FIGURE 1.

Cartoon overview of disorders of surfactant dysfunction. The lower airway and alveolus are represented. Type I and type II alveolar cells line the airway. Type II cells contain lamellar bodies that are responsible for generating surfactant. Normal type II alveolar cells have a circumferential organized appearance. SFTPC mutations cause milder surfactant dysfunction and may have normal or disorganized lamellar bodies. ABCA3 and NKX2–1 mutations can also have a range of severity of surfactant dysfunction and both have small disorganized lamellar bodies. Of note, neuroendocrine hyperplasia of infancy has also been reported in association with NKX2–1 mutations, which affects the lower airways rather than the alveolus. Mutations in SFTPB cause the most severe surfactant dysfunction, often lethal in the newborn period, and lamellar bodies are often decreased or absent. Mutations causing pulmonary alveolar proteinosis have normal lamellar bodies and normal surfactant secretions, rather, antibodies are generated to disrupt mechanisms of surfactant homeostasis. GM-CSF, granulocyte-macrophage colony-stimulating factor; PAS, periodic acid-Schiff