Giant Cell Arteritis (GCA)
Giant cell arteritis (GCA) is a granulomatous vasculitis affecting large- and medium-sized arteries. When it affects extra-cranial branches of the carotid artery, it is referred to as temporal arteritis (cranial GCA).
Causes and Risk Factors
The cause of GCA is unknown, it is thought to be an immune-mediated vasculitis.
Risk factors include: [Ref]
- Advanced age
- Primarily affects those >50 y/o
- Peak incidence: 70-79 y/o
- Females
- Northern European ancestry
Clinical Features
GCA encompass a wide spectrum of symptoms that are generally classified into classic cranial (temporal) manifestations and extracranial manifestations.
Classic Temporal Arteritis (Cranial Manifestation)
Temporal arteritis presents with features caused by inflammation of the cranial branches of the carotid arteries: [Ref]
- New-onset headache or change in pre-existing headache – most common presenting symptom
- Usually a temporal headache
- But the headache can also be frontal, occipital, unilateral or generalised
- Often accompanied by scalp tenderness or hyperesthesia
- Temporal artery abnormality
- Tenderness / thickening / nodularity (present up to 30%)
- Red overlying skin
- Reduced / absent pulsation
- Jaw and tongue claudication
- Pain / fatigue in the mandible +/- tongue which is triggered by chewing which subsides when chewing stops
- Visual disturbances, including
- Abrupt transient vision loss (often described as a curtain covering the visual field)
- Painless permanent vision loss
- Diplopia
- Change in colour vision
- Constitutional symptoms (e.g. fever, malaise, depression, anorexia, night sweats, weight loss)
- Strokes and TIAs (characteristically affect the vertebrobasilar system, rather than the intracranial vessels)
None of the GCA signs or symptoms is pathognomonic, they are all very non-specific.
Polymyalgia rheumatica (PMR) and giant cell arteritis (GCA) are closely associated [Ref]
- 16-21% of patients with PMR have GCA
- 40-60% of patients with GCA have PMR
See the Polymyalgia Rheumatica (PMR) article for additional information.
Extracranial Manifestation
Extracranial manifestations can be classified by the affected vessel: [Ref]
| Affected vessel | Clinical manifestation |
|---|---|
| Aorta |
|
| Subclavian artery and branches |
|
| Femoral artery and branches |
|
Complications
Key complications include:
- Loss of vision
- Most common mechanism: anterior ischaemic optic neuropathy (occlusion of the short posterior ciliary arteries supplying the optic nerve)
- Causes abrupt, painless monocular visual loss
- Fundoscopy classically shows a pale (“chalky-white), swollen optic disc
- May also cause retinal arterial occlusion
- Most common mechanism: anterior ischaemic optic neuropathy (occlusion of the short posterior ciliary arteries supplying the optic nerve)
- ↑ Risk of cardiovascular disease (including MI, heart failure, stroke, PAD)
Investigation and Diagnosis
GCA is considered a medical emergency
- Patients with suspected GCA should be urgently reviewed by rheumatology (ideally same working day)
- Those with new visual loss or double vision must be referred to ophthalmology on the same day
Important: if GCA is strongly suspected, treat with high-dose corticosteroids immediately. Do NOT delay treatment while awaiting laboratory or imaging results.
A diagnostic work-up for suspected GCA includes:
| Category | Description | Interpretation |
|---|---|---|
| Clinical examination |
|
|
| Laboratory tests |
|
Inflammation may result in:
|
| Confirmatory diagnostic test | Initial test: temporal artery ultrasound | Possible findings include:
|
| Definitive test: temporal artery biopsy | Characteristic findings:
Important notes:
|
|
Disclaimer: BSR guidelines recommend selecting the confirmatory diagnostic test based on the pretest probability of GCA, instead of the blanket rule of ultrasound as initial test and biopsy as the definitive test:
- Low probability → a -ve ultrasound should prompt consideration of alternative diagnoses
- Medium probability → ultrasound first, and perform biopsy if ultrasound is equivocal
- High probability → positive ultrasound alone can confirm diagnosis, though biopsy may still be done for confirmation
Other investigations to exclude alternative diagnoses or identify increased risk of glucocorticoid-related adverse effects:
- Baseline U&E, HbA1c, calcium, LFT
- Screening tests for risk of serious infection (e.g. urine dipstick, chest X-ray, latent tuberculosis screening)
- Screening test for osteoporosis risk (e.g. TSH, vitamin D, bone density test, DEXA)
Management
GCA is considered a medical emergency
- Patients with suspected GCA should be urgently reviewed by rheumatology (ideally same working day)
- Those with new visual loss or double vision must be referred to ophthalmology on the same day
Initial Acute Management
High-dose steroid is the cornerstone therapy for GCA. The route and dose depend on whether there are visual changes:
| YES visual changes (any new visual loss or double vision) | 1st line: IV methylprednisolone 0.5-1 g up to 3 consecutive days before commencing oral prednisolone
Alternative: oral prednisolone 60-100 mg per day |
| NO visual changes | 1st line: oral prednisolone 40-60 mg per day
|
Important: if GCA is strongly suspected, treat with high-dose corticosteroids immediately. Do NOT delay treatment while awaiting laboratory or imaging results.
Ongoing Management
Maintain the initial steroid dose until symptoms and inflammatory markers (CRP, ESR) normalise:
- Once in remission, steroid dose should be tapered to zero over 12-18 months, provided there is no return of GCA symptoms, signs or laboratory markers of inflammation
- Some patients may require low doses of corticosteroids for several further years
For those at high risk of steroid toxicity or relapse while tapering, consider adding steroid-sparing agents while tapering steroid dose:
- Methotrexate, or
- Tocilizumab (strong recommendation)
References