Myzetome B47.9

Gill, 1842; Godfrey 1846; Carter, 1861

Indolent, chronic granulomatous infection of the skin and subcutis (myceteomas are only found on the skin!) with circumscribed, tumour-like, sometimes monstrous, purulent swellings (pseudotumour), mostly with fistulae and characteristic formation of granules (grains, drusen), which are expelled to the outside by fistula ducts. In case of an infestation of the feet one speaks of "Madura foot".

Mycetoma is caused by fungi (eumycetoma) or fungus-like bacteria (actinomycetoma). Based on the color of the granules typical for the disease group, the following pathogens can be inferred:

• In the case of black granules (caused by blackening fungi): Madurella mycetomi, Madurella grisei, Leptosphaeria senegalensis, Pyrenochaeta romeroi.
• For light granules: Allescheria boydii, Cephalosporium falciforme or Cephalosporium recifei.
• Also: Nocardia brasiliensis ( Nocardiosis)
• in rare cases dermatophytes.

A distinction is made according to the pathogen and the colour of the granules:

• Eumycetomes:
  • Pathogens are, for example: Madurella grisea and mycetomatis, Aspergillus spp., Acremonium spp., Leptosphaeria spp, Pseudallescheria spp. Fusarium solani; Exophiala jeanselmei, Sarocladium kiliense, Acremonium blochii, Aspergillus nidulans, Fusarium incarnatum, Scedosporium apiospermum complex, Curvularia lunata, Medicopsis romeroi (Dubey N et al. 2019).
  • Very rare are reports of mycetomes by dermatophytes (e.g. Trichophyton tonsurans).
• Actinomycetomes (actinomyotic myceteomes):
  • Radiation bacteria like actinomyces, Nocardia, Streptomces.
• Schizomycetomes or "botromycotic mycetomes" (Staphylococcus spp., Escherichia coli, Proteus spp., etc.).

Myzetomes are a rarity in Europe, but they are endemic in India and South America. Furthermore, they can be found in the tropical and subtropical countries of Africa (Myzetome belt between the 15th and 30 degrees northern latitude/Senegal-Sudan). Eumycetomes and actinomycetomes are distributed differently: in Mexico there are mainly actinomycetomes, in Africa eumycetomes.

Males are 5 times more frequently affected than females.

Preferably occurs in exposed rural populations by walking barefoot.

Penetration of the pathogens through small skin injuries(injury mycosis) mostly when walking barefoot (lower extremity is the typical localization). Pathogens that colonize spines or other parts of plants are inoculated into the skin. Mycetomas caused by dermatophytes (e.g. Trichophyton mentagrophytes var. interdigital) usually develop under immunosuppression.

Mainly occurring on the feet (Madura foot) (70%), less frequently hands are affected; rarities are found in other parts of the body (abdomen, face, oral cavity). The first lesion is usually found between the 1st and 2nd metatarsal bone.

Initially, after a mostly (for months past) unnoticed injury, a 0.2-0.5 cm large, not painful, subcutaneous, firm, skin-coloured induration is found on one side of the sole of the foot, between the 1st and 2nd metatarsal bone (injury mycosis). In the following months the infection spreads to the subcutis of the foot, recognizable by the increasing solid induration of the affected area. The overlying skin initially remains freely movable. Later, painless nodules (pseudotumours) develop. Abscess formation and fistula tracts with emptying of light or black granulae (drusen/grains = microcolonies) occur.

The infection can spread from the skin over years. As the muscles, nerves and tendons remain resistant to the infection for a long time, the function of the foot is maintained for a long time! Regional lymph nodes may be enlarged. A hematogenous sowing of the pathogens is omitted.

The progression takes place per continuitatem also on tendons, muscles and bones. The process ultimately becomes painful and leads to functional limitations. Internal organs are otherwise not involved! Characteristic are fistula openings in the shapelessly swollen extremity, from which pus empties under pressure.

Mycetomas are not accompanied by systemic reactions such as fever, leukocytosis, anaemia or weight loss. Little is known about a systemic immune response.

Formation of cutaneous and subcutaneous abscesses. Pathogens are detectable in the form of microcolonies (drusen). These consist of dense clusters of pathogens and appear clinically as visible granulae in the abscess side. In older foci, granulomatous epitheloid cell reactions with giant cells occur.

Typical clinic for patients with a correspondingly disposition and a long course over many years. Localization!

Detection of the 0.1-0.5 cm large, differently coloured drusen (recognisable as granules) in the fistula fluid.

Microscopic or cultural pathogen detection (see mycoses below).

Radiological changes are only detectable in a late phase of the disease. Nuclear spin examinations are better suited to detect early changes. A typical sign of a "dot in circle" is a 0.2-0.5 cm hyperintense lesion surrounded by fibrosed tissue.

Endemic Kaposi's sarcoma: Histology is conclusive.

• Charcot foot ( arthropathy, Charcot arthropathy): Polyneuropathic, chronic, mutilating joint disease, as a late complication of diabetes mellitus (mainly occurring in diabetic polyneuropathy ).
• Osteomyelitis: pathogen detection
• Tuberculosis: Pathogen detection
• Botryomycosis: also detection of granules. Kinic picture very similar, but systemic infestation. Common in immunocompromised patients: HIV infection, diabetes mellitus, immunosuppressive therapy, cystic fibrosis, osteomyelitis. Pathogen detection.
• Spinocellular carcinoma: Histology is conclusive.

• Actinomycetoma: Antibiosis after antibiogram. Bacterially induced myceteomas are generally easier to control than eumycetomas. Therapy with streptomycin sulfate and dapsone has proven to be effective; alternatively streptomycin sulfate and trimethoprim/sulfmethoxazole.
• Eumycetomes: Ketoconazole (e.g. Nizoral 400 mg/day) shows the best results, especially in infections with Madurella mycetomatis. Therapy duration: Months to years (beyond healing), depending on the pathogen also in combination with antibiotics. Resistances are frequent in Pseudoallescheria boydii or Acremonium species. In selected cases antimycotics such as itraconazole (e.g. Sempera) or griseofulvin (e.g. grivulvin) and terbinafine (high dosage of 1000 mg/day p.o.) are useful. Also with Terbinafine in high dosage (1000mg/day p.o.) satisfactory results could be achieved. Eumycetomas are difficult to treat overall and usually require long-term therapy.
• Posaconazole: In case of resistance to therapy or patients with intolerance to other systemic antimycotics: 2 times/day 400 mg (10 ml) p.o. (daily dose: 800 mg) or 4 times/day 200 mg (5 ml) p.o. The duration of therapy depends on the severity of the disease, recovery from immunosuppression and clinical response, if applicable.
• Schizomycetomas: antibiotics depending on the resistance status.

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