Successful treatment of steroid-dependent gastrointestinal acute graft-versus-host disease with mesenchymal stromal cells administered more than 100 days after allo-HCT.

Administration of mesenchymal stromal cells (MSCs) represents a promising therapy for steroid-resistant acute graft-versus-host disease (aGVHD). However, its efficacy in pediatric patients with steroid-dependent aGVHD remains unclear, given the paucity of studies performed in children. In addition, the duration between the onset of aGVHD and MSC therapy is reportedly critical; a delay in MSC administration negatively impacts overall survival and response rate. Herein, we describe a case of a 14-year-old girl with steroid-dependent aGVHD who was successfully treated with MSCs following a prolonged duration from aGVHD diagnosis. The patient was diagnosed with T-cell lymphoblastic leukemia with central nervous system involvement and underwent cord blood transplantation (CBT). She developed severe gastrointestinal aGVHD on day +14 after CBT and was treated with a steroid; however, her aGVHD was repeatedly exacerbated upon tapering the steroid, later complicated by diabetic ketoacidosis. We eventually implemented MSC therapy for steroid-dependent aGVHD on day +109 after CBT. She rapidly responded to therapy, and her aGVHD was ameliorated even with steroid tapering. This case exemplifies the potential role of MSCs in treating pediatric patients with steroid-dependent aGVHD or late aGVHD.