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.