B42-13 Pulmonary Alveolar Proteinosis: Characteristics From an ERN-lung National Referral Centre Cohort

Rationale Pulmonary alveolar proteinosis (PAP) is a rare lung syndrome characterised by impaired surfactant clearance by alveolar macrophages. The worldwide prevalence of PAP is estimated to be ∼7 per million. Diagnosis is likely underestimated due to non-specific clinical and radiographic features that mimic other common presentations of interstitial lung diseases. St Vincent’s University Hospital serves as a national referral centre for rare lung disease in Ireland. We describe the cohort of patients with PAP managed at our institution. Methods This is a single centre observational study looking at patients who attended a rare lung disease clinic with a diagnosis of PAP. Data analysed included age, gender, symptoms at presentation, treatment received and imaging features. We also explored methods of diagnosis and if patients underwent more than one diagnostic modality. Results We identified 15 patients attending our clinic with a diagnosis of PAP. 9 (60%) patients were male, with a mean age across the cohort of 58.9 years. The most common presenting symptom was dyspnoea (11/15; 73%) with cough also reported in 7 of these cases. Notably, 3 patients were diagnosed incidentally following abnormal chest imaging performed for unrelated indications. Mean DLCO at time of presentation was 65.3% (+/-16.5%).All patients had baseline CT imaging at diagnosis. Ground-glass opacities were documented in all cases, with a “crazy-paving” pattern described in only 40%. GM-CSF antibodies were positive in 12 patients. Bronchoalveolar lavage (BAL) was performed in 9 patients, all of which showed PAS-positive staining. 8 (53%) patients are currently prescribed statin therapy, including 4 patients who commenced treatment following their PAP diagnosis. 3 (20%) patients have previously undergone whole lung lavage. 2 patients are receiving inhaled GM-CSF therapy. Conclusions While the incidence of PAP is rare, it is an under recognised condition requiring specialist care in a centralised centre to streamline diagnosis and optimise treatment strategies. Our cohort is the largest single centre experience described in Ireland, highlighting the value of co-ordinated national referral pathways for rare lung diseases.