title: Application of C4d Immunohistochemistry on Routinely Processed Tissue Sections for the Diagnosis of Autoimmune Bullous Dermatoses.
abstract: The diagnosis of autoimmune bullous dermatoses relies greatly on direct immunofluorescence (DIF) examination performed on frozen tissue sections, showing deposits of immunoglobulins and/or C3 on specific cutaneous structures. However, frozen material is not always available for DIF; therefore, alternative techniques are needed in the diagnostic procedure. We therefore tested the usefulness of C4d immunohistochemistry on formalin-fixed, paraffin-embedded tissue sections for the diagnosis of bullous pemphigoid (BP) and pemphigus (P). A retrospective immunohistochemical study was performed on biopsies of BP (n: 29) and P (n: 22, including 19 Pemphigus vulgaris and 3 paraneoplastic), submitted for routine histological examination and compared with DIF on the corresponding frozen sections. Twenty-five BP biopsies (86.2%) showed C4d deposits seen as a linear labeling along the dermal-epidermal junction and on the membrane of basal keratinocytes. Seventeen P biopsies (77.2%) showed C4d deposits in a classical "intercellular" pattern, predominating on the lower epidermal layers. The sensitivity, specificity, positive predictive value, and negative predictive value reached 86%, 98%, 96%, and 92% in BP, respectively and 77%, 98%, 94%, and 92% in P, respectively. Furthermore, in the cases where serological tests were available, the sensitivity of C4d detection was higher than that of enzyme-linked immunosorbent assay/indirect immunofluorescence in both BP (87% vs. 67%) and P (82% vs. 54.5%). We conclude that DIF on frozen sections still remains the gold standard for the immunopathological diagnosis of BP and P; however, in the absence of frozen material, C4d immunohistochemistry performed on routinely processed biopsy material can be of considerable help in confirming the diagnosis.
authors: Departments of *Dermatology, and †Pathology, Edouard-Herriot Hospital, Lyon University, Lyon, France.
authors: Axel P
authors: AP
authors: Villani
authors: Brigitte
authors: B
authors: Chouvet
authors: Jean
authors: J
authors: Kanitakis
mesh_terms: D001327:Autoimmune Diseases / Q000175:diagnosis*; D003181:Complement C4 / Q000032:analysis*; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods*; D016612:Paraffin Embedding; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D012872:Skin Diseases, Vesiculobullous / Q000175:diagnosis*
chemical_list: D003181:Complement C4