Mycetoma is a chronic, slowly progressive infection of the skin and subcutaneous tissue that develops after trauma and subsequent contamination with soil and/or vegetation. It may also be referred to as Madura foot, eumycetoma, actinomycetoma, or exogenous actinomycosis.

The organisms that cause mycetoma come from a variety of different genera of soil-dwelling bacteria (including Nocardia, Actinomadura, Streptomyces, and Actinomyces) and fungi (including Madurella, Acremonium, Fusarium, and Aspergillus). Actinomycetoma (bacterial etiology) may progress rapidly without treatment but responds very well to antibiotic treatment. Eumycetoma (fungal etiology) carries a poorer prognosis for cure and typically requires surgery as a part of the treatment regimen. Different causative organisms predominate in different parts of the world with eumycetoma being more common in Africa and India and actinomycetoma being more common in Latin America.

Mycetoma is diagnosed most commonly in tropical, subtropical, and equatorial regions of the developing world. Mycetomas are very rare in children. Risk factors include trauma (thorn puncture, mild abrasion), skin exposure to soil and/or vegetation (often due to farming, carrying crops, walking barefoot), male sex (likely due to increased occupational exposures and possibly hormonal differences), and immunodeficiency.

Mycetomas occur most commonly on the feet and lower extremities, where trauma and subsequent soil exposure are most likely. They have been reported on other body areas less commonly (eg, hand, thigh, forearm, shoulder, and head and neck, which are often associated with carrying vegetation over the shoulder).

After initial exposure to the pathologic organism, there is an incubation period of weeks to months (actinomycetoma evolves faster than eumycetoma) before a papule or nodule develops. This slowly expands to form a tumor-like mass that develops subcutaneous abscesses. After about 6-12 months, sinuses appear, which exude purulent material of varying hues and consistencies known as granules or sclerotia.

Mycetoma is typically painless. The presence of pain implies secondary bacterial infection or osteomyelitis. Most infections remain localized and may cause significant local destruction. However, systemic spread may occur in immunocompromised individuals with development of mycetomas in internal organs.

Poorer prognosis may be associated with head lesions because they may extend intracranially.

Related topic: Endogenous actinomycosis