A case of severe oral mucosal GVHD induced by heterologous SARS-CoV-2 vaccination after cord blood transplantation.

Patients who have undergone hematopoietic cell transplantation (HCT) are at a higher risk of severe acute respiratory syndrome coronavirus 2 (SARS-Cov-2) infection than the general population. Therefore, early vaccination is recommended for post-transplant patients. Although exacerbation of chronic graft-versus-host disease (cGVHD) after the initial vaccination has been reported, it is unknown whether severe cGVHD occurs when different RNA vaccines are combined. We treated a patient who developed severe oral mucosal cGVHD after receiving two different RNA vaccines. Visual inspection showed that the patient presented with typical mucocutaneous cGVHD, and cGVHD in this case responded well to low-dose steroids compared to common oral GVHD exacerbations. Histopathological findings revealed T cell, B cell, and conspicuous neutrophil infiltration. Multiple doses of SARS-Cov2 vaccination are required in post-transplant recipients. In conclusion, it is essential to obtain the vaccination history of allo-HSCT recipients with cGVHD exacerbation. Furthermore, reviewing the pathological findings may help treat patients with lower doses of steroids.