A primarily a lung disorder characterized by onset of respiratory insufficiency due to pulmonary alveolar proteinosis (PAP) in the first months of life. Affected individuals may have normal respiratory function at birth. Development of the disorder appears to be influenced or triggered by viral infection, manifest as progressive respiratory insufficiency, confluent consolidations on lung imaging, and diffuse collection of periodic acid-Schiff (PAS)-positive material in pulmonary alveoli associated with small and nonfoamy alveolar macrophages. Patients also have hypogammaglobulinemia, leukocytosis, and splenomegaly. Many patients die of respiratory failure in infancy or early childhood; hematopoietic stem cell transplantation (HSCT) is curative. The pathogenesis may be related to abnormal function of alveolar macrophages, resulting in decreased catabolism of surfactant. The disorder results from a gain-of-function effect that particularly affects B cells and monocytes. The disease is pulmonary alveolar proteinosis with hypogammaglobulinemia (MONDO_0020840). Also known as: PAPHG, immunodeficiency (due to OAS1 gain-of-function variant) with pulmonary alveolar proteinosis and hypogammaglobulinemia.