The Histologic Spectrum of the Cutaneous Mycobacterioses

The authors examined the histopathology of cutaneous involvement in 31 cases of nonleprous mycobacterial infection. Cases include three patients with Mycobacterium kansasii infection, two with M. fortuitum infections, and one each with M. marinum and M. chelonei infections, as well as 18 with M. tuberculosis infections. In the remainder, species were not identified. The histopathologic picture was variable and often did not suggest mycobacterosis. The authors identified seven basic pathologic patterns of skin involvement: 1) abscess, 2) well-formed (tuberculoid) granulomas, 3) diffuse histiocytic infiltration, 4) panniculitis, 5) nonspecific chronic inflammation, 6) naked (sarcoidal) granulomas, and 7) rheumatoid-like nodules. Intermediate forms were also found. Some cases showed adnexal or epidermal involvement, while others showed variably distributed dermal infiltration. The results indicate that a wide variety of cutaneous, clinical, and histologic guises may be assumed by mycobacterial infections in normal and immunocompromised hosts.