Utility of IgG4 immunohistochemistry detection in pemphigus diagnosis

Pemphigus includes a group of blistering autoimmune diseases that affect the skin and mucosa, characterized by the formation of epidermal bullous and the presence of antibodies against binding proteins. Pemphigus is classified according to clinical presentation, target molecule, and IgG production as pemphigus vulgaris, foliaceous, IgA-pemphigus, and paraneoplastic pemphigus. Thus, the identification of autoantibodies class and site of deposition is mandatory. The gold standard to identify the immune complex deposition is the direct immunofluorescences technique, performed in fresh tissue; unfortunately, this method is unavailable in the regional hospital at the Mexican provinces. Nevertheless, IgG subclass-4 is the prevalence of immunoglobulin in acantholysis. Therefore, this IgG subclass could be detected using IgG4 immunohistochemistry. Because direct immunofluorescences technique is absent in provinces or patients denied a new biopsy to confirm the diagnosis, this work presented pemphigus vulgaris confirmation using the IgG4 immunohistochemistry technique in patients with clinical lesions suggestive of pemphigus vulgaris and intraepidermal blister manifestation in histopathology.