By Gary M. White, MD
A Buruli ulcer is a serious ulcerative disease caused by infection Mycobacterium ulcerans. M. ulcerans is found in watery environments and is thought to be transmitted to humans who have contact with contaminated water. It has also been found in mosquitoes, water bugs, and crayfish. Minor trauma to the skin or bites are theorized modes of transmission, although the exact transmission pathway has yet to be elucidated. The latency period may be several months. It is common West Africa and tends to afflict the impoverished, commonly children of remote areas where modern medical services are unavailable. Histologically the necrosis extends well beyond the area colonized by the organism suggesting the Mycobacterim ulcerans exudes a toxin causing necrosis.
Multiple cases from Japan have been reported and associated with infection by M ulcerans subsp shinshuense. Cases tend to occur in areas with wetlands, ponds, lakes or stagnant water.
An indurate plaque forms and subsequently necroses, resulting in a deep ulcer usually of the extremity. Often there is a history of a penetrating trauma and without appropriate treatment, massive destruction of skin and subcutaneous tissue may occur. Although large, the ulcers tend to be painless.
Polymerase chain reaction (PCR) is used to identify the presence of M. ulcerans. PCR targeting of IS2404 is a highly sensitive and specific diagnostic test (sensitivity and specificity >90%).
Histology may show granulomatous inflammation suggestive of AFB infection. Acid-fast bacilli may be seen in biopsy specimens stained with Ziehl-Neelsen stain.
The best place to take tissue or swabs for stain or culture is the undermined edge of an ulcer. Material from the center may be negative.
Undermined edges are illustrated. World Health Organization