Cutaneous tuberculosis (CTB) is an uncommon form of extrapulmonary tuberculosis (TB). It is characterized as an invasion of the skin by Mycobacterium tuberculosis and, less commonly, Mycobacterium bovis and the bacilli Calmette-Guerin vaccine. Cutaneous TB is rare despite the high prevalence of TB worldwide. The highest incidence of CTB is in underdeveloped, resource-poor countries. With some exceptions, lupus vulgaris (LV) is the most common form. Cutaneous TB manifests a wide spectrum of clinical presentations, and current classification systems are based on the route of transmission and the immunologic state of the host. The exogenous (or primary) form of CTB occurs via traumatic direct inoculation of M. tuberculosis into the skin or mucous membranes leading to primary cutaneous TB, TB verrucosa cutis, and rarely LV. The endogenous (or secondary) form of CTB occurs through lymphatic, hematogenous, or contiguous spread of M. tuberculosis to the skin from an internal focus leading to the development of LV, scrofuloderma, TB cutis orificialis, miliary TB, and metastatic TB abscesses. Tuberculids are another form of CTB resulting from a hypersensitivity reaction to an internal source of M. tuberculosis antigens. Diagnosis can be made based on history, morphologic features, and histopathologic characteristics but can be complicated and substantially delayed because of the resemblance to other dermatologic conditions. Furthermore, skin biopsy and/or acid-fast bacilli staining and culture may fail to reveal the presence of M. tuberculosis. As with TB of other organs, treatment of CTB requires a 4-drug chemotherapeutic regimen that usually consists of rifampin, isoniazid, pyrazinamide, and ethambutol for 2 months followed by a 2-drug regimen for 4 months. Depending on the type of CTB, several years of chemotherapy and/or surgical excision may be needed.
From the *H. Lee Moffitt Cancer Center and Research Institute and †Division of Infectious Disease and International Medicine, College of Medicine, and ‡Division of Infectious Disease and International Medicine, College of Nursing, University of South Florida, Tampa, FL.
Correspondence to: John N. Greene, MD, FACP, H. Lee Moffitt Cancer Center & Research Institute, University of South Florida College of Medicine, 12902 Magnolia Dr, FOB-3, Tampa, FL 33612-9497. E-mail: email@example.com.
Jonathan Kass is a medical student at the College of Medicine, University of South Florida, Tampa, Fla.
The authors have no funding or conflicts of interest to disclose.