Tuberculids are a heterogeneous group of cutaneous lesions. Recent discoveries of M.
Tuberculosis DNA in these lesions by PCR suggest that M.
tuberculosis could play a role in their pathogenesis. The aim of this study was to demonstrate the presence of M.
tuberculosis DNA by polymerase chain reaction in papulonecrotic
tuberculid lesions. Skin biopsy specimens from ten patients with papulonecrotic
tuberculid lesions (histopathologic features) were studied. All of them tested solidly positive in a
tuberculin intradermal test. A gene-amplification PCR, using primers capable of amplifying
DNA in the M.
tuberculosis complex, was performed to detect M.
tuberculosis DNA in the lesions. A 285-bp sequence specific of M.
tuberculosis complex was amplified and confirmed by Southern-blot hybridation with a 32 p 5'-labelled internal probe. No inhibitors were detected in the negative PCR samples. The PCR technique makes the detection of mycobacterial
DNA in tuberculids a possibility, and therefore provides a rational basis for antituberculous
therapy and for the clinical management of these disorders.