What is the difference between giant cell (temporal) arteritis and Takayasu arteritis?

Both disorders affect large vessels. Takayasu’s arteritis manifests with a progressive granulomatous inflammation of the aorta and its major branches and most frequently afflicts patients aged ,50 years. Giant cell arteritis usually affects patients .50 years old with a granulomatous vasculitis that can also involve the aorta and its major branches. However, giant cell arteritis shows a predilection for the extracranial branches of the carotid artery, particularly the temporal artery, which can progress to visual loss and blindness if not treated with systemic steroids. Patients with giant cell arteritis may occasionally demonstrate unilateral alopecia, cutaneous ulceration or atrophy of the scalp due to loss of the blood supply to the skin.

Nordborg C, Nordborg E, Petursdottir V: Giant cell arteritis. Epidemiology, etiology, and pathogenesis, APMIS 108:713–724, 2000.