Cutaneous tuberculosis: diagnosis and treatment.

As we move into the 21st century, cutaneous tuberculosis has re-emerged in areas with a high incidence of HIV infection and multi-drug resistant pulmonary tuberculosis. Mycobacterium tuberculosis, Mycobacterium bovis, and the BCG vaccine cause tuberculosis involving the skin. True cutaneous tuberculosis lesions can be acquired either exogenously or endogenously, show a wide spectrum of morphology and M. tuberculosis can be diagnosed by acid-fast bacilli (AFB) stains, culture or polymerase chain reaction (PCR). These lesions include tuberculous chancre, tuberculosis verrucosa cutis, lupus vulgaris, scrofuloderma, orificial tuberculosis, miliary tuberculosis, metastatic tuberculosis abscess and most cases of papulonecrotic tuberculid. The tuberculids, like cutaneous tuberculosis, show a wide spectrum of morphology but M. tuberculosis is not identified by AFB stains, culture or PCR. These lesions include lichen scrofulosorum, nodular tuberculid, most cases of nodular granulomatous phlebitis, most cases of erythema induratum of Bazin and some cases of papulonecrotic tuberculid. Diagnosis of cutaneous tuberculosis is challenging and requires the correlation of clinical findings with diagnostic testing; in addition to traditional AFB smears and cultures, there has been increased utilization of PCR because of its rapidity, sensitivity and specificity. Since most cases of cutaneous tuberculosis are a manifestation of systemic involvement, and the bacillary load in cutaneous tuberculosis is usually less than in pulmonary tuberculosis, treatment regimens are similar to that of tuberculosis in general. In the immunocompromised, such as an HIV infected patient with disseminated miliary tuberculosis, rapid diagnosis and prompt initiation of treatment are paramount. Unfortunately, despite even the most aggressive efforts, the prognosis in these individuals is poor when multi-drug resistant mycobacterium are present. An increased awareness of the re-emergence of cutaneous tuberculosis will allow for the proper diagnosis and management of this increasingly common skin disorder.