The application of direct immunofluorescence in the pathological diagnosis of oral mucosal diseases: Series of 116 cases.

This study evaluated the diagnostic utility of direct immunofluorescence (DIF) in 116 oral mucosal bullous and atrophic lesions from Zhejiang University Stomatology Hospital (2022-2024). DIF and H&E analyses were performed on serial sections of the same biopsy specimens. Among the cases, 45 were diagnosed with pemphigus vulgaris, in which DIF revealed a reticular pattern of IgG (84.44 %) and C3 (73.33 %) deposition within the epithelial prickle cell layer. Benign mucous membrane pemphigoid was identified in 23 cases, characterized by linear deposits of IgG (56.52 %) and C3 (73.91 %) along the basement membrane zone (BMZ), with occasional expression of IgA (34.78 %) and IgM (17.39 %). In 14 cases of oral lichen planus, DIF demonstrated positive fibrinogen deposition in the BMZ (57.14 %), while IgA, IgG, IgM, and C3 were either weakly expressed or absent. 4 cases of chronic discoid lupus erythematosus exhibited granular deposits of IgG (100 %), sometimes accompanied by IgA, IgM, C3, and fibrinogen in the BMZ and perivascular. One case of linear IgA bullous dermatosis showed exclusive linear IgA deposition in the BMZ, with no detectable IgG, IgM, C3, or fibrinogen. DIF demonstrates significant clinical value in the diagnosis of atrophic and bullous lesions, particularly in pemphigus and lichen planus. The combination of IgG, C3 and fibrinogen may be economical and effective approach.