Cutaneous Manifestations of Mycobacterium kansasii Infection.

Purpose of Review: Mycobacterium kansasii is a slow-growing member of the nontuberculous mycobacterial species that manifests clinically with pulmonary, cutaneous, or disseminated forms. Most cases of M. kansasii infection occur in immunocompromised hosts including HIV/AIDS, solid-organ transplantation, anti-interferon-γ antibody disorder, or among those with pulmonary disorders such as chronic obstructive pulmonary disease or cystic fibrosis. In this review, we aim to discuss relevant literature regarding the clinical manifestations of this infection with a particular emphasis on the clinical spectrum and treatment of the cutaneous manifestations of this mycobacterial infection. Recent Findings: Infection caused by M. kansasii is associated with exposure to contaminated municipal water systems since this organism thrives in human-engineered environments. Chronic or subacute skin lesions may represent the primary source of entry of the organism due to open sores or traumatic injuries. Alternatively, cutaneous lesions may occur secondary to dissemination of the organism to the skin from pulmonary infection. The diagnosis of M. kansasii of the skin and soft tissues should be entertained among immunocompetent or immunocompromised individuals presenting with subacute or chronic lesions. The differential diagnosis of M. kansasii infection includes infections of skin and soft tissues caused by rapidly growing mycobacteria, subcutaneous mycosis, pyogenic bacterial infections, nocardiosis, free-living amoebas, and protothecosis. Summary: Cutaneous lesions caused by M. kansasii most commonly manifest in the setting of concomitant pulmonary disease or in the setting of disseminated infection among immunocompromised hosts. When clinicians suspect a cutaneous mycobacterial infection either due to slow-growing mycobacteria such as M. kansasii or due to rapidly growing mycobacteria, obtaining a skin biopsy of chronic nonhealing lesions for histopathologic evaluation and for microbiological assessment is crucial. Mycobacteriology assessment of clinical specimen includes acid-fast bacilli staining, culture in solid/liquid media, and molecular assays for confirmation. Treatment of M. kansasii infection of the skin and subcutaneous tissues follows the same management recommendations as those for the treatment of isolated pulmonary forms or disseminated disease.