Management of CMV Pneumonia, DAH, and BOS Following HSCT in a Child with β-Thalassemia: A Case Report.

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curative treatment for thalassemia major but carries a high risk of post-transplant complications. We report a pediatric case with β-thalassemia major who developed steroid-refractory grade III acute graft-versus-host disease (aGVHD) after HLA-9/10 mismatched unrelated donor allo-HSCT. This was followed by cytomegalovirus (CMV) reactivation that progressed to severe CMV pneumonia complicated by diffuse alveolar hemorrhage (DAH). Notably, after failure of first-line antiviral therapy, a combination of ganciclovir and letermovir was employed, resulting in complete virologic clearance and marked respiratory improvement. During follow-up, bronchiolitis obliterans syndrome (BOS) was diagnosed on day +154. The patient received repeated infusions of umbilical cord-derived mesenchymal stromal cells (UC-MSCs), initially for refractory intestinal aGVHD and later in conjunction with the FAM regimen (fluticasone, azithromycin, montelukast) for BOS, ultimately achieving full clinical recovery. This case highlights two key management insights: (1) the ganciclovir-letermovir combination can be effective in pediatric refractory CMV pneumonia, and (2) sequential UC-MSC administration may contribute to controlling both acute GVHD and late pulmonary complications. Finally, multidisciplinary collaboration and individualized strategies are essential in managing such complex post-transplant pulmonary syndromes in children.