites of local trauma on bare skin of the
feet or on the extremities or backs of workers carrying contaminated vegetation or
other objects. Men aged 20 to 40 are most often affected, presumably because of
trauma incurred while working outdoors.
Infections spread through contiguous subcutaneous areas, resulting in tumefaction and
formation of multiple draining sinuses that exude characteristic grains of clumped
organisms. Microscopic tissue reactions may be primarily suppurative or
granulomatous depending on the specific causative agent. As the infection progresses,
bacterial superinfections can develop.
Symptoms and Signs
The initial lesion may be a papule, a fixed subcutaneous nodule, a vesicle with an
indurated base, or a subcutaneous abscess that ruptures to form a fistula to the skin
surface. Fibrosis is common in and around early lesions. Tenderness is minimal or
absent unless acute suppurative bacterial superinfection is present.
Infection progresses slowly over months or years, gradually extending to and
destroying contiguous muscles, tendons, fascia, and bones. Neither systemic
dissemination nor symptoms and signs suggesting generalized infection occur.
Eventually, muscle wasting, deformity, and tissue destruction prevent use of affected
limbs. In advanced infections, involved extremities appear grotesquely swollen,
forming a club-shaped mass of cystic areas. The multiple draining and
intercommunicating sinus tracts and fistulas in these areas discharge thick or
serosanguineous exudates containing characteristic grains, which may be white or
black.
Diagnosis
Examination and culture of exudates
Causative agents can be identified presumptively by gross and microscopic
examination of grains from exudates, which contain irregularly shaped, variably
colored, 0.5- to 2- mm granules. Crushing and culture of these granules provides
definitive identification. Exudate specimens may yield multiple bacteria and fungi,
some of which are potential causes of superinfections.
Treatment
Antibacterial or antifungal drugs
Sometimes surgery
Treatment may be required for > 10 yr. Death may result from bacterial superinfection
and sepsis if treatment is neglected.
In infections caused by Nocardia (see
), sulfonamides and certain other
antibacterial drugs, sometimes in combination, are used.
In infections caused by fungi, certain potential causative organisms may be at least
partially sensitive to amphotericin B, itraconazole, or ketoconazole, but some are
resistant to all antifungal drugs. Relapses occur after antifungal therapy in most
patients, and many patients do not improve or even worsen during treatment,
indicating the often refractory nature of the infection.
Surgical debridement is necessary, and limb amputation may be needed to prevent
potentially fatal severe secondary bacterial infections.