Background Cutaneous tuberculosis has re-emerged in the last 15 years together with the higher incidence of pulmonary tuberculosis and multidrug resistance. The choice for a single diagnostic tool among the many available today is a challenge. Our objective was to compare polymerase chain reaction (PCR) with other exams in the diagnosis of cutaneous tuberculosis and atypical mycobacteria skin infection.Methods PCR and a set of five different exams were performed in 32 patients (34 samples of paraffin-embedded tissue) evaluated for 3 years in a university hospital, considering the response to mycobacterial infection treatment as a positive case.Results PCR was the most sensitive (88%) and specific (83%) exam. Culture, immunohistochemistry and acid-fast bacilli were not in agreement with clinical response to treatment.Conclusions Although PCR is a useful tool, careful clinical exam is still the gold standard for the evaluation and treatment of cutaneous tuberculosis and mycobacteria skin infection. IntroductionCutaneous tuberculosis (CT) has re-emerged worldwide together with the higher incidence of pulmonary tuberculosis and multidrug resistance in the last 15 years. [1][2][3] In Hong Kong, a retrospective survey of patients seen in public dermatology clinics found an incidence of cutaneous TB among patients of 0.07% in the period between 1983 and 1992. In a tertiary-care hospital in India, 0.1% of dermatology patients seen from 1975 to 1995 had cutaneous TB.4 Human immunodeficiency virus (HIV) infection is one cause for the increase of tuberculosis and atypical mycobacteria infection. [1][2][3][5][6][7] CT and atypical mycobacteria skin infection (AMI) present a wide range of clinical manifestations, varying from warty, nodules and papulonecrotic lesions, to ulcerations and abscesses.6 -8 Laboratory confirmation of Mycobacterium tuberculosis complex and atypical mycobacteria infection is often difficult using conventional techniques, which include acid-fast bacilli (AFB) demonstration on smears and histopathological exam, and culture. 9-11 Moreover, in paucibacillary forms, those techniques lack the sensitivity for the detection of mycobacteria. The confirmation of the diagnosis of the infection often is based solely on successful specific therapy. [12][13][14][15] Polymerase chain reaction (PCR) has emerged as a promising tool in the diagnosis of various forms of CT and atypical mycobacteria infection. 12,13,15 Published data, largely from case reports, have indicated the usefulness of PCR in the diagnosis of lupus vulgaris, scrofuloderma, and in the investigation of cases clinically suspected to be due to mycobacteria infection. [12][13][14][16][17][18][19][20][21][22][23][24][25][26][27][28] Currently, much has been published about PCR usefulness in CT and AMI diagnosis. [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] To date, there have not been any large studies published to confirm the usefulness of PCR as a routine diagnostic tool for CT and AMI. For this reason, we designed a re...

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