Cutaneous Tuberculosis.

Cutaneous tuberculosis (TB) may present in various clinical manifestations. Skin involvement may occur as a result of exogenous inoculation, contiguous spread from a nearby focus of infection, or by hematogenous spread from a distant focus. Because the clinical presentation of cutaneous TB can vary widely, it is important to have a high index of suspicion in appropriate clinical settings. In this chapter, the various clinical manifestations of clinical TB are classified by source of infection (exogenous, endogenous, and hematogenous spread). These are linked to the clinical appearance and histology of the skin lesions. Hopefully, this will resolve the confusion created by the myriad of terms previously used in the medical literature. Once a diagnosis of cutaneous TB is entertained, a biopsy for both culture and histopathology should be submitted. In some cases histopathology may show nonspecific inflammation without classic granuloma formation. In these cases, monoclonal antibodies and polymerase chain reaction (PCR) testing may be useful. In fact, in recent years, PCR amplification has proven to be invaluable in assisting identification of M. tuberculosis from skin biopsies in patients with negative TB cultures. In most instances, treatment of cutaneous TB requires combination chemotherapy. This is especially important in patients with extra cutaneous disease, multiple skin lesions, and those with profound immunosuppression. Surgery also may play both a diagnostic and therapeutic role.