Bullous Pemphigoid as a Manifestation of Graft-Versus-Host Disease Following Allogeneic Hematopoietic Stem Cell Transplantation: A Systematic Review and Report of a Novel Case.

Background/Objective: Bullous Pemphigoid (BP) is a well-recognized autoimmune subepidermal blistering disease. However, its occurrence following allogeneic hematopoietic stem cell transplantation (HSCT) is extremely rare. The objective of this study is to systematically review the available data on BP following an allogeneic HSCT with focus on treatment options. Methods: A systematic review of studies evaluating BP following allogeneic HSCT, incorporating a highly treatment-resistant case from our graft-versus-host disease (GvHD) dermatology clinic, of a 47-year-old patient, notable as the only reported instance of BP following HSCT in a patient with chronic lymphocytic leukemia (CLL) that transformed into diffuse large B-cell lymphoma (DLBCL) and GvHD due to HSCT. The review yielded 15 publications that met the eligibility criteria. Including our case, a total of 16 cases were analyzed. Results: Nearly all patients (14/16) in this review had chronic GvHD due to their HSCT. Twelve patients were males, and six were of Japanese origin. The mean age for BP diagnosis was 38 years (a range of 5-67). On average, BP developed one year post-HSCT. The most common treatment for BP in these patients was prednisolone, with the majority experiencing complete resolution of symptoms. Conclusions: BP following HSCT is an exceptionally rare condition with an unclear underlying mechanism.