People frequently use their hands when telling a story. Your feet sometimes have a story to tell as well, revealing a medical problem that might otherwise go unrecognized. Cold, purple feet signal an abnormality with the arterial circulation, the part of the circulatory system that delivers oxygenated blood from the heart to the body organs and tissues. The venous circulation, which carries oxygen-depleted blood back to the heart, is also involved in some conditions that cause cold, purple feet. Peripheral artery disease is the most common culprit for these symptoms. Other uncommon conditions are sometimes responsible.
Foot Color and Temperature With Arterial Disease
Like all body organs and tissues, the feet require a constant supply of oxygenated, arterial blood. Insufficient arterial blood flow -- known medically as ischemia -- causes predictable signs and symptoms in the feet. The temperature of the skin primarily depends on blood flow through the skin and underlying tissue. Unexplained coolness of the foot is characteristic of arterial ischemia, which usually develops gradually over many years but can also have a sudden onset.
Depending on the position of the foot and the cause of the ischemia, red, white and blue or purple skin discoloration is also typical of arterial disease affecting the feet. White discoloration of the skin, or pallor, occurs when arterial blood flow to the foot is critically low or completely blocked. If the blood flow does not improve quickly, the foot skin may turn bluish as the oxygen level in the foot tissue drops. If blood flow subsequently improves -- due to opening of the obstructed arteries or positioning the foot below the heart -- the affected skin turns purplish-red as blood rushes back into the foot and all blood vessels maximally dilate in a renewed attempt to enrich the tissues with oxygen.
Most Common Cause of Foot Ischemia
Peripheral artery disease (PAD) refers to narrowing of arteries that carry oxygenated blood to various parts of the body. This condition affects an estimated 8.5 million Americans aged 40 or older, according to 2016 data from the American Heart Association. PAD most commonly affects the feet and legs and is the most common cause of foot ischemia. The overwhelming majority of PAD cases are due to atherosclerosis, the development and growth of cholesterol-rich deposits within the arteries that obstruct blood flow.
Cigarette smoking and diabetes are the major risk factors for PAD, along with high blood pressure and elevated blood cholesterol. Like other forms of atherosclerosis, PAD affecting the feet and legs typically causes no symptoms for many years. Coolness of the feet and purplish discoloration of the skin -- especially while standing or sitting -- may be among the first noticeable symptoms. Symptomatic PAD typically affects seniors, especially those older than age 60.
Other Causes of Foot Ischemia
Although PAD is the culprit in the overwhelming majority of people, there are other uncommon conditions that can also cause cold, purple feet. Buerger disease, also known as thromboangiitis obliterans, is an inflammatory condition that affects small- to medium-sized arteries. Similar sized veins are sometimes involved as well. Inflammation of the involved blood vessels triggers formation of clots that obstruct blood flow in the affected area. The lower legs and feet are most commonly involved with Buerger disease. When the condition causes reduced arterial blood flow to the foot, symptoms similar to that of PAD develop, including cool skin temperature and skin discoloration. Cigarette smoking is the leading risk factor for Buerger disease, which primarily affects young and middle-aged men.
Acrocyanosis is another uncommon condition characterized by abnormal regulation of blood vessels. This leads to inappropriate constriction of the involved small arteries and dilation of the small veins, resulting in cool skin that appears bluish or purple. The feet and hands are most commonly affected. The involved skin may also appear doughy, due to local swelling. The cause of acrocyanosis remains unknown. Young to middle-aged women are primarily affected and symptoms tend to decrease with age -- in sharp contrast to PAD.
Other PAD Symptoms and Possible Complications
Because PAD comes on gradually, the symptoms are often overlooked until the disease is advanced. In addition to cold, purple feet, possible symptoms of lower extremity PAD may include:
-- muscle pain or cramps in the legs or feet while walking, and relieved with rest
-- persistent leg or foot pain in people with advanced PAD
-- numbness, tingling or burning of the feet
-- loss of hair on the lower legs and feet
-- thin, fragile skin on the lower legs and feet
People with advanced PAD are vulnerable to skin ulcers on the lower legs and feet. Due to ongoing tissue ischemia, these ulcers often persist or heal very slowly. Scrupulous, professional wound care is needed to avoid serious infection or the development of gangrene, which refers to the death of a localized area of tissue. Gangrene is a serious complication of PAD that often necessitates amputation of the diseased tissue of the foot or leg.
Warnings and Precautions
See your doctor as soon as possible if you notice that one or both of your feet are often cold and/or purple. Like atherosclerosis involving the blood vessels of the heart, PAD of the lower extremities is a treatable condition -- and the sooner, the better. If you have symptoms suggestive of PAD or diabetes, seek urgent medical care if you develop a sore or ulcer on one or both of your feet, or on your toes.
Seek immediate medical care if one of your feet suddenly becomes very pale or blue and cold -- and remains so even when you are sitting or standing. This could indicate complete blockage of arterial blood flow to the affected foot. Emergency medical care is needed in this situation to save the foot.
- Manual of Vascular Diseases; Sanjay Rajagopalan, et al.
- Circulation: Heart Disease and Stroke Statistics -- 2016 Update
- Merck Manual Professional Version: Thromboangiitis Obliterans (Buerger Disease)
- Professional Guide to Diseases, 9th Edition; Lippincott Williams & Wilkins
- Dermatology, 2nd Edition; Otto Braun-Falco, et al.
- Merck Manual Professional Version: Peripheral Arterial Disease (Peripheral Vascular Disease)