A chronic, progressive, local infection caused by fungi or bacteria, involving the feet, upper extremities, or back and characterized by tumefaction and formation of multiple sinus tracts. Mycetoma occurs mainly in tropical or subtropical areas, including the southern USA, and is acquired by entry of organisms through sites of local trauma on bare skin of the feet as well as on the extremities or backs of workers carrying contaminated vegetation or other objects. Men aged 20 to 40 are most often affected, presumably because of trauma incurred during work outdoors. Microscopic tissue reactions may be primarily suppurative or granulomatous depending on the specific causative agent. The first lesion may be a papule, a fixed subcutaneous nodule, a vesicle with an indurated base, or a subcutaneous abscess that ruptures to form a fistula to the skin surface.
Fibrosis is common in and around early lesions.
There is little or no tenderness in the absence of acute suppurative bacterial superinfection. Infection progresses slowly over the course of months or even years, with gradual, progressive extension to and destruction of contiguous muscles, tendons, fascia, and bones. There is neither systemic dissemination nor signs and symptoms suggesting generalized infection. Eventually, muscle wasting, deformity, and tissue destruction prevent use of affected limbs. In advanced infections, involved extremities appear grotesquely swollen, forming a club-shaped mass of cystic areas with multiple draining and intercommunicating sinus tracts and fistulas that discharge thick or serosanguinous exudates containing characteristic grains.