Original StudyPattern-Specific Loss of Desmoplakin I and II Immunoreactivity in Erythema Multiforme and its Variants: A Possible Aid in Histologic DiagnosisForrester, Vernon J. MD*; Tran, Benjamin BA†; Hein, Stephanie C. MD‡; Wick, Mark R. MD§Author Information *Department of Dermatology, University of Virginia, Charlottesville, VA; †University of Virginia School of Medicine, Charlottesville, VA; ‡Clear Dermatology, Inc, Ashburn, VA; and §Departments of Pathology and Dermatology, University of Virginia, Charlottesville, VA. Correspondence: Mark R. Wick, MD, Department of Pathology, University of Virginia Medical Center, 1215 Lee Street, Charlottesville, VA 22908 (e-mail: [email protected]). The authors declare no conflicts of interest. The American Journal of Dermatopathology: February 2020 - Volume 42 - Issue 2 - p 111-116 doi: 10.1097/DAD.0000000000001545 Buy Metrics Abstract Erythema multiforme (EM), Stevens-Johnson syndrome (SJS), and toxic epidermal necrolysis (TEN) comprise a family of mucocutaneous diseases associated with significant morbidity and mortality. Previous studies have confirmed the presence of autoantibodies to desmoplakin (Dp) I and II in patients with EM, SJS, and TEN. Truncated Dp production leads to characteristic changes visible on light microscopy: perinuclear clumping of keratin filaments and dyskeratotic keratinocyte. Based on these observations, the question arises as to whether a loss of Dp immunoreactivity in skin biopsies could serve as a diagnostic marker of EM, SJS, and TEN. This study analyzed Dp immunostaining patterns in 20 patients with EM or SJS/TEN. To assess the specificity of this approach, Dp immunostaining was also performed on specimens from patients with 5 potential histologic mimics of EM, SJS, and TEN. All of the samples from patients with EM, SJS, and TEN demonstrated absent or markedly diminished staining for Dp. A χ2 test demonstrated a statistically significant difference between the staining patterns in EM, SJS, and TEN and each of the other diagnostic groups that were investigated. This is the first report demonstrating statistically significant specificity of Dp staining patterns in EM/SJS/TEN as compared with other interface dermatitides. Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.