PDE4D and Stroke: Epidemiological studies have identified several clinical risk factors that are highly correlated with stroke risk; these in turn implicate various biological pathways, including the homocysteine metabolism[3], lipid metabolism[4], renin-angiotensin-aldosterone system[5]–[6], haemostatic system[6], phosphodiesterase 4D[7] and leukotriene pathways[8], in stroke pathophysiology.