Pleuroparenchymal Fibroelastosis Complicated by Pulmonary Alveolar Proteinosis After Peripheral Blood Stem Cell Transplantation

A 52-year-old man with a history of Philadelphia chromosome-positive acute lymphoblastic leukaemia underwent peripheral blood stem cell transplantation (PBSCT) 10 years earlier. Five years after transplantation, he developed a persistent dry cough and exertional dyspnea. High-resolution CT revealed upper lobe-predominant subpleural fibrosis compatible with pleuroparenchymal fibroelastosis (PPFE) and lower lobe reticulation with ground-glass opacities. Video-assisted thoracoscopic lung biopsy showed subpleural fibroelastosis and bronchocentric lesions, along with intra-alveolar accumulation of foamy macrophages containing cholesterol crystals and periodic acid-Schiff-positive material, with surfactant protein A immunoreactivity-consistent with pulmonary alveolar proteinosis (PAP). Despite corticosteroids, tacrolimus, and subsequent antifibrotic therapy with nintedanib, the disease gradually progressed, and the patient ultimately died of acute exacerbation triggered by SARS-CoV-2 infection. This case highlights a rare coexistence of PPFE and PAP after PBSCT and underscores the potential role of chronic graft-versus-host disease and immune dysregulation in their pathogenesis.