The ankle-brachial index (ABI; the ratio of systolic blood pressure in the ankle to that in the arm), is a measure of occlusion of peripheral arteries in the leg. Peripheral arterial stenosis may be observed with atherosclerosis and with increased intima media thickness as seen in diseases such as pseudoxanthoma elasticum. The most common cause of peripheral arterial stenosis in patients over 40 years of age is atherosclerosis. Cerebral and coronary arteries are by definition not included in peripheral artery disease.