Highlighting a Potential Pitfall Positive Treponema pallidum Immunohistochemical Stain in a Patient Without SyphilisPettit, Cory BS*; McMurray, Stacy MD†; Randall, Milton Barry MD†; Jones, Allison MD†; Fisher, Kristopher MD†The American Journal of Dermatopathology: December 2019 - Volume 41 - Issue 12 - p 924–926 doi: 10.1097/DAD.0000000000001443 Brief Report Buy Abstract Author InformationAuthors Article MetricsMetrics Abstract: The Treponema pallidum antibody immunohistochemical (IHC) stain has improved our ability to detect the organism histologically. We present a case of a man with genital condyloma acuminatum with a positive T. pallidum IHC stain but negative T. pallidum serologies and no syphilitic symptoms. It has been shown that the T. pallidum antibody IHC can cross-react, staining other spirochetes, including Borrelia burgdorferi and the Brachyspira family of intestinal spirochetes. Because of the proximity of our patient's lesions to the anus, and the persistently negative T. pallidum serologies, we believe nontreponemal spirochetes colonized the condyloma, giving a false-positive T. pallidum IHC. This cross-reactivity is a potential diagnostic pitfall and is important for the dermatopathologist to recognize, thereby avoiding false diagnosis of syphilis. *The Ohio State University College of Medicine, Columbus, OH; and †Department of Dermatology, University of Tennessee Health Science Center, Memphis, TN. Correspondence: Cory Pettit, BS, Division of Dermatology, Ohio State University Wexner Medical Center, The Ohio State University College of Medicine, 1370 Highland St. Apt E, Columbus, OH 43201 (e-mail: Cory.firstname.lastname@example.org). The authors declare no conflicts of interest. Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.