Makindo Medical Notes.com

A systemic arteritis which may cause preventable cause of blindness that may present to rheumatology, eye clinic or stroke TIA clinic. Twenty per cent of patients develop loss of vision, which can be prevented with timely recognition and treatment.

About

• A vasculitis affecting mainly extracranial arteries
• Large and medium-sized arteries usually external carotid system
• Predilection for the external carotid, ciliary and retinal arteries
• Risk is blindness due to an anterior ischaemic optic neuropathy
• About half describe a PMR type syndrome

About

• Mean age of onset is 70
• Rare before age 50
• Commoner in Caucasians
• Female > male 3:1

Vessels Involved

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

Aetiology

• Possibly an immune response to an antigen of some sort
• Endovascular damage and cytokine-mediated inflammation
• Causes localised ischaemia and possible infarction
• Subacute granulomatous inflammation with giant cells
• Th1 cell-mediated immune response with elevated IL-6
• HLA-DRB1 being associated with a higher risk of developing GCA.

American College of Rheumatology criteria for GCA

*Sensitivity of 93.5% and a reported specificity of 91.2% for the classification of giant-cell arteritis compared with other vasculitides.

Clinical

• Fever, weight loss, malaise, fatigue
• Monocular visual loss may be transient and resemble TIA
• Abrupt onset often unilateral Headache
• Temporal artery tenderness (Temporal artery)
• Jaw ache and claudication (masseter)
• Tongue ache and claudication (lingual artery)
• Ischaemic Stroke is rare as the internal carotid artery is usually not inflamed.
• Blindness due to posterior Ciliary artery occlusion. The disc may be pale and swollen with haemorrhage and later atrophy. There may be no cherry-red spot as the choroid is also infarcted if the Posterior ciliary artery or ophthalmic artery involved
• Later disease: aortitis, aortic aneurysm, dissection of the aorta

Giant cell arteritis

Investigations

• FBC: Normocytic normochromic anaemia
• ESR almost always > 50 and higher. CRP elevated. ALP elevated in 30%
• Colour Duplex USS shows a hypoechoic halo due to vessel oedema and there may be hourglass stenosis but does not add to diagnostic accuracy over the clinical examination. This all regresses after 2 weeks of steroids.
• Gold standard is temporal artery biopsy (TAB) of an affected vessel or some biopsy both. A long section is taken as there are skip lesions. Should be done asap usually within 2 weeks. The best question to ask is “If the biopsy is negative, will I continue to treat for GCA?" If the answer is yes, then a biopsy is of limited value.
• Fluorescein Angiography: Diagnosis can be made by demonstrating choroidal shutdown on fluorescein angiography.

Management

• If visual symptoms then refer to the eye hospital and start Prednisolone 60 mg/day until diagnosis confirmed. If confirmed reduce the dose over 18 months once symptoms and laboratory abnormalities resolve, the dose of corticosteroid can then be reduced and usually stopped within two years.
• If no visual symptoms, then refer to acute medicine or rheumatology depending on local set-up. Start Prednisolone 1 mg/kg and PPI and bone protection now or when diagnosis confirmed. If the diagnosis is confirmed, continue steroids which will be reduced over time. Refer for specialist review.
• Do not wait until biopsies are taken as they take 2 weeks- start immediately and review diagnosis and management after TAB result known. Rapid response to steroids within hours/days for generalised symptoms but steroids are rarely useful after blindness. Manage long term bone protection and screening for diabetes and other related issues in primary care.

References

• Giant cell arteritis. Hassan N et al. BMJ 2011 May 23;342:d3019