Causes

With giant cell arteritis, the lining of arteries becomes inflamed, causing them to swell. This swelling narrows your blood vessels, reducing the amount of blood — and, therefore, oxygen and vital nutrients — that reaches your body's tissues.

Almost any large or medium-sized artery can be affected, but swelling most often occurs in the arteries in the temples. These are just in front of your ears and continue up into your scalp.

What causes these arteries to become inflamed isn't known, but it's thought to involve abnormal attacks on artery walls by the immune system. Certain genes and environmental factors might increase your susceptibility to the condition.