SESSION TITLE: Tuesday Medical Student/Resident Case Report Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: 10/22/2019 01:00 PM - 02:00 PM INTRODUCTION: Differential diagnosis of bilateral diffuse pulmonary infiltrate is broad and includes both infectious and noninfectious etiologies, such as vasculitis, allergic bronchopulmonary aspergillosis, interstitial lung disease and autoimmune disease. CASE PRESENTATION: A 45 year old male with a presumptive diagnosis of hypersensitivity pneumonitis presented with worsening shortness of breath and was admitted to the hospital. He received steroids and 5 day course of levofloxacin, but remained hypoxic requiring up to 10 liter oxygen. Due to his worsening respiratory status, he was transferred to the intensive care unit (ICU). On admission to the ICU, chest radiograph showed progressing patchy airspace disease diffusely throughout both lungs. CT chest revealed nonspecific diffuse and patchy ground glass opacity with interlobular septal thickening and superimposed consolidative opacities throughout both lungs, in a crazy paving pattern. He continued treatment with intravenous steroids but had minimal improvement in his respiratory status. He underwent bronchoscopy with bronchoalveolar lavage (BAL) on day 5, which showed scant thick secretions with occasional streak of blood. Based on his imaging results and bronchoscopy appearance, the top differential for his acute on chronic respiratory failure was pulmonary alveolar proteinosis (PAP). He subsequently underwent bilateral total lung lavage during which large amount of debris was cleared from both lungs, and periodic acid-Schiff (PAS) stain showed clumps of granular acellular material suggestive of intra-alveolar proteinosis. Culture from BAL also showed polymicrobial growth with streptococcus anginosus and rothia dentocariosa, and he completed 7 day course of antibiotic therapy, initially with cefepime and then transitioned to ceftriaxone. By the time of discharge, his oxygen requirement was 3L/min via nasal cannula and he was started on GM CSF. DISCUSSION: PAP is a rare disease characterized by accumulation of PAS-positive lipoproteinaceous material in the distal air spaces due to impaired surfactant clearance. Auto-immune PAP is the most common etiology with estimated prevalence of 4 to 40 cases per million. CT scan is the major tool in diagnosis of PAP with patterns of ground-glass opacities, septal reticulations and parenchymal consolidation being highly suggestive of the disease. Diagnosis requires BAL which reveals milky fluid and positive PAS-staining granules. The mainstay of treatment remains symptomatic total lung lavage with GM CSF as an adjunct. CONCLUSIONS: In patients with acute on chronic respiratory failure, the appearance of diffuse ground-glass opacities, septal reticulations and parenchymal consolidation should raise concern for PAP. Proper diagnostic workup includes BAL with PAS staining. Reference #1: Singh I, Kaner R. A Woman with Asthma and Ground-Glass Opacities. Ann Am Thorac Soc. 2017;14(1):140-144. Reference #2: Rosen SH, Castleman B, Liebow AA. Pulmonary alveolar proteinosis. N Engl J Med. 1958;258(23):1123-42. Reference #3: Borie R, Danel C, Debray MP, et al. Pulmonary alveolar proteinosis. Eur Respir Rev. 2011;20(120):98-107. DISCLOSURES: No relevant relationships by Alice Gallo De Moraes, source=Web Response No relevant relationships by Melissa Myers, source=Web Response No relevant relationships by Zhenmei Zhang, source=Web Response