Identification of Mycobacterium tuberculosis DNA in a case of lupus vulgaris.

A variety of cutaneous lesions are believed to result from the presence of Mycobacterium tuberculosis. Demonstration of M. tuberculosis directly or in culture in some of these eruptions can be difficult. We studied a typical case of lupus vulgaris that had been followed for several years with frequent unrewarding biopsies and cultures to see if M. tuberculosis DNA could be demonstrated in skin biopsy specimens. We used the polymerase chain reaction and a primer/probe set specific for a region in the gene for the 65 kd antigen of M. tuberculosis to search for M. tuberculosis complex DNA. M. tuberculosis complex DNA was demonstrated in archival skin biopsy specimens from the lesion of lupus vulgaris. The polymerase chain reaction and specific primer/probe sequences can be used to demonstrate M. tuberculosis complex DNA in skin lesions. A variety of skin lesions believed to be related to tuberculosis (tuberculids) can be revisited with these techniques and studied for the presence of an infectious agent.