[Detection of mycobacterial DNA from paraffin-embedded tissue in lung and lymphoid epithelial granulomas]

Standard techniques for the detection of mycobacteria in granulomatous diseases can be inadequate. We analysed 71 formalin fixed and paraffin-embedded tissue blocks from 68 non-immunocompromised patients with caseating, non-caseating, scarred, and miliary granulomas of lung and lymph nodes. A reamplification PCR protocol was established to detect a 123 bp product of the repetitive insertion sequence IS986/IS6110. After exclusion of 6 PCR-negative cases with clinical sarcoidosis 97% of lung tissue blocks with more than 10% caseating and non-caseating granulomas contained mycobacterial DNA. By routine microbiology mycobacteria could be detected in 78% of the patients. Scarred granulomas were PCR-negative. All miliary granulomas were PCR-positive. Lymph nodes showed comparable results. We think that this method facilitates aetiologic analysis of granulomatous diseases especially when the suspicous tissue is fixed and microbiology is not available.