The current findings that a proportion of pulmonary EC express FVIII and vWF on the cell surface, together with recent evidence that resting EC can constitutively express membrane constituents involved in sustained FVIII/IXa-dependent activation of FX [42], lead us to hypothesise that dysregulated pulmonary endothelial FVIII processing may contribute to exuberant local intravascular thrombus formation in these pulmonary hypertension phenotypes. Here, VWF is linked to pulmonary arterial hypertension.