The diagnostic roles of C4D expression in SOME AUTOIMMUNE BULLOUS DERMATOSES IN ZAGAZIG UNIVERSITY HOSPITALS; an immunohistochemical study

Abstract

Background: Autoimmune bullous skin dermatoses (AIBD) diagnosis relies on direct immunofluorescence examination performed on frozen tissue sections. However, this is not always available for DIF; therefore, alternative techniques needed for diagnosis. We tested the usefulness of C4d immunohistochemistry on formalin-fixed, paraffin-embedded tissue (FFPE) sections for the diagnosis of AIBD. Objective:to evaluate the role of C4d expression using immunohistochemistry in diagnosis of some autoimmune bullous skin diseases. Methods: This study included FFPE tissue blocks of 35 cases from archives of pathology department, Faculty of medicine, Zagazig University in the period from January 2017 to December 2017. These 35 cases were diagnosed histopathologically as: 30 cases autoimmune bullous dermatoses (18 pemphigus vulgaris, 6 bullous pemphigoid, 3 pemphigus foliaceus and 3 drug induced pemphigus) and 5 cases erythema multiforme. Specimens were obtained as punch biopsy from the edge of a recent bullous lesion. C4d immunostaining was performed and correlated with clinicopathology. Results:C4d immunohistochemistry was a reliable method for detecting AIBD in 29 of 30 cases diagnosed by histopathology, with 96.7% sensitivity. Also it was efficient in ruling out all the 5 negative cases ruled out by histopathology with 100% specificity. Conclusion: When correlated with the light microscopic and clinical findings, the C4d assay defines an important diagnostic adjunct in the evaluation of some autoimmune vesiculobullous dermatoses. It may prompt further DIF testing or, in some instances, may even define a reasonable substitute for DIF and/or add to the morphologic assessment of a biopsy specimen submitted for routine light microscopic assessment.