COL18A1 and Hermansky-Pudlak syndrome: Upon the examination of anti-lymphangiogenic growth factors, HPS and PRP were found to contain disproportional amounts of the investigated biomolecules, which makes the total lymphangiogenic effect difficult to predict: TSP-1 was comparable between HPS and PRP, but PF-4 was (as expected) 3.0× higher in PRP than in HPS, and endostatin was 7.5× higher in HPS than in PRP (Figure 1B).