Flow cytometry helps differentiate between mucous membrane pemphigoid and erosive oral lichen planus.

This cross-sectional study investigated the immunophenotype of patients with mucous membrane pemphigoid (MMP) and erosive oral lichen planus (eOLP) evaluating flow cytometry as additional method in differential diagnosis. Thirty patients (18 MMP and 12 eOLP) were recruited. A blood sample was collected from each patient and B and T lymphocytes subsets were characterized through flow cytometry. Disease severity was additionally scored and MMP patients were characterized as high or low-risk based on the extent of mucosal involvement. Any correlation was finally investigated between the immunophenotype and clinical and serological data. High-risk MMP reported higher frequencies of memory cytotoxic T cells (P < 0.01**), memory helper T cells (P < 0.001***), pre-switch and post-switch memory B cells (P < 0.01**) and lower frequencies of naïve cytotoxic T cells (P < 0.01**), naïve helper T cells (P < 0.001***) and naïve B cells (P < 0.05*) compared to low-risk MMP. Additionally, a significant lower frequency of Th1 cells (P < 0.05*) and memory cytotoxic T cells (P < 0.001***) was found in MMP compared to eOLP and both the biomarkers reported high diagnostic accuracy with an AU-ROC value of 0.76 (P < 0.05*) and 0.86 (P < 0.001***), respectively. No differences between the two diseases were reported in B-cell repertoire. T-cell immunophenotyping mirrors the different pathophysiology of MMP and eOLP and could provide a better understanding of the role of cellular immunity in MMP. MMP and eOLP can share similar clinical manifestations and can be challenging to distinguish through the histological and serological tests currently available. Flowcytometric assessment of T-cell subsets could be potentially useful in differentiating between the two diseases.