Aspects histopathologiques de l'infection à Mycobacterium marinum

The originality of this series consists of bacteriological proof of M. marinum infection and the absence of biopsy selection based on clinical criteria. It shows that the typical granulomas are in fact present in less than two third of cases, and that these may be confused with rheumatoid nodules. The chief characteristic of these lesions is the very low concentration of microorganisms present, in contrast with other forms of mycobacterium, making them difficult to see; routine confirmation cannot thus be expected from specific staining procedures. In one case out of five, the infiltrate suggested no infectious origin, although deep skin biopsies and synovial biopsies provided more information. For all forms of necrotic granuloma, whether or not accompanied by collections of neutrophils, a culture should be carried out in a specific medium, even in the absence of microscopic evidence of bacilli.