Diagnosis of autoimmune subepidermal bullous diseases with mucous membrane involvement based on laser-scanning confocal microscopy.

Background Mucosal involvement in autoimmune subepidermal blistering disorders (ASBD) may represent the only or predominant localization. Circulating autoantibodies are detected in 50% cases. Objectives The aim of this study was to evaluate the usefulness of fluorescence overlay antigen mapping by laser-scanning confocal microscopy method (FOAM-LSCM) to identify ASBD with mucosal involvement in oral mucosa specimens. Materials and methods Thirty-two ASBD patients, diagnosed based on direct immunofluorescence between 2006 and 2016, were enrolled. Localization of IgG deposits bound at the basement membrane zone, relative to laminin-332 and collagen IV localization, was assessed in vivo. Results FOAM-LSCM disclosed four different immunofluorescence patterns. IgG deposits were located above laminin-332, as in bullous pemphigoid (BP-type), in 19% cases and co-localized with laminin-332 (anti-laminin-332-type) in 6% cases. IgG deposits were found below laminin-332 and above collagen IV (mucous membrane pemphigoid-type) in 59% cases, and below collagen IV (epidermolysis bullosa acquisita-type) in 16%. Circulating antibodies were found in 56% cases. Conclusion The FOAM-LSCM method should be used in order to obtain a definitive diagnosis of ASBD with mucosal involvement, particularly in the presence of negative circulating antibodies.