The presence of ESAT-6 and CFP 10 proteins, which are the most immunogenic proteins of the Esx-1 system and have been widely investigated for the immunodiagnosis of tuberculosis, in some <i>Mycobacteriaceae</i> and in <i>Mycobacterium leprae</i>, poses limitations for their use in specific diagnoses of TB. This evidence concerns the gene ESX1 and tuberculosis.