Giant cell arteritis.

Giant cell arteritis is a systemic vasculitis with a wide clinical spectrum, and it represents a medical emergency. Visual loss is the most feared complication, and when it happens, it tends to be profound and permanent. Prompt diagnosis and treatment are imperative to minimize potentially devastating visual loss and neurologic deficits. A temporal artery biopsy should be performed on every patient in whom the diagnosis is suspected. The mainstay of therapy remains corticosteroids.