HPS1 and Hermansky-Pudlak syndrome: These studies added to the body of literature on AT2 cell apoptosis that loss of HPS-1 protein results in impaired autophagy, which contributes to lamellar body degeneration and AT2 epithelial apoptosis, and defective autophagy might therefore play a critical role in the initiation and development of HPS-PF (Figure 3).