Histopathologic Features ofMycobacterium ulceransInfection

Abstract

Because of the emergence of Buruli ulcer disease, the World Health Organization launched a Global Buruli Ulcer Initiative in 1998. This indolent skin infection is caused by Mycobacterium ulcerans. During a study of risk factors for the disease in Ghana, adequate excisional skin-biopsy specimens were obtained from 124 clinically suspicious lesions. Buruli ulcer disease was diagnosed in 78 lesions since acid-fast bacilli (AFB) were found by histopathologic examination. Lesions with other diagnoses included filariasis (3 cases), zygomycosis (2 cases), ulcerative squamous cell carcinomas (2 cases), keratin cyst (1 case), and lymph node (1 case). Thirty-seven specimens that did not show AFB were considered suspected Buruli ulcer disease cases. Necrosis of subcutaneous tissues and dermal collagen were found more frequently in AFB-positive specimens compared with specimens from suspected case-patients (p<0.001). Defining histologic criteria for a diagnosis of Buruli ulcer disease is of clinical and public health importance since it would allow earlier treatment, leading to less deforming sequelae.

The local immune response in ulcerative lesions of Buruli disease

“…The histopathological features were similar to those described previously [16,17]. Epidermal hyperplasia was found at the lesion edges, as well as extensive coagulative necrosis affecting the subcutaneous tissue, with variable amounts of inflammatory cells with and without granulomas.…”

“…Thus, in the present study only ulcerative lesions were analysed. This is the form of the disease subjected most often to histopathological study [16], and all our cases showed AFB confirming the diagnosis.…”

“…The clinical characteristics of these lesions are not specific, particularly during the preulcerative stage. Due to its clinical non-specificity, and because patients usually seek medical assistance after ulcerative lesions have become well-established, it is difficult to obtain representative biopsies from pre-ulcerative and/or healed lesions [16]. Thus, in the present study only ulcerative lesions were analysed.…”

“…Thus it seems that granuloma formation represents a late event of the ulcerative stage, probably near to the phase of spontaneous healing. Moreover, granulomas in these older lesions co-existed with pseudo-epitheliomatous epidermal hyperplasia and granulation tissue, which are usually associated with chronic infection [16]. The major virulence determinant of M. ulcerans is the toxin mycolactone.…”

Buruli ulcer

“…28 Furthermore, people can spontaneously heal lesions without treatment, although a deforming scar can remain. 63 This indicates that an adaptive immune response, whether it is humoral, cellular or both, is able to control and clear the infection. However, it has not been reported whether patients who spontaneously heal lesions are left with protective memory responses, or whether they are still susceptible to re-infection.…”