HPS3 is involved in early stages of melanosome biogenesis and maturation. Defects in HPS3 are the cause of the cocoa (coa) mutant, and of Hermansky-Pudlak syndrome type 3 (HPS3). HPS3 is an autosomal recessive disorder, characterized by oculocutaneous albinism, bleeding due to platelet storage pool deficiency, and lysosomal storage defects. This syndrome results from defects of diverse cytoplasmic organelles including melanosomes, platelet dense granules and lysosomes. Ceroid storage in the lungs is associated with pulmonary fibrosis, a common cause of premature death in individuals with HPS.