Mycetoma is a chronic infection in the skin caused by either bacteria ( actinomycetoma) or fungi ( eumycetoma), typically resulting in a triad of painless firm skin lumps, the formation of weeping sinuses, and a discharge that contains grains. ^[1] 80% occur in feet. ^[1]

Most eumycetoma is caused by M. mycetomatis, whereas most actinomycetoma is caused by N. brasiliensis, S. somaliensis, A. madurae and Actinomadura pelletieri. ^[1] People who develop mycetoma likely have a weakened immune system. ^[1] It can take between 3 months to 50 years from time of infection to first seeking healthcare advice. ^[1]

Diagnosis requires ultrasound and fine needle aspiration. ^[1]

While most cases of mycetoma occur in Sudan, Venezuela, Mexico, and India, its true prevalence and incidence are not well-known. ^{[2] [3]} It appears most frequently in people living in rural areas, particularly in farmers and shepherds, who are often men between 20 and 40 years earning the primary incomes for their families. ^[1] It has been reported since 1840. ^[4] Noteworthy, the diagnosis of mycetoma in non-endemic or low endemic areas as Europe and North Africa is challenging. ^{[5] [6]} Physicians in these areas are usually unfamiliar with the disease-specific manifestations and need to exercise extra vigilance regarding those patients who are at high risk of contracting mycetoma infections. ^[7] Recent evidence suggests that Egypt, which borders sub-Saharan Africa, is a low-endemic country. ^[5] Additionally, recent evidence suggests that Pakistan, which borders India, is a moderate-endemic country. ^[8] Unlike bacterial acute hematogenous osteomyelitis and septic arthritis, misdiagnosed or delayed diagnosis of mycetoma osteomyelitis can result in amputation or radical resection. ^[5] The disease is listed by the World Health Organization (WHO) as a neglected tropical disease. ^[3]

Frequent exposure to penetrating wounds by thorns or splinters is a risk factor. ^[9] This risk can be reduced by disinfecting wounds and wearing shoes. ^[10]

Mycetoma is caused by common saprotrophs found in the soil and on thorny shrubs in semi-desert climates. ^[10] Some common causative agents are: ^[11]

• Madurella mycetomatis (fungus)
• Nocardia brasiliensis (bacteria)
• Actinomadure madura (bacteria)
• Streptomyces somaliensis (bacteria)
• Actinomadura pelletieri (bacteria) ^[3]

Infection is caused as a result of localized skin trauma, such as stepping on a needle or wood splinter, or through a pre-existing wound. ^[10]

The first visible symptom of mycetoma is a typically painless swelling beneath the skin; over several years, this will grow to a nodule (lump). ^[9] Affected people will experience massive swelling and hardening of the area, in addition to skin rupture and the formation of sinus tracts that discharge pus and grains filled with organisms. ^[9] In many instances, the underlying bone is affected. ^{[12] [10]} Some people with mycetoma will not experience pain or discomfort, while others will report itching and/or pain. ^[9]

There are currently no rapid diagnostic tools for mycetoma. ^[3] Mycetoma is diagnosed through microscopic examination of the grains in the nodule and by analysis of cultures. ^[10] Since the bacterial form and the fungal form of mycetoma infection of the foot share similar clinical and radiological features, diagnosis can be a challenge. ^[2] Magnetic resonance imaging is a very valuable diagnostic tool. However, its results should be closely correlated with the clinical, laboratory and pathological findings. ^{[12] [13]}

Currently, itraconazole is used for the treatment of mycetoma. Recent research found fosravuconazole can also be used to treat the disease. ^[14]

While treatment will vary depending on the cause of the condition, it may include antibiotics or antifungal medication. ^[9] Actinomycetoma, the bacterial form, can be cured with antibiotics. ^[2] Eumycetoma, the fungal form, is treated with antifungals. ^[13] Surgery in the form of bone resection may be necessary in late presenting cases or to enhance the effects of medical treatment. ^[12] In the more extensive cases amputation is another surgical treatment option. ^{[15] [10]} For both forms, extended treatment is necessary. ^[2]

Mycetoma is endemic in some regions of the tropics and subtropics. ^[1] India, sub-Saharan Africa as Sudan, and Mexico are most affected. ^{[1] [16]} Pakistan is probably a moderate-endemic country. ^[8] Sporadic cases have been reported across some North African countries. ^[17] Egypt is probably a low-endemic country. ^[5]

In cats, mycetoma can be treated with complete surgical removal. Antifungal drugs are rarely effective. ^[18]

• DermNet NZ: an online resource about skin diseases from the New Zealand Dermatological Society Incorporated.
• Orphanet: a reference portal from Europe that provides information on rare diseases and orphan drugs.
• ClinicalTrials.gov: a list of clinical trials related to mycetoma.