Pulmonary alveolar proteinosis (PAP) is an uncommon cause of respiratory failure characterized by abnormal accumulations of surfactant proteins within alveolar spaces. 1 PAP can be due to an autoimmune process or secondary to various systemic diseases including hematopoietic disorders, immune dysregulation, infections, inhalations, lysinuric protein intolerance, iatrogenic, or secondary to drugs. 2 Autoimmune PAP represents 90% to 95% of adult cases of PAP but is more rare in pediatrics, accounting for 5% to 10% of all cases. 2 In this article, we present a case of PAP in the pediatric setting, with serology confirming a primary autoimmune process. A 13-year-old female patient presented with a 6-month history of progressive dyspnea on exertion. On admission, she was found to be hypoxemic, requiring oxygen therapy. Chest computed tomography scan revealed diffuse groundglass opacities accompanied by inter-and intra-lobular septal thickening, a pattern classically described as "crazy paving." She proceeded to whole lung lavage requiring extracorporeal membrane oxygenation (ECMO) for both diagnostic and therapeutic indications. Microscopy demonstrated dense eosinophilic, amorphous globules (Figure 1A), which were periodic acid-Schiff-positive and diastase resistant (Figure 1B), in a background of acellular debris and scant inflammatory cells. Electron microscopy showed these globules to have concentric lamellations characteristic of surfactant bodies (Figure 1C). These pathologic findings were consistent with the clinical suspicion of PAP. 3,4 Further serologic testing demonstrated anti-granulocyte-macrophage colony-stimulating factor (GM-CSF) antibodies, in keeping with autoimmune PAP. Her respiratory status significantly improved following the lavage. She was decannulated from ECMO and successfully extubated. She was discharged home with daily GM-CSF inhalations and nocturnal, supplemental oxygen with outpatient follow-up.