Pulmonary fibrosis in patients with auto-immune pulmonary alveolar proteinosis: a retrospective nationwide cohort study

Autoimmune pulmonary alveolar proteinosis (aPAP) is a rare disease that may progress toward pulmonary fibrosis. Data about fibrosis prevalence and risk factors are lacking.In this retrospective multicentric nationwide cohort, we included patients newly diagnosed with aPAP between 2008 and 2018 in France and Belgium. Data were collected from medical record, using a standardized questionnaire.Sixty-one patients were included in the final analysis. We identified 5 patients (8%) with fibrosis on initial CT and 16 patients (26%) with fibrosis on final CT after a median time of 3.6 years. Dust exposure was associated with pulmonary fibrosis occurrence (OR=4.3; p=0.038).aPAP patients treated with whole lung lavage (WLL), rituximab, or GM-CSF therapy did not have more fibrotic evolution than patients who did not receive these treatments (n=25/45, 57%versusn=10/16, 62%, p=0.69). All-cause mortality was significantly higher in fibrotic than in non-fibrotic cases: n=4/16, 25%versusn=2/45, 4.4%, p=0.036 respectively.In our population, a quarter of aPAP patients progressed toward pulmonary fibrosis. Dust exposure seems to be an important factor associated with this complication. More studies are needed to analyse precisely the impact of dust exposure impact, especially silica, in patients with aPAP.