Giant cell arteritis (GCA) is a systemic vasculitis affecting medium- to large-sized arteries, including the aorta and the extracranial branches of the carotid artery. GCA is rarely found in individuals younger than 55, and the mean age for disease presentation is 76.

Patients may present with systemic symptoms such as a new temporal headache, fever, anorexia, weight loss, morning stiffness in the shoulder or neck, myalgia, fatigue, and anemia. There may be elevated ESR or C-reactive protein, temporal artery tenderness to palpation, or decreased arterial pulsation unrelated to arteriosclerosis. Patients may have scalp tenderness, visual disturbances (amaurosis fugax), jaw or tongue claudication or difficulty chewing, or upper cranial palsies.

GCA and polymyalgia rheumatica (PMR) have a significant clinical association: 16%-21% of cases of PMR are associated with GCA, and 40%-60% of patients diagnosed with GCA also have PMR.

The most serious complication of GCA is sudden blindness, a result of anterior ischemic optic neuropathy caused by ischemia secondary to inflammation of the ophthalmic artery supplying the optic nerve. Some patients may experience transient vision loss. All patients with suspected GCA should have temporal artery biopsy. Pathologic findings include a predominance of mononuclear cell infiltration or granulomatous inflammation, usually with multinucleated giant cells.

Scalp necrosis is a rare but potentially life-threatening complication.

The 2022 American College of Rheumatology (ACR) / European Alliance of Associations for Rheumatology (EULAR) classification criteria for GCA when a diagnosis of medium-vessel or large-vessel vasculitis has been made:

A patient aged 50 years or older; 6 or more of the following points are needed for diagnosis:

Clinical criteria

• Morning stiffness in the shoulders or neck, jaw or tongue claudication, new temporal headache, scalp tenderness, abnormal clinical examination of the temporal artery (such as diminished pulse, tenderness, or a hard, cord-like texture) (+2 each)
• Sudden visual loss (+3)

Laboratory, imaging, and biopsy criteria

• ESR ≥ 50 mm/hour or C-reactive protein ≥ 10 mg/L (+3)
• Positive temporal artery biopsy or temporal artery halo sign on ultrasound (+5)
• Bilateral axillary luminal damage (as seen on angiography, ultrasound, or fluorodeoxyglucose-positron emission tomography [FDG-PET]; +2)
• FDG-PET uptake throughout the aorta (+2)