A83-03 Emerging Environmental Triggers in Alveolar Macrophage Pneumonia: A Never-smoker Exposed to Construction Dust

Introduction

Alveolar Macrophage Pneumonia (AMP), newly designated in the 2025 International Multidisciplinary Classification of the Idiopathic Interstitial Pneumonias by the ERS/ATS and previously termed Desquamative Interstitial Pneumonia (DIP), represents a rare interstitial pneumonia characterized by diffuse intra-alveolar macrophage accumulation with interstitial inflammation. (1) Classically associated with tobacco smoke and occupational inhalational exposures, AMP may also arise in the absence of recognized risk factors, emphasizing the importance of clinical vigilance when evaluating chronic respiratory symptoms. (1) This case describes a healthy young adult with no smoking history who developed AMP, expanding the clinical understanding of environmental triggers beyond traditionally described exposures.

Case Presentation

A 38-year-old male without significant past medical history presented with a one-year history of progressive cough and exertional dyspnea, subsequently complicated by nocturnal fevers and two episodes of hemoptysis. He denied smoking, recent travel, or infectious contacts; however, he reported frequent dust exposure while working in construction over the preceding year.Chest radiography revealed progressive perihilar and bilateral lower-lobe opacities compared with imaging from one year prior. High-resolution computed tomography demonstrated patchy and confluent ground-glass opacities predominantly in the lower lobes with extension to the upper lobes. (Figure 1.A) Differential diagnosis included atypical pneumonia and malignancy. Comprehensive infectious testing was negative. Bronchoscopy with bronchoalveolar lavage and transbronchial cryobiopsy showed abundant intra-alveolar macrophages without malignant cells or granulomas, consistent with AMP. (Figure 1.B) The patient initiated systemic corticosteroid therapy and demonstrated clinical improvement.

Discussion

AMP is a rare macrophage-predominant interstitial pneumonia typically linked to inhalational toxicants, most commonly tobacco smoke. Clinical manifestations include chronic cough and exertional dyspnea. Radiographic features typically demonstrate diffuse ground-glass opacities with basal predominance, while histopathology reveals pigmented macrophages filling alveolar spaces. Management focuses on the elimination of the offending exposure and systemic corticosteroids, although disease progression despite treatment has been reported.This case is notable due to the absence of smoking and the probable association with nonspecific construction-related dust exposure. Although inorganic dust-related AMP has been described, it is classically associated with complex particulate exposures (such as beryllium, silica, and asbestos) and occupations, including farming, metalworking, and textile manufacturing, rather than general construction settings. (2, 3) This case highlights that seemingly benign particulate exposure may precipitate AMP and emphasizes the need for thorough occupational assessment in patients with unexplained interstitial lung disease. Continued recognition of atypical presentations will refine the evolving understanding of AMP and inform timely diagnosis and treatment.

This abstract is funded by: None