Cutaneous tuberculosis

The wide clinical spectrum of cutaneous TB depends on the route of infection (exogenous or endogenous), the host immune response and whether the subject has had previous sensitization to TB. M. tuberculosis is the main organism responsible for cutaneous TB; M. bovis can occasionally be implicated and, more rarely, the bacille Calmette-Guérin, an attenuated form of M. bovis. TB must always be considered a systemic disease, even when it is localized at the skin and even when the skin is the entry portal of the tubercle bacillus. The immunoallergic response of the organism following on from the skin infection by mycobacteria is proof of the systemic involvement that follows the localized disease