It may be caused by:
(1) true fungi (Eumycetes - multiple genera)
(2) actinomycetes (Actinomadura species, Streptomyces species, Nocardia species)
Risk factors:
(1) trauma to the foot, which is often bare at the time
(2) environmental contamination
(3) tropical or subtropical exposure
Clinical findings:
(1) chronic indurated swelling (tumefaction) of the foot that is often painless
(2) multiple sinus tracts
(3) purulent discharge with grains consisting of the causative micro-organisms
(4) healed scars
Eventually there may be extensive damage involving the skin, subcutaneum, muscle and bone. Chronic disability can result in disuse atrophy of the affected lower extremity.
A common finding seen on biopsy is the Splendore-Hoeppli phenomenon (an eosinophilic border around a basophilic core that consists of micro-organisms.
