Makindo Medical Notes

Giant cell arteritis (GCA) is a systemic arteritis that can cause preventable blindness if not treated promptly. It often presents in rheumatology, eye clinics, or stroke/TIA clinics. Approximately 20% of patients develop vision loss, which can be prevented with timely diagnosis and treatment.

About

• A vasculitis affecting mainly extracranial arteries
• Involves large and medium-sized arteries, typically in the external carotid system
• Predilection for external carotid, ciliary, and retinal arteries
• Risk of blindness is due to anterior ischaemic optic neuropathy
• Approximately 50% of patients may also present with symptoms of polymyalgia rheumatica (PMR)

Epidemiology

• Mean age of onset is 70 years
• Rarely occurs before age 50
• More common in Caucasians
• Female to male ratio is 3:1

Vessels Involved

• Intimal hyperplasia +/- thrombosis of the short posterior ciliary artery
• Posterior ciliary arteries are derived from the ophthalmic artery
• Ischemia of extraocular muscles can cause diplopia
• The central retinal artery may also be involved

Aetiology

• Possibly an immune response to an unidentified antigen
• Endovascular damage and cytokine-mediated inflammation cause localized ischaemia
• Subacute granulomatous inflammation with giant cells
• Th1 cell-mediated immune response with elevated IL-6 levels
• HLA-DRB1 is associated with a higher risk of developing GCA

American College of Rheumatology Criteria for GCA

Clinical Presentation

• Fever, weight loss, malaise, and fatigue
• Monocular visual loss, possibly transient, resembling TIA
• Abrupt, often unilateral headache
• Temporal artery tenderness
• Jaw or tongue ache and claudication (due to masseter or lingual artery involvement)
• Ischaemic stroke is rare as the internal carotid artery is usually unaffected
• Blindness may occur due to posterior ciliary artery occlusion
• Late-stage complications: aortitis, aortic aneurysm, aortic dissection

Investigations

• FBC: Normocytic normochromic anaemia
• ESR: Typically >50 mm/h, often higher; CRP elevated; ALP elevated in 30% of cases
• Colour Duplex USS: Shows a hypoechoic halo (vessel edema) and hourglass stenosis; these regress after 2 weeks of steroid treatment
• Gold Standard: Temporal artery biopsy (TAB) of an affected vessel. A long section is taken to account for skip lesions. Best performed within 2 weeks of diagnosis.
• Fluorescein Angiography: Diagnosis can be confirmed by demonstrating choroidal shutdown on fluorescein angiography.

Management

• If visual symptoms are present, refer to an eye hospital and start Prednisolone 1 mg/kg - often 60 mg/day immediately until diagnosis is confirmed or refuted. If no visual symptoms, refer to rheumatology or acute medicine. Start a PPI and bone protection with high dose steroids. Begin treatment prior to biopsy or USS results.
• Response to steroids is often rapid for generalized symptoms but is less effective once blindness occurs. Long-term management includes bone protection, diabetes screening, and other steroid-related issues in primary care. The steroid dose is gradually lowered over 18 months to 2 years.

References

• Hassan N et al. Giant Cell Arteritis. BMJ 2011 May 23;342:d3019