CLINICAL CASES   

Giornale Italiano di Dermatologia e Venereologia 2001 October;136(5):395-400

Copyright © 2001 EDIZIONI MINERVA MEDICA

language: Italian

Mycobacterium ulcerans infection (Buruli ulcer)

Tomasini C., Grassi M., Pippione M.

Università degli Studi - Torino Clinica Dermatologica II

A 11-year-old Nigerian boy in good general conditions came to our observation for the evaluation of an asymptomatic, large ulcer on the antero-lateral aspect of the left forearm and arm dating since 6 months. The ulcer showed undermined edges and the base was covered by gray-yellow necrotic tissue. Other small satellite ulcerations were also present. Anamnesis revealed that a subcutaneous nodule preceded the development of the ulcer. The patient was hospitalized. Laboratory investigations did not disclose any systemic abnormality. A swab taken from the ulcer showed many mycobacteria at immunofluorescence. The skin biopsy of the ulcer edge showed only granulation tissue with a scant granulomatous inflammation. A biopsy of the seemingly normal skin around the ulcer revealed a circumscribed area of necrosis centered in the panniculus. The necrotic fat stained deeply basophilic due to extensive calcium deposits. Nuclei of adipocytes had disappeared and numerous fatty pseudocysts were apparent. Colonies of mycobacteria were scattered diffusely throughout some of the large lacunae. Scant, if any, inflammatory infiltrate was seen. The overlying skin was intact. During hospitalization, an erythematous nodule developed on the second finger of the left hand in spite of an antibiotic therapy with rifampin. Ulcers were treated by extended excision and skin graft with a good successful rate after 6 months’ follow-up. The diagnosis of M. ulcerans infection should be considered in patiens who had been living in a tropical country with a chronic skin ulcer, particularly on an extremity, with no obvious vascular lesion. Histopathologically, infection initially produces a necrotizing panniculitis with little or absent cellular reaction despite the presence of large numbers of organisms. In chronic and/or recurrent lesions, a granulomatous reaction with relatively few organisms may occur reflecting an increasing cellular response. Calcification may also be a feature of longstanding ulcers, making identification of organisms difficult.