[Buruli ulcer: risk of bone involvement! Apropos of 33 cases observed in Benin]

Skin lesions are the best known manifestations of Mycobacterium ulcerans infection. However osteomyelitis is not uncommon with incidences as high as 14 p. 100 having been reported. The literature contains little specific data on bone lesions. This report describes a series of 33 patients presenting bacteriologically and/or histologically confirmed osteomyelitis induced by Mycobacterium ulcerans. In 64 p. 100 of cases, bone involvement occurred within the first year of the disease. In 70 p. 100 of cases, the site of involvement was on extremities. The median number of sites per patient was two (range, 1 to 5) and the number of bones was not correlated with the duration of disease. Overall, 41 p. 100 of bone sites occurred locally beneath skin lesions and 59 p. 100 were distant metastases. Osteomyelitis was associated with other germs in only 16 p. 100 of cases and superinfection was not a prerequisite for development of bone involvement. Clinical manifestations were usually low-grade with non-inflammatory, slightly painful local mass. The patient's general health status was unaffected in 79 p. 100. Histological examination allowed identification of the type of bone lesions induced by Mycobacterium ulcerans. For the first time, bone biopsy specimens were cultured. Based on bacteriological and histological findings, several postulations can be made about underlying pathophysiological mechanisms. The role of Buruli toxin is dealt with in the discussion.