Secondary pulmonary alveolar proteinosis associated with aluminum exposure: a case report and literature review

Pulmonary alveolar proteinosis (PAP) is a rare disorder characterized by abnormal accumulation of surfactant-derived material within the alveoli. Occupational exposure-related secondary PAP is uncommon, and aluminum dust represents one of the recognized metallic exposures associated with this condition, although reported cases remain limited. A 45-year-old man presented with progressive dyspnea, hypoxemic respiratory failure, and diffuse bilateral ground-glass opacities. Extensive infectious and autoimmune investigations were negative. Bronchoalveolar lavage fluid (BALF) appeared characteristically milky with abundant sediment. Histopathological and cytological examinations demonstrated intra-alveolar proteinaceous material with positive periodic acid-Schiff (PAS) and diastase-resistant PAS staining. Anti-granulocyte–macrophage colony-stimulating factor (GM-CSF) antibodies were negative (3.25 U/mL). Detailed occupational history revealed recent employment involving aluminum spraying and electric welding. Quantitative elemental analysis demonstrated markedly elevated aluminum concentrations in BALF (1473.6µg/L versus 103µg/L in healthy controls) and workplace welding residues (6011.8 µg/L). Sequential bilateral whole-lung lavage resulted in significant clinical and radiological improvement. This case demonstrates a comprehensive exposure–deposition evidence chain linking occupational aluminum-containing welding fumes, elevated aluminum concentrations in workplace residues and bronchoalveolar lavage fluid, and the development of secondary PAP. This case highlights that occupational aluminum exposure may present as secondary PAP rather than classical pneumoconiosis alone. Clinicians should maintain a high index of suspicion for occupational PAP in patients with unexplained diffuse pulmonary infiltrates and a relevant exposure history.