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]
Risk
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]
Pathogenesis
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]
Diagnosis
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]
Treatment
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.[14][10] For both forms, extended treatment is necessary.[2]
Epidemiology
Mycetoma is endemic in some regions of the tropics and subtropics.[1] India, Sub-Saharan Africa as Sudan, and Mexico are most affected.[1][15] Pakistan is probably a moderate-endemic country.[8] Sporadic cases have been reported across some North African countries.[16] Egypt is probably a low-endemic country.[5]
Other animals
In cats, mycetoma can be treated with complete surgical removal. Antifungal drugs are rarely effective.[17]