Mycetoma refers to a chronic and progressively destructive granulomatous disease within the soft tissues. The defining clinical triad comprises of a:
localised mass-like soft tissue injury
with draining sinuses
that discharge grains of contagious material
It is one of the "neglected tropical diseases" as defined by WHO 1.
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Terminology
The term "mycetoma" is also used to denote a fungus ball resulting from fungal colonisation of a pre-existing pulmonary cavity (see mycetoma (lung)) or paranasal sinus (see paranasal sinus mycetoma). The remainder of the article pertains to the soft-tissue definition of mycetoma.
Epidemiology
The disease is not notifiable. It is neglected and the true prevalence is not known.
The distribution is worldwide. Endemic areas with the highest prevalence are seen in tropical and subtropical regions ("mycetoma belt"), including 1,2:
the Indian subcontinent (Madurella mycetomatis dominates)
Africa (Streptomyces somaliensis dominates)
Central and South America (Nocardia brasiliensis dominates)
Young adults 20-40 years of age are most commonly affected. There is a male predominance, explained by occupational exposure to the outdoor environment (colonised soil and plants). Infection may also occur in travellers to endemic areas unaware of or ignoring advice 2.
Risk factors
Predisposing factors include 1,2:
low socioeconomic status
occupations with risk for contact such as farming
lack of protective clothing or shoes
Diagnosis
Diagnosis is yielded by microscopic examination of grains (either in purulent discharges or by biopsy), which is essential to perform antimicrobial susceptibility testing for treatment options.
Clinical presentation
Given the slow disease progression, painless nature, and low socioeconomic status of the most often affected patients, presentation is usually late. The classical triad of painless soft-tissue swelling, draining sinuses, and purulent discharge is considered pathognomonic.
Common sites of initial or extended infection are the extremities, back, and gluteal region.
Pathology
Infection occurs by saprophytes colonising soil or plants, inoculating via a site of minor trauma, most often in the foot, and facilitated by a lack of protective clothing or shoes (bare-footed).
The initial infection progresses to a chronic granulomatous infection with development of the characterising triad of abscesses, draining sinuses, and discharging grains in its course. Opportunistic superinfection and/or destruction of adjacent bony and visceral structures may also occur.
The infection usually remains localised but may rarely disseminate and involve any organ 3.
Aetiology
Mycetomas are subdivided by their causative agents 1:
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eumycetoma or eumycotic mycetoma
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aetiologic agent: fungi
most often Madurella mycetomatis (maduromycosis)
-
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actinomycetoma or actinomycotic mycetoma
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aetiologic agent: filamentous bacteria
most often Nocardia brasiliensis and Streptomyces somaliensis
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Radiographic features
Imaging may provide mapping of local disease extension or reveal additional sites of infection 3.
For imaging appearances see maduromycosis.
Treatment and prognosis
Possible deformation and loss of function may eventually be fatal. Treatment means are usually conservative and directed to the causative agents, however, the frequently encountered late presentation often necessitates surgery, e.g. amputation.
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