Original StudyDermal C4d Deposition and Neutrophil Alignment Along the Dermal–Epidermal Junction as a Diagnostic Adjunct for Hypocomplementemic Urticarial Vasculitis (Anti-C1q Vasculitis) and Underlying Systemic DiseaseDamman, Jeffrey MD, PhD*; Mooyaart, Antien L. MD, PhD*; Seelen, Marc A.J. MD, PhD†; van Doorn, Martijn B.A. MD, PhD‡Author Information *Department of Pathology, Erasmus Medical Center Rotterdam, Rotterdam, the Netherlands; †Department of Nephrology, University Medical Center Groningen, Groningen, the Netherlands; and ‡Department of Dermatology, Erasmus Medical Center Rotterdam, Rotterdam, the Netherlands. Correspondence: Jeffrey Damman, MD, PhD, Department of Pathology, Erasmus Medical Center Rotterdam, 's-Gravendijkwal 230, 3015 CE Rotterdam, the Netherlands (e-mail: firstname.lastname@example.org). The authors declare no conflicts of interest. The American Journal of Dermatopathology: June 2020 - Volume 42 - Issue 6 - p 399-406 doi: 10.1097/DAD.0000000000001501 Buy Metrics Abstract Urticarial vasculitis (UV) is a clinicopathologic entity characterized by persistent urticarial lesions with biopsy features of vasculitis. Currently, only certain clinical features such as arthralgia and serum complement concentrations are used to identify UV patients at risk for an underlying systemic disease. Hypocomplementemic urticarial vasculitis (HUV) is in contrast to normocomplementemic urticarial vasculitis (NUV), strongly associated with underlying systemic disease, especially systemic lupus erythematosus (SLE). The aim of this study was to find specific histopathological features associated with HUV and underlying systemic disease in UV. In addition, the use of complement C4d deposition in skin biopsies was evaluated as a diagnostic adjunct for HUV- and UV-associated systemic disease. In this retrospective study, the clinical, histopathological, and immunohistological (C4d) features of 43 patients with UV were compared between HUV and NUV and analyzed for association with UV-associated systemic disease. Eight of 43 patients with UV (19%) had hypocomplementemia. Patients with HUV showed a significantly higher number of perivascular neutrophils and lower number of eosinophils compared to NUV. Of all histopathological features, alignment of neutrophils along the dermal–epidermal junction (DEJ) and dermal granular C4d deposition were found to be strongly associated with HUV and underlying SLE. This study shows that both the alignment of neutrophils along the DEJ and dermal C4d deposition are strongly associated with HUV and SLE. Therefore, these (immuno)histopathological features can be used as an easy diagnostic adjunct for early detection of underlying systemic disease in UV. Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.