Giant cell arteritis (GCA) is a type of autoimmune vasculitis that causes chronic inflammation of large and medium-sized arteries, in particular the carotid arteries, its major branches, and the aorta. GCA is most common in women over the age of 50 and of northern European descent, and approximately 50% of patients also have polymyalgia rheumatica. Patients usually present with constitutional symptoms (e.g., fever, weight loss, night sweats, fatigue, and malaise), new-onset headache, a tender, hardened temporal artery, jaw claudication, or amaurosis fugax. If there is strong clinical suspicion for GCA, glucocorticoids should be administered immediately, even prior to diagnostic workup if needed, to reduce the risk of permanent vision loss and cerebral ischemia. Laboratory studies typically show signs of inflammation (e.g., elevated erythrocyte sedimentation rate and CRP), and temporal artery biopsy and/or imaging (e.g., Duplex ultrasound) should be performed to confirm the diagnosis. The classic histopathological findings are mononuclear infiltration of the vessel wall and formation of giant cells. Patients should be referred to rheumatology for follow-up because most patients require long-term therapy with glucocorticoids (≥ 2 years).
- Local vascular damage
- Concentric intimal hyperplasia: macrophages and giant cells produce PDGF and VEGF → stimulate intimal proliferation → reduced blood flow and ischemia
- Constitutional symptoms
Clinical features of arterial inflammation
Cranial giant cell arteritis: involves the extracranial branches of the common carotid, internal carotid, and external carotid arteries (the temporal artery is the most commonly affected vessel)
New-onset unilateral (or bilateral) headache
- Can be pulse-synchronous, throbbing, dull
- Typically located over the temples
- Hardened and tender temporal artery
- Jaw claudication: jaw pain when chewing
- Vision loss: due to inflammation and occlusion of the ophthalmic artery and its branches
- New-onset unilateral (or bilateral) headache
- Large-vessel giant cell arteritis: less common; involves the aorta and its primary branches 
- Cranial giant cell arteritis: involves the extracranial branches of the common carotid, internal carotid, and external carotid arteries (the temporal artery is the most commonly affected vessel)
- Symptoms of (if both diseases are present)
Demonstration of arterial inflammation on imaging and/or histopathology is required to make a diagnosis of GCA. In patients with features of cranial GCA, the can be used to differentiate GCA from other forms of vasculitis. 
Laboratory studies 
- Inflammatory markers: initial laboratory test in suspected GCA
- Additional laboratory tests
Confirmatory diagnostic studies
All patients require imaging and/or a temporal artery biopsy to confirm the diagnosis. 
Temporal artery biopsy (gold standard)
- Consider in all patients with suspected GCA 
- High clinical suspicion for GCA despite inconclusive findings on imaging
- Findings: See “Pathology.”
- Important considerations
Do not delay therapy for TAB results in patients with a high clinical suspicion of GCA.
Duplex ultrasound (US) 
- Supportive findings 
- Less sensitive in detecting thoracic aortic involvement
Additional imaging studies 
- High clinical suspicion for GCA despite inconclusive duplex US 
- Suspected large-vessel GCA
Differential diagnoses of GCA
- Polymyalgia rheumatica
- Other vasculitides
- Other causes of monocular vision loss
- Other causes of constitutional symptoms
- Other causes of headache: See “ .”
Clinical criteria to differentiate GCA from other forms of vasculitis 
These criteria were developed in 1990 by the American College of Rheumatology (ACR) to differentiate cranial GCA from other forms of vasculitis. They should not be used to diagnose cranial GCA, for which they have low sensitivity and low positive predictive value. 
|ACR criteria for the classification of GCA |
|Aged ≥ 50 years at disease onset||1|
|Examination findings||Abnormalities of the temporal artery (decreased pulsation or tenderness to palpation)||1|
Histopathological abnormalities in the temporal artery
|Elevated ESR (≥ 50 mm/h)||1|
The differential diagnoses listed here are not exhaustive.
- Initial high-dose glucocorticoid therapy for 2–4 weeks is indicated for all patients with newly diagnosed GCA or recurrent GCA symptoms.
- After the completion of high-dose therapy, taper the dose of glucocorticoid therapy to a maintenance dose.
Glucocorticoid therapy 
This is the mainstay of treatment for patients with GCA.
Initial high-dose therapy (induction therapy)
- Indication: all patients with new-onset or recurrent GCA
- Important consideration: Initiate before diagnostic workup (e.g., before TAB) if clinical suspicion for GCA is high to minimize the risk of complications such as vision loss or stroke
- Uncomplicated disease: oral glucocorticoids, e.g., prednisolone
- Ischemic organ damage (e.g., impaired vision): Consider initial pulse therapy with IV glucocorticoids before oral glucocorticoids. 
- Duration: Approx. 2–4 weeks 
Maintenance therapy 
- Initiate after acute symptoms have resolved.
- Slowly taper glucocorticoids to the lowest dose needed to control symptoms. 
- Length of treatment: no consensus; generally ≥ 2 years 
- Administer prophylactic measures to prevent complications of glucocorticoid therapy as needed.
- Glucocorticoid-sparing therapy 
- Not routinely recommended
- Consider in patients with preexisiting cardiovascular or cerebrovascular disease 
- Start treatment with glucocorticoids immediately.
- Assess inflammatory markers.
- Confirm arterial inflammation via temporal artery biopsy and/or imaging.
- Consider further imaging (extracranial duplex ultrasound, MRI, CTA, or PET scan) if large-vessel involvement is suspected.
- Refer all patients to rheumatology.
- Refer patients with evidence of complications to the appropriate specialists.
- Consider tocilizumab or methotrexate in patients at high risk of complications from long-term glucocorticoid therapy
Begin treatment as soon as GCA is suspected. Do not wait for a biopsy.