A3-01 Airway-predominant Fibroelastosis Twelve Years After an Allogeneic Bone Marrow Transplant

Introduction

Pleuroparenchymal fibroelastosis (PPFE) is a rare pulmonary disease occurring idiopathically or following hematopoietic stem cell transplantation (HSCT) as part of the spectrum of chronic graft versus host disease (GVHD). Classic PPFE causes restrictive physiology with upper-lobe pleural and subpleural fibrosis (1,2). However, post-HSCT patients may develop atypical, airway-predominant fibroelastosis with obstructive or mixed physiology, a variant sometimes described as alveolar fibroelastosis (AFE) that can mimic bronchiolitis obliterans syndrome (BOS) (3).

Case Description

A 27-year-old woman with a history of allogeneic bone marrow transplant at age 15 (October 2012) for aplastic anemia with a 5q- deletion, subsequently developed post-transplant complications including acute cutaneous GVHD, ovarian failure, proteinuria, and hypertension. Years later, she developed recurrent respiratory infections, including Mycobacterium avium complex (MAC) disease, completing antibiotic therapy in May 2024 with microbiologic clearance. Despite clearance, her dyspnea and pulmonary function continued to decline. She was hospitalized for worsening dyspnea; CT imaging in July and August 2024 demonstrated upper-lobe-predominant ground glass opacities and lower-lobe-predominant bronchiectasis. PFTs declined dramatically from FEV1 of 1.57 (57%) and DLCO 14.88 (64%) in 2022 to FEV1 0.94 (26%) and DLCO 9.82 (42%) in 2024. Suspecting BOS, she underwent a right middle and lower lobe wedge biopsy in December 2024. Histology revealed minimal pleural thickening and bronchiolocentric fibroelastosis with no evidence of BOS (Figure 1).

Discussion

This case illustrates a critical diagnostic challenge in post-HSCT lung disease: distinguishing airway-predominant fibroelastosis from BOS. The distinction carries major prognostic and therapeutic implications, as fibroelastotic disease is typically refractory to immunosuppression. Classic PPFE presents with restrictive physiology and pleural-predominant disease (1,2). However, as described by Jonigk et al., post-transplant patients may develop airway-centric AFE with obstructive or mixed physiology (3). Our patient’s progressive airflow limitation, bronchiolocentric fibrosis, and minimal pleural involvement align with this AFE variant. The terminology “alveolar fibroelastosis” is not yet standardized, and overlap with other fibrotic and airway-centered processes, including pleural-dominant PPFE and bronchiolitis obliterans, remains common. Histologically, AFE demonstrates dense peribronchiolar fibroelastosis with preserved small-airway lumina, whereas BOS shows concentric bronchiolar obliteration. AFE generally portends progressive fibrotic decline requiring lung transplantation, while BOS may partially respond to immunomodulation. Recognition is essential because AFE clinically mimics BOS, potentially leading to delayed transplant referral or inappropriate immunosuppression escalation. This case emphasizes that post-HSCT fibroelastosis exists along a pleural-to-bronchiolar continuum, and surgical lung biopsy may be required when clinical and radiographic features are atypical.

This abstract is funded by: None