The pathology of Mycobacterium ulcerans infection.

The pathology of cutaneous ulcers resulting from Mycobacterium ulcerans infection is reviewed. Initial infection causes ulceration with necrosis of the dermis and a septate panniculitis in subcutaneous fat. There is little cellular reaction despite the presence of large numbers of organisms. Recurrent or persistent infection produces a granulomatous reaction with epithelioid macrophages, variable numbers of giant cells of the Langhans type, and relatively few organisms. This type of reaction is associated with more successful treatment of the disease and appears analogous to the tuberculoid form of leprosy.