Mycetoma is a chronic, progressive infection of the skin, underlying soft tissue, and often bone, caused by certain fungi or bacteria that enter the body through a break in the skin. It typically affects the foot, which is why it has long been called “Madura foot,” but it can appear on the hands, back, or nearly any body part exposed to contaminated soil. The infection grows slowly over months or years, producing a distinctive combination of swelling, draining channels in the skin, and tiny colored granules discharged from those channels. Despite being recognized for well over a century, mycetoma remains stubbornly difficult to treat and disproportionately affects people in low-income, rural communities across the tropics.
Two Diseases Under One Name
One of the first things to understand is that mycetoma is not a single infection. It comes in two fundamentally different forms depending on the type of organism responsible. Eumycetoma is caused by true fungi, with species like Madurella mycetomatis, Madurella grisea, and Scedosporium apiospermum among the most common culprits. Actinomycetoma, on the other hand, is caused by filamentous bacteria, including Nocardia brasiliensis, Actinomadura madurae, and Actinomadura pelletieri. The distinction matters enormously because the two forms respond to entirely different drugs and carry different prognoses. Actinomycetoma tends to respond better to antibiotics, while eumycetoma is far more resistant to available antifungal medications and more likely to end in amputation.
How People Get Infected
The organisms that cause mycetoma live in the soil and on plants. They enter the body through traumatic inoculation, meaning a puncture wound or scratch that drives contaminated material into the deeper layers of skin.1PubMed. Mycetoma: a thorn in the flesh In endemic regions, this often happens when people walk barefoot and step on thorns. A study of actinomycetoma cases in northeast Mexico found that about 35% of patients recalled a prior thorn injury involving Acacia or Prosopis plants.2PubMed Central. Climate, soil type, and geographic distribution of actinomycetoma cases in Northeast Mexico: A cross-sectional study Farmers, herders, and laborers who work outdoors without protective footwear face the highest risk. Once the organism is embedded beneath the skin, it begins to grow slowly, forming granulomas and gradually invading deeper structures.
Mycetoma is not contagious. You cannot catch it from another person or spread it through casual contact. The infection requires that specific soil-dwelling organisms be physically pushed through the skin barrier, which is why it remains a disease strongly linked to occupation and environment rather than to person-to-person transmission.
Where Mycetoma Occurs and Why
Mycetoma has a strong geographic footprint. It concentrates in a band of tropical and subtropical countries stretching across Africa, the Middle East, South Asia, and parts of Latin America. Sudan, Mexico, India, and Senegal report large numbers of cases. The environment plays a major role in shaping where the disease appears. Research mapping environmental predictors of mycetoma has found that the strongest factors include aridity, proximity to rivers and other water sources, low soil calcium and sodium levels, and the presence of various thorny tree species.3PLoS Neglected Tropical Diseases. Mycetoma and the environment Distance to the nearest river was the single strongest predictor of where eumycetoma cases cluster, followed by the diversity of thorny trees in the area.
These environmental factors are not identical for the two types. For actinomycetoma, the distance to the nearest water body such as a pond or lake mattered most, while eumycetoma occurrence was more closely tied to river proximity and the presence of specific tree species like Acacia mellifera and Faidherbia albida.4PLoS Neglected Tropical Diseases. Mycetoma and the environment Soil type also varies between clusters. In northeast Mexico, actinomycetoma cases grouped around areas with kastanozems and lithosols soils, with different causative species appearing in different soil environments.5PubMed Central. Climate, soil type, and geographic distribution of actinomycetoma cases in Northeast Mexico: A cross-sectional study All of this suggests that the organisms have specific ecological niches, and that climate change or shifts in land use could alter where mycetoma becomes more or less common.
Recognizing Mycetoma
Mycetoma typically develops on the foot, though it can occur elsewhere. The clinical hallmark is a triad: a localized, firm swelling; sinus tracts that open onto the skin surface; and the discharge of grains or granules from those sinuses.6PubMed Central. Clinical Features of Mycetoma and the Appropriate Treatment Options The grains are actually tiny colonies of the infecting organism, cemented together, and their color provides an early clue to the cause. Black grains generally point to fungal infection, while pale, yellow, or reddish grains tend to indicate bacterial causes, though there are exceptions. The swelling is usually painless in the early stages, which is a large part of the problem: patients often wait months or years before seeking care, by which time the infection has spread deep into muscle and bone.
Unusual presentations do occur. The swelling may not produce visible sinuses in the early phases, or the grains may be too small to see with the naked eye. In some cases the infection is mistaken for a benign cyst, a tumor, or even tuberculosis. This delay in recognition is one of the major barriers to successful treatment.
Diagnosis Beyond the Bedside
Identifying the specific organism behind a mycetoma case is essential for choosing the right treatment, and multiple tools are used to get there.
Grain Analysis and Histopathology
Examining the discharged grains under a microscope remains a frontline diagnostic step. Grains from different organisms have distinctive appearances when stained. For example, Madurella mycetomatis grains are light to dark brown with irregular outlines and tend to fracture during sectioning. They come in two structural types: filamentous, which is more common, and vesicular. By contrast, Actinomadura pelletieri grains stain a characteristic deep violet color, which is so distinctive it can allow diagnosis without the need for culture.7PLoS Neglected Tropical Diseases. The Accuracy of Histopathological and Cytopathological Techniques in the Identification of the Mycetoma Causative Agents Streptomyces somaliensis grains, on the other hand, are poorly stained by standard methods and can be difficult to detect. Actinomadura madurae grains range from yellow to white, making them easy to confuse with surrounding fat in tissue sections, though larger grains display a characteristic two-toned pattern with a dense purple rim and a lighter center.
Imaging
Imaging helps clinicians understand how far the infection has spread, especially into bone. MRI is the most informative tool available. A hallmark finding on MRI is the “dot-in-circle” sign: clusters of small, round, bright lesions on certain sequences, each containing a tiny dark focus at its center. This pattern reflects the granulomatous tissue surrounding the organism’s grains.8PubMed Central. The “dot-in-circle” sign in musculoskeletal mycetoma on magnetic resonance imaging and ultrasonography The same sign can often be seen on ultrasound as well, appearing as a bright central echo within a darker surrounding area.9PubMed. MRI of mycetoma of the foot: two cases demonstrating the dot-in-circle sign Ultrasound is especially valuable in resource-limited settings where MRI scanners are scarce.
Plain X-rays become important once bone is involved. A radiographic classification system describes six progressive stages of bone damage, from early external pressure on intact bone (stage I) all the way to uncontrolled multidirectional spread through the skeleton (stage VI), passing through cortical erosion, central cavitation, and longitudinal or horizontal spread along the bones of the foot along the way.10PubMed. New radiographic classification of bone involvement in pedal mycetoma This staging system helps surgeons decide how extensive an operation needs to be.
Molecular Methods
In recent years, molecular tools have become increasingly available for mycetoma diagnosis. Techniques such as PCR, DNA sequencing, and protein-based identification like MALDI-TOF mass spectrometry can identify the causative species with far greater speed and precision than culture alone.11PubMed. The developed molecular biological identification tools for mycetoma causative agents: An update Culture can take weeks and sometimes fails entirely, so molecular approaches are a significant step forward. The catch is that these technologies require equipment and expertise that are still limited in many of the rural areas where mycetoma is most common.
Treatment and Its Frustrations
Treatment depends heavily on whether the infection is bacterial or fungal, and in both cases the journey is long and uncertain.
Actinomycetoma
Actinomycetoma is the more treatable form. Various antibiotic combinations have been used, typically involving drugs like trimethoprim-sulfamethoxazole, amikacin, or dapsone. A modified two-step protocol studied in a small series showed that patients achieved complete healing of their sinuses and marked reduction in swelling during the initial intensive phase, usually within a few months. Maintenance therapy was then continued for several additional months, and most patients who followed up remained disease-free afterward, though one patient relapsed more than two years after stopping treatment.12PubMed. A modified two-step treatment for actinomycetoma These results are encouraging but come from small numbers of patients, and treatment durations are still long by any standard.
Eumycetoma
Eumycetoma is where the therapeutic picture grows darker. The standard approach has been itraconazole, an antifungal drug, typically combined with surgery. Treatment commonly lasts a minimum of twelve months, and treatment failure is frequent enough that it can lead to amputation.13PubMed. Two dose levels of once-weekly fosravuconazole versus daily itraconazole in combination with surgery in patients with eumycetoma in Sudan: a randomised, double-blind, phase 2, proof-of-concept superiority trial A large cohort from the Mycetoma Research Center in Sudan, where about three-quarters of patients had eumycetoma, reported cure rates of only around 13% for eumycetoma and about 14% for actinomycetoma despite long treatment durations.14Transactions of The Royal Society of Tropical Medicine and Hygiene. Mycetoma management and clinical outcomes: the Mycetoma Research Center experience Those numbers are sobering and reflect just how far current therapies fall short, especially for the fungal form.
The Role of Surgery
Surgery is a central part of mycetoma management, not a last resort. For small, localized lesions, wide surgical excision may be curative on its own when combined with appropriate drugs. For massive infections, surgery serves to reduce the organism load so that medications have a better chance of working. In patients with severe disease complicated by secondary bacterial infection, surgery can be life-saving.15PubMed Central. The Surgical Treatment of Mycetoma The surgical spectrum runs from debridement (cleaning out infected tissue) through wide excision all the way to amputation in the most advanced cases.
One aspect that has received more attention recently is reconstruction after surgery. Large excisions can leave significant tissue defects, and when direct skin closure is not feasible, reconstructive techniques such as skin grafts or flaps should be considered as long as amputation is not indicated.16JPRAS Open. Reconstructive surgery for mycetoma: Preliminary algorithm and a systematic review This is an evolving area, but it reflects growing recognition that simply removing infected tissue is not the end of the surgical story.
What the Immune System Does (and Does Not Do)
Researchers have been working to understand why some people develop massive, uncontrollable infections while others seem to keep the disease somewhat contained. The immune response to mycetoma involves a complex interplay of signals. Patients with mycetoma show elevated blood levels of both IL-10 and CCL5, and genetic variations in these immune molecules appear to influence whether a granuloma forms around the infection.17Medical Mycology. The association between the interleukin-10 cytokine and CC chemokine ligand 5 polymorphisms and mycetoma granuloma formation The granuloma is the body’s attempt to wall off the organism, and its success or failure shapes the clinical outcome.
Inside the granuloma itself, the inflammatory molecule IL-17A is expressed most heavily in the zones closest to the grain, and its expression is higher in larger lesions and those of longer duration. An enzyme called MMP-9, which breaks down connective tissue, follows a related pattern: its expression correlates with IL-17A levels and increases over time.18PLoS Neglected Tropical Diseases. Interleukin-17 and matrix metalloprotease-9 expression in the mycetoma granuloma This suggests that the immune response may itself contribute to tissue destruction as the disease advances, an unhelpful form of collateral damage.
Work on patients with Madurella mycetomatis eumycetoma has also shown that those who undergo surgical excision tend to have higher levels of pro-inflammatory immune signals and lower levels of anti-inflammatory ones compared to patients treated without surgery.19PLoS Neglected Tropical Diseases. Th-1, Th-2 Cytokines Profile among Madurella mycetomatis Eumycetoma Patients This shift toward a more aggressive immune profile after surgery may help explain why combining surgery with drug therapy produces better results than drugs alone, though the precise mechanism is still being investigated.
New Drugs on the Horizon
The inadequacy of existing eumycetoma treatments has pushed researchers to search for new drug candidates. A screening effort tested hundreds of compounds against five different eumycetoma-causing fungal species and then checked the most promising ones in an animal model. Only four compounds inhibited all five species, and after further testing in infected larvae, four drugs showed meaningful survival benefit: fenbendazole, ravuconazole, olorofim, and an experimental compound designated MMV1782387. Olorofim produced the highest survival rate at about a third of treated larvae still alive at ten days, compared to near-total mortality in untreated controls.20PLOS Neglected Tropical Diseases. Screening the pandemic response box identified benzimidazole carbamates, Olorofim and ravuconazole as promising drug candidates for the treatment of eumycetoma Fenbendazole and the related compound carbendazim belong to the benzimidazole carbamate class, drugs already widely used against parasites in both human and veterinary medicine. Their antifungal activity works by disrupting the internal scaffolding that cells need to divide. These are still early-stage findings, but they offer a path forward that current therapies have not provided.
Fosravuconazole, a prodrug of ravuconazole that can be taken once weekly, has moved further along in clinical testing. A randomized phase 2 trial in Sudan compared two dose levels of fosravuconazole against daily itraconazole, both combined with surgery, in patients with eumycetoma.21PubMed. Two dose levels of once-weekly fosravuconazole versus daily itraconazole in combination with surgery in patients with eumycetoma in Sudan: a randomised, double-blind, phase 2, proof-of-concept superiority trial A once-weekly pill would be a major practical advantage for patients in rural areas who struggle with daily medication compliance over many months.
The Human Cost
Mycetoma hits hardest in communities that can least afford it. The disease primarily affects young adults in their working years, and its chronic, disabling nature extracts a steep economic toll. A study of 270 patients found that nearly half reported reduced ability to sustain themselves economically because of their mycetoma. Among those who were employed or seeking employment, about 40% experienced difficulty in their work, and roughly one in six was completely unable to work for pay.22PLoS Neglected Tropical Diseases. The disabling consequences of Mycetoma The slow progression of the disease means these impacts accumulate over years, and the social stigma attached to a visibly deformed, draining foot can be isolating. In many endemic areas, patients delay seeking care not only because the early disease is painless but because healthcare facilities capable of treating mycetoma are far away and the costs of prolonged treatment are prohibitive.
Mycetoma was recognized as a neglected tropical disease by the World Health Assembly, and in response, a Global Mycetoma Working Group was formed in 2018 to connect experts and public health practitioners worldwide and accelerate prevention and treatment efforts.23Transactions of The Royal Society of Tropical Medicine and Hygiene. Development of the Global Mycetoma Working Group Progress has been real but slow. There is still no vaccine, no rapid point-of-care diagnostic test widely available in the field, and no short, reliably curative drug regimen for eumycetoma.
Reaching Patients in Remote Areas
Because mycetoma clusters in rural, often remote communities, getting care to patients requires creative approaches. The Mycetoma Research Center in Sudan has organized mobile medical missions to endemic villages, assembling teams that include surgeons, radiologists, molecular biologists, pharmacists, and support staff, as well as epidemiologists and environmental consultants who study local conditions.24PLoS Neglected Tropical Diseases. A holistic approach to the mycetoma management These missions bring diagnostic imaging, minor surgical capability, and medication directly to the places where patients live. The model is resource-intensive but addresses a practical reality: many patients simply cannot travel to tertiary centers for the repeated, prolonged care mycetoma demands. Whether this approach can be scaled to other endemic regions remains an open question, but it represents one of the few proven ways to close the gap between where the disease lives and where the expertise sits.
Mycetoma in Animals
Mycetoma is not exclusively a human disease. It has been documented in dogs, cats, horses, and other animals, and the infections mirror the human form in key respects. A case report in a young Great Dane described a large subcutaneous mass on the inner thigh that, when excised, revealed the characteristic dark grains embedded in inflamed tissue. Histological examination showed pyogranulomas surrounding pigmented fungal elements, and molecular testing identified the organism as Madurella pseudomycetomatis.25Medical Mycology Case Reports. Canine eumycetoma caused by Madurella pseudomycetomatis Animal cases are uncommon but instructive. They confirm that the causative organisms are environmental generalists, not human-adapted pathogens, and they provide additional models for understanding how the infection establishes itself and how the host immune system responds. For pet owners in endemic areas, any persistent, firm, draining mass on an animal warrants veterinary attention with mycetoma as part of the differential diagnosis.