DETECTION OF MYCOBACTERIAL DNA IN THE SKIN - ETIOLOGIC INSIGHTS AND DIAGNOSTIC PERSPECTIVES

Background: Tuberculosis may be as old as mankind and continues to be a serious medical problem today. Cutaneous tuberculosis shows consider able morphological variability, and it is included in the differential diagnosis of many other skin disorders. It is especially difficult to distinguish skin tuberculosis from other granulomatous processes of t he skin. Therefore, reliable laboratory tests are needed to confirm or rule out the diagnosis. However, the diagnostic identification of Myc obacterium tuberculosis and related organisms has remained difficult u sing conventional laboratory tests (ie, microscopy and culture).Observ ations: The diagnostic usefulness of molecular techniques, especially the polymerase chain reaction (PCR), in skin tuberculosis is reviewed, and the technical issues of PCR in general are discussed, with specia l regard to the analysis of mycobacterial DNA in skin specimens. The P CR has been successfully applied to detect DNA from M tuberculosis in lupus vulgaris and several other forms of skin tuberculosis. It has al so been used to identify mycobacterial DNA in certain forms of tubercu lids, thereby supporting the long- and often-debated tuberculous origi n of these skin disorders. Investigations of the presence of mycobacte rial DNA in cutaneous sarcoidosis have not lent support to a general r ole for mycobacteria in sarcoidosis. Conclusions: Polymerase chain rea ction-based detection of M tuberculosis DNA in skin samples may extend and improve the diagnostic panel for cutaneous tuberculosis, if the t echnique is prudently and properly used. Furthermore, PCR provides exc iting opportunities to gain further insight into the pathogenesis of c utaneous tuberculosis and other granulomatous skin diseases.