To identify the pulmonary angiogenesis in HPS, we used immunofluorescence staining with CD31 in the lungs and found that the architecture of the lung vessel exhibited a progressing chaotically disorganized network, characterized by a distorted scattered lumpy area after CBDL (Fig. 1B), and more microvessel density in CBDL at 2 and 3 weeks than in sham rats (Fig. 1D). Here, PECAM1 is linked to Hermansky-Pudlak syndrome.