B42-08 Heterogeneous Prognosis of Patients With Alveolar Macrophage Pneumonia

Introduction Alveolar macrophage pneumonia (AMP, formerly known as desquamative interstitial pneumonia) is a rare and poorly described form of diffuse interstitial pneumonia. Methods We conducted a retrospective multicenter study including all patients diagnosed with AMP during a multidisciplinary team meeting at one of the OrphaLung reference centers between 1999 and 2024. Results Among the 115 patients evaluated, 30 were excluded (alternative diagnosis, n = 20; absence of pulmonary function testing, n = 7; other reasons, n = 3). The main clinical characteristics of the 85 included patients are presented in Table 1. After diagnosis, 15 patients (18%) quit smoking, and pulmonary improvement was observed in four of them (27%). Twenty-nine patients (34%) received corticosteroids, with pulmonary improvement observed in eight cases (28%). Immunosuppressive therapy was prescribed for 13 patients (15%), and only one showed pulmonary improvement. Four patients (5%) were treated with azithromycin, with no respiratory improvement. Fifteen patients (18%) received antifibrotic therapy. After a median follow-up of 42 months (range 17-94 months), 37 patients (44%) showed functional decline. Four patients died, one underwent lung transplantation, and seven (8%) developed bronchopulmonary cancer. Conclusion The prognosis of patients with AMP is heterogeneous: fewer than one-third of the analyzed patients showed respiratory improvement after smoking cessation or corticosteroid therapy. Ongoing inclusions and analyses should help identify prognostic factors.