Bronchiolitis Obliterans Syndrome Following High-Dose Chemotherapy and Autologous Hematopoietic Stem Cell Transplantation in a Pediatric Patient With Neuroblastoma.

Bronchiolitis obliterans syndrome (BOS) is a chronic obstructive pulmonary disorder most often recognized as a pulmonary manifestation of chronic graft-versus-host disease after allogeneic hematopoietic stem cell transplantation (HSCT). Its occurrence following autologous HSCT (auto-HSCT) is exceedingly rare, and its clinical features and prognosis remain poorly defined. We report the case of a five-year-old girl with neuroblastoma who developed BOS after high-dose chemotherapy with thiotepa and melphalan followed by auto-HSCT. Respiratory symptoms, including dyspnea, wheeze, and oxygen desaturation, emerged almost simultaneously with hematopoietic engraftment. Computed tomography demonstrated mosaic attenuation with air trapping, and pulmonary function tests revealed peripheral airway obstruction, while infectious evaluations were entirely negative. Despite initial treatment with bronchodilators and corticosteroids, symptoms persisted beyond six weeks, leading to a diagnosis of BOS. Multimodal therapy, including methylprednisolone pulse therapy, intravenous immunoglobulin, inhaled corticosteroids, and azithromycin, resulted in the resolution of clinical symptoms and discontinuation of oxygen supplementation, although radiographic abnormalities remained. This case suggests that, although BOS is generally considered irreversible after allo-HSCT, BOS following auto-HSCT in children may follow a more reversible course, underscoring the importance of timely diagnosis and therapeutic intervention, and supporting the concept that the underlying mechanisms of BOS may differ between allo- and auto-HSCT.