Granuloma annulare - a manifestation of infection with Borrelia?

Background: Among the theories of origin of granuloma annulare (GA) are those of infection. Reports gave raise to the assumption that there is evidence for Borrelia as the causing agent. Methods: To assess the evidence for infection with Borrelia in GA, tissue sections were stained with a polyclonal Borrelia antibody. With focus-floating microscopy (FFM), slides were scanned at a 200- to 400-fold magnification. Part of the material was also investigated with a Borrelia-specific polymerase chain reaction (PCR). Results: A total of 157 biopsies of GA have been investigated. Using FFM, Borrelia were detected in 127 cases of GA (80.9%). Borrelia were more prominent in localized (85.2%) than in diffuse GA (62.1%). In 27 cases of GA analysed by PCR, Borrelia-specific DNA could be detected in only one case (3.7%), but was positive in 21 cases by FFM (77.8%). About 93.3% of 15 control cases of borreliosis were positive with FFM and 46.7% with PCR, while all controls other than borreliosis remained negative for spirochetes. Conclusion: FFM is a reliable method to show Borrelia in tissue sections of GA, which is more sensitive than PCR. This underlines the possibility that Borrelia are involved specifically in the aetiology and pathogenesis of GA.