Pulmonary alveolar proteinosis in Denmark: a retrospective cohort study.

Background: Pulmonary Alveolar Proteinosis (PAP) is a rare respiratory disease characterized by proteinaceous material accumulation in the lungs, impairing gas exchange. The clinical course of the disease varies among patients. No current studies describe the Danish patient population. In 2024, the European Respiratory Society issued a guideline for the diagnosis and management of PAP. This study aimed to describe the demographical, clinical, laboratory, and radiological features of the Danish cohort of patients with PAP. Methods: All patient followed at Department of Respiratory Diseases and Allergy at Aarhus University Hospital (AUH) in the period from 2006 to 2023 were invited to participate. Data were collected retrospectively through hospital records. Results: Of 18 patients, 16 could be identified and agreed to participate in the study. The median age at diagnosis was 49.5 years and 62.5% of patients were male. Half the patients were referred from the Central Denmark Region. All patients presented with dyspnea at diagnosis with a median duration of symptoms of 11.7 months. A smoking history was present in 62.5%. Most diagnoses were made on the combined findings from high-resolution CT (HRCT), bronchoalveolar lavage (BAL) cytology and lung histology. Autoimmune PAP was diagnosed in 92.9%. Patients needing treatment received whole-lung lavage (WLL) or inhaled GM-CSF therapy as first-line therapy. Conclusion: The first Danish cohort of patients with PAP revealed characteristics similar to international cohorts. Treatment strategies aligned with the 2024 guidelines, while diagnostic biopsies were frequently taken during BAL reflecting the historical practice prior to the introduction of the guidelines.