The natural history of Pulmonary Alveolar Proteinosis (PAP): data from the Italian National Reference Center

Background: PAP is a ultra-rare syndrome characterized by the accumulation of surfactant material within the alveolar spaces. The current therapy with whole lung lavage (WLL) is still the gold standard even if clinical trials with inhaled rGM-CSF supplementation are ongoing. Aims: To prospectively study the Italian PAP population. Methods: We carried out a descriptive study of the baseline characteristics of the PAP patients enrolled in the Italian registry from 1989 until 2019. Results: We enrolled 126 PAP, among these 92.8% were affected by autoimmune (aPAP), while the remaining patients were divided in: hereditary (0.8%), secondary (3.2%) and PAP-like (3.2%). Considering the aPAP patients, the mean age at diagnosis was 43±14, with a male/female ratio = 2. Smoking history was reported in 66.7% of cases; 37.2% of them are currently smokers. 49 patients did not necessitate WLL treatment in the long-term follow up. The baseline pulmonary function test (PFT) (% of predicted value) of aPAP patients is shown in tab. 1, as mean±SD. Differences are significant also in a multivariate regression analysis, taking into account age, sex and smoking habit. Conclusions: The establishment of a national registry for PAP has enabled a detailed characterization of the natural course of the disease, moreover our results indicate that also PFT could recommend on when to treat, along with persistent or progressive respiratory failure and exercise desaturation.