Incidence of P200 pemphigoid: A nationwide study

Overview & Synopsis

Abstract Background Anti‐p200 pemphigoid (P200) is a rare subepidermal autoimmune blistering disease (AIBD) related to anti‐laminin γ1 autoantibodies (Abs). It has been recently reported that laminin β4 was frequently recognized by sera from patients with P200. Objectives To evaluate the incidence of P200 in France using a new recombinant anti‐laminin β4 serological assay. Methods This multicentre retrospective study was conducted in the Immunology Laboratory of the French reference centre for AIBD from January 2018 to March 2023. Sera suspected of corresponding to P200 were tested using the new anti‐LAMB4 cell‐based immunoassay (CBIA) and/or immunoblotting (IB) on dermal extract. The incidence of P200 was then estimated based on its incidence rate relative to those of BP and pemphigus over the same period. Results 116 patients with sera labelling the dermal side of salt‐split skin by IIF and negative for other junctional AIBD were recorded. Among them, 23 patients' sera had already been tested positive for P200 by dermal IB. Thus, 93 patients' sera were tested with both the anti‐LAMB4 CBIA and IB: 85 were positive with the CBIA (91%) vs. 44 with IB (47%, p < 0.0001). Only two were positive with IB alone. Overall, 110 patients had anti‐p200 Abs. Subsequently, we compared the frequency of serological detection of P200 to that of BP and pemphigus based on data from centres that exhaustively submitted their sera to our reference laboratory. According to the incidence of BP and pemphigus in France (21.7 and 1.85 cases per million inhabitants per year, respectively), the incidence of P200 was estimated to range from 0.23 to 0.83 cases per million inhabitants per year. This corresponds to approximately 16–57 new cases annually in France, which is approximately 2‐ to 4‐fold more frequent than epidermolysis bullosa acquisita . Conclusions This study shows that P200 may be much more frequent than initially estimated.