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Mycetoma

Mycetoma refers to a chronic and progressively destructive granulomatous disease. The defining clinical triad comprises:

  • localized mass-like soft tissue injury with 
  • draining sinuses, that 
  • discharge grains of contagious material

It is one of the 17 neglected tropical diseases defined by WHO 3.

Some authors incorrectly use the term to denote a fungus ball or conglomeration (e.g. aspergilloma), developing in a pre-existing cavity, most often lung cavities or paranasal sinuses

Epidemiology

The disease is not notifiable. It is neglected and the true prevalence is not known.

Distribution is worldwide. Endemic areas with highest prevalence are seen in tropical and subtropical regions ("mycetoma belt"), including 3, 4:

  • Indian subcontinent (Madurella mycetomatis dominates)
  • Africa (Streptomyces somaliensis dominates)
  • Central and South America (Nocardia brasiliensis dominates)

Most commonly affected are young adults, 20-40 years of age. There is male preponderance, explained by occupational exposure to outdoor environment (colonised soil and plants). ​Infection may also occur in travelers to endemic areas unaware of or ignoring advices 3, 4

Predisposing factors include 3 ,4:

  • low socioeconomic status
  • occupations with risk for contact such as farming
  • lack of protective clothing or shoes

Pathology

Infection occurs by saprophytes colonising soil or plants (see above), inoculating via a site of minor trauma, most often in the foot and facilitated by lack of protective clothing or shoes (bare-footed). 

Initial infection progresses to chronic granulomatous infection with development of the characterizing triad of abscesses, draining sinuses and discharging grains in its course. Opportunistic suprainfection and/or destruction of adjacent bony and visceral structures may also occur.

​Usually infection remains localised but it may rarely disseminate and involve any organ 5.

Definitions

Mycetomas are subdivided by their causative agents

  • Eumycetoma or eumycotic mycetoma
    • aetiologic agent fungi
  • Actinomycetoma or actinomycotic mycetoma
    • aetiologic agent filamentous bacteria
      • most often Nocardia brasiliensis and
      • Streptomyces somaliensis 
         

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 are considered pathognomonic.

‎Common sites of initial or extended infection are ‎the extremities, back and gluteal region.‎

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.

Radiographic features

Imaging may provide mapping of local disease extension or reveal additional sites of infection 5.

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 causing agents, however the frequently encountered late presentation often necessitates surgery, e.g. amputation.

See also

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