Dermatologic Manifestations of Mycetoma Clinical Presentation
- Author: Oliverio Welsh, MD DrSc; Chief Editor: Dirk M Elston, MD more...
History
Mycetoma occurs most commonly in people who work in rural areas where they are exposed to acacia trees or cactus thorns containing the etiologic agents that normally live as saprobes. However, the disease has also been found in individuals who work in the city in various occupations.
If left untreated, mycetoma can affect the underlying bones, joints, or adjacent organs.
Physical
Examination typically reveals a painless firm tumefaction of the affected area.
The skin is usually darker and firmer than the surrounding areas.
Nodules, abscesses, and fistulae draining a clear viscous or purulent exudate can be observed.
Granules of the microorganisms may occasionally be seen with the naked eye, as in the case of mycetoma caused by A madurae and M mycetomatis among others.
The most common anatomical locations affected by this disease are the arms and legs, particularly the feet and legs. In Mexico, the next most commonly affected site is the thoracic area, but this varies from country to country. Rarely, mycetoma can also be observed on the buttocks, the groin, the head, and the neck. See the images below.
Actinomycetoma of the foot (left) and arm (center) caused by Nocardia brasiliensis. Multiple nodules and fistulae are present. Microscopic examination of the pus (right). Granules are observed, which are multilobulated and surrounded by abundant clubs. 
Eumycetoma. Mycetoma of the hand (left). Microscopic features of a Madurella mycetomatis grain are observed (center). Notice the presence of brownish hyphae and intercellular cement (hematoxylin and eosin stain). Macrocolony of another eumycotic agent, Pseudallescheria boydii (right). Causes
Eumycetomas can be produced by a variety of fungi (see Table 1); however, actinomycetomas are mainly produced by bacteria of 4 genera: Nocardia, Actinomadura, Streptomyces, and Nocardiopsis (see Table 2), the last of which is rarely found.
Although traditionally it has been considered that mycetoma is produced by the pathogenic characteristics of the causative agents, it has recently been observed that genetic polymorphisms involved in neutrophil function are related to either the production of human mycetoma or its size, in the case of M mycetomatis infection. IL-8 (CXCL8), its receptor CXCR2, thrombospondin-4, nitric oxide synthase, and complement receptor 1 have significant differences in mycetoma patients compared with geographically and ethnically matched controls. These findings open the possibility that certain individuals are predisposed to this infection.[7]
Table 1. Fungi Causing Mycetoma (Open Table in a new window)
| White grain | Black grain |
| Acremonium falciforme | Exophiala jeanselmei |
| Acremonium kiliense | Madurella grisea |
| Acremonium recifei | M mycetomatis |
| Cylindrocarpon destructans | M pseudomycetomatis |
| Fusarium moniliforme | Leptosphaeria tomkinsii |
| Fusarium solani | Leptosphaeria senegalensis |
| Neotestudina rosatii | Pyrenochaeta mackinnonii |
| Pseudallescheria boydii | Pyrenochaeta romeroi |
| ---------------- | Phlenodomus avramii |
Table 2. Microorganisms Causing Actinomycetomas in Humans (Open Table in a new window)
| Etiologic agent | Grain |
| A madurae | White, large, 1-5 mm in diameter |
| A pelletieri | Red, hard, 1 mm in diameter |
| N brasiliensis | White to yellow, multilobed, soft, < 0.5 mm in diameter |
| N asteroides | Uncommon, white, soft, < 0.5 mm in diameter |
| Nocardia otitidiscaviarum | White to yellow, lobed, < 0.5 mm in diameter |
| Nocardia transvalensis | White to yellow, < 0.5 mm in diameter |
| Nocardia veterana[8] | -- |
| Nocardia mexicana[9] | -- |
| Nocardiopsis dassonvillei | White to yellow, < 0.5 mm in diameter |
| S somaliensis | Yellow, hard, 2 mm in diameter |
| Streptomyces sudanensis | Yellow, hard, 2 mm in diameter |
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| White grain | Black grain |
| Acremonium falciforme | Exophiala jeanselmei |
| Acremonium kiliense | Madurella grisea |
| Acremonium recifei | M mycetomatis |
| Cylindrocarpon destructans | M pseudomycetomatis |
| Fusarium moniliforme | Leptosphaeria tomkinsii |
| Fusarium solani | Leptosphaeria senegalensis |
| Neotestudina rosatii | Pyrenochaeta mackinnonii |
| Pseudallescheria boydii | Pyrenochaeta romeroi |
| ---------------- | Phlenodomus avramii |
| Etiologic agent | Grain |
| A madurae | White, large, 1-5 mm in diameter |
| A pelletieri | Red, hard, 1 mm in diameter |
| N brasiliensis | White to yellow, multilobed, soft, < 0.5 mm in diameter |
| N asteroides | Uncommon, white, soft, < 0.5 mm in diameter |
| Nocardia otitidiscaviarum | White to yellow, lobed, < 0.5 mm in diameter |
| Nocardia transvalensis | White to yellow, < 0.5 mm in diameter |
| Nocardia veterana[8] | -- |
| Nocardia mexicana[9] | -- |
| Nocardiopsis dassonvillei | White to yellow, < 0.5 mm in diameter |
| S somaliensis | Yellow, hard, 2 mm in diameter |
| Streptomyces sudanensis | Yellow, hard, 2 mm in diameter |
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