Figure 1.

Lysosome-related organelles (LROs) are a group of cell type–specific subcellular compartments that share some features with endosomes and lysosomes, but also develop unique properties as they harbor specialized cargoes. Many of the clinical manifestations of Hermansky–Pudlak syndrome (HPS) are explained by abnormalities in the formation and trafficking of LROs, including albinism (melanosomes), bleeding (platelet-dense granules), and pulmonary fibrosis (likely related at least in part to abnormal lamellar body genesis in type II alveolar epithelial cells).