Mycetoma (Madura Foot)

Mycetoma, commonly known as Madura foot, is a chronic, scarring infection of the dermis, subcutaneous tissue and bone. It is defined by a classic clinical triad: painless swelling of granulation tissue, multiple fibrotic draining sinuses, and discharge containing fungal or bacterial grains.

Microbiologically, mycetoma has two entirely different groups of causes:

Eumycetoma (maduromycosis): true fungal mycetoma caused by structurally complex filamentous fungi.
Actinomycetoma: mycetoma caused by actinomycetes (filamentous bacteria).

Telling these two groups apart is decisive for the outlook and for saving the limb, because their treatments are completely opposite. At Haute-Derma, our approach to Madura foot combines grain analysis, histopathology with special stains and advanced imaging, with the goal of preserving as much mobility and function as possible.

Pathogenesis and Route of Infection

Entry Route and Granulation Tissue Growth

Direct inoculation through injury: the organisms enter the skin through small wounds, wood splinters or thorn pricks, or in farmers who habitually walk barefoot on humus-rich soil.
Grain formation: once in the subcutaneous tissue, the organism secretes an extracellular matrix that encases clusters of filaments, forming hard grains. This protects it from phagocytosis by the immune system and from penetration by antifungal drugs.
Deep invasion and tissue destruction: the infection does not spread through the lymphatics but advances slowly into deeper tissue, destroying fascial planes, muscle and tendon, and eventually invading bone to cause osteomyelitis, bone loss and complete deformity of the foot.

Microbiological Types and Grain Characteristics

True Fungal Mycetoma (Eumycetoma / Maduromycosis)

Accounts for about 40%–50% of mycetoma cases worldwide.

Common causative species: Madurella mycetomatis (the most common), Trematosphaeria grisea, Scedosporium apiospermum and Aspergillus spp.
Grain features:
- Black grains: usually Madurella mycetomatis (0.5–2 mm, hard, crumbling like charcoal).
- White or pale yellow grains: usually Scedosporium apiospermum or Acremonium spp.

Bacterial Mycetoma (Actinomycetoma)

Common causative species: Nocardia brasiliensis, Actinomadura madurae, Actinomadura pelletieri and Streptomyces somaliensis.
Grain features:
- Red grains: characteristic of Actinomadura pelletieri.
- Pink or ivory-white grains: usually Actinomadura madurae or Nocardia.

Comparison of Eumycetoma and Actinomycetoma

Feature	True Fungal Mycetoma (Eumycetoma)	Bacterial Mycetoma (Actinomycetoma)
Type of organism	True fungi (eukaryotes)	Actinomycetes / filamentous bacteria (prokaryotes)
Rate of progression	Very slow (years to decades)	Faster, with more marked inflammation
Grain color	Black or white/yellow	Red, yellow, pink or white
Filament width under the microscope	Broad (2–6 µm), septate fungal hyphae	Very fine bacterial filaments (under 1 µm)
Ziehl-Neelsen / Gram stain	Ziehl-Neelsen negative, Gram (-)	Usually Gram (+); Nocardia partially acid-fast
X-ray / MRI of bone	Large, well-defined lytic cavities	Diffuse lytic lesions with rapid bone destruction
Response to medical treatment	Slow; surgical debridement usually needed	Very good response to combination antibiotics

Standard Diagnostic Workup at Haute-Derma

Direct Grain Examination: pus is collected from the sinuses, or a subcutaneous abscess is gently expressed with a needle. The color, size and hardness of the grains are examined with the naked eye and under the microscope:

Crushing the grain in 10% KOH: shows broad, septate hyphae with swollen cells at the tips (eumycetoma).
Gram and Ziehl-Neelsen stains: identify fine actinomycete filaments and acid-fastness (actinomycetoma).

Skin and Subcutaneous Biopsy: the biopsy takes the full edge of a sinus tract, including the deep granulation tissue.

H&E stain: shows granulomas with central necrosis containing grains, surrounded by neutrophils, plasma cells, macrophages and a fibrous capsule.
PAS and GMS stains: highlight the hyphal walls in magenta or black within eumycetoma grains.

Imaging to Assess Depth of Invasion (X-Ray and MRI):

X-ray of the limb: assesses periosteal reaction, osteopenia and lytic cavities (geodes).
MRI: the "dot-in-circle" sign: a characteristic finding on T2-weighted images of round high-signal areas (inflamed granulation tissue) with a central low-signal dot (the grain), which helps define the exact extent of disease before surgery.

Multimodal Treatment at Haute-Derma

Medical Treatment of True Fungal Mycetoma (Eumycetoma)

Because the grains are surrounded by very thick fibrous tissue, oral antifungals must be given at high doses for a long time:

Itraconazole (first-line therapy):
- Dose: 200 mg twice daily (400 mg/day), taken right after meals.
- Duration: 6–12 months before surgery is considered, then continued for 6 months after surgery.
Voriconazole / posaconazole: used when the infection is resistant to or does not respond to itraconazole (voriconazole 200 mg twice daily).

Limb-Sparing Surgical Treatment

Conservative debulking surgery: surgery is not done first while the mycetoma is still very large. Patients receive itraconazole for at least 6 months to shrink the lesion and create a clear fibrous boundary. The surgeon then removes the entire mass while preserving as much healthy bone and tendon as possible.
Amputation: considered only as a last resort when the disease has completely destroyed the bones and joints of the foot, causing disability, or when overwhelming infection threatens life.

Frequently Asked Questions (FAQs)

+Why is it so important to distinguish true fungal mycetoma (eumycetoma) from bacterial mycetoma (actinomycetoma)?

Although the two forms look the same from the outside (a swollen foot with draining sinuses and grains in the pus), their treatments are complete opposites. Bacterial mycetoma (actinomycetoma) responds very well to combination antibiotic regimens (such as amikacin plus TMP-SMX) and can be cured with medication alone, without surgery. True fungal mycetoma (eumycetoma), on the other hand, does not respond to antibiotics at all; it needs prolonged high-dose antifungal treatment combined with surgical debridement. If eumycetoma is mistaken for actinomycetoma and treated with antibiotics, the patient can suffer severe bone destruction and may need a joint disarticulation or amputation of the foot.

+What are the earliest signs of Madura foot?

In the early stage, the disease usually begins as a small, hard, painless nodule on the top or sole of the foot, appearing some time after a thorn prick or minor injury. Because it causes no pain, burning or fever, patients often ignore it. Over months to years the nodule slowly enlarges, the overlying skin becomes stuck down and darkened, and it breaks open into sinuses that drain mucus-like fluid containing tiny black or white grains. Seeing a specialist as soon as a hard lump appears under the skin after an injury is the key to successful treatment.

+Can oral antifungals alone cure eumycetoma without surgery?

Antifungals alone very rarely cure moderate or severe eumycetoma. The grains sit deep inside pockets of pus surrounded by a very dense, avascular fibrous capsule that prevents antifungal drugs in the bloodstream from reaching the center of the lesion. The current standard of care is therefore to start with itraconazole to shrink the lesion, then surgically debride and remove all the fibrous tissue containing grains, and continue maintenance antifungal therapy afterward to kill any remaining spores.