Giant Cell Arteritis

The commonest form of primary systemic vasculitis in adults over fifty, characterised by granulomatous inflammation of large and medium sized arteries, principally the extracranial branches of the carotid artery, with a strong predilection for the temporal artery and a close epidemiological and pathogenic relationship with polymyalgia rheumatica.

It represents a medical emergency given the risk of sudden, irreversible visual loss if treatment is delayed.

Pathophysiology

T cell mediated granulomatous inflammation targets the arterial wall, causing intimal hyperplasia, luminal narrowing and, in the ophthalmic and posterior ciliary arteries, ischaemic optic neuropathy, the mechanism underlying the feared visual complications of this disease.

The elastic lamina rich vessels of the aortic arch branches are preferentially affected, explaining the characteristic distribution of clinical involvement.

• New onset headache, typically temporal or occipital, is the commonest presenting symptom, often accompanied by scalp tenderness (particularly noticed when combing hair or resting the head on a pillow).

• Jaw claudication, pain developing in the jaw muscles with chewing and relieved by rest, is a highly specific symptom for this condition and should be actively asked about in any patient over fifty with new headache and elevated inflammatory markers.

• Visual symptoms, including amaurosis fugax, diplopia and, most seriously, sudden painless visual loss from anterior ischaemic optic neuropathy, represent the most urgent manifestation given the risk of permanent blindness, which can affect the second eye within days if treatment is not commenced promptly.

• Constitutional symptoms (fever, weight loss, fatigue, night sweats) are common, and a proportion of patients present with these systemic features alone without classical cranial symptoms, an important atypical presentation to recognise.

• Polymyalgia rheumatica symptoms (bilateral shoulder and hip girdle pain and stiffness) coexist in a substantial proportion of patients at diagnosis or develop subsequently.

• Large vessel involvement (aortitis, upper limb claudication, asymmetrical pulses or blood pressure) occurs in a meaningful minority and may be present without classical cranial symptoms, an increasingly recognised phenotype requiring imaging based assessment.

• Temporal artery tenderness, thickening or reduced pulsation on examination supports the diagnosis, though a normal examination does not exclude it, particularly with large vessel predominant disease.

• Suspected giant cell arteritis constitutes a medical emergency, and treatment with high dose corticosteroids should not be delayed for investigation given the risk of irreversible visual loss, with diagnostic testing pursued promptly and in parallel with treatment initiation.

• Erythrocyte sedimentation rate and C reactive protein are typically markedly elevated and support the diagnosis, though a small proportion of biopsy confirmed cases have normal inflammatory markers, so a normal result does not exclude the diagnosis in a strongly suggestive clinical picture.

• Temporal artery biopsy remains an important confirmatory investigation, ideally performed within one to two weeks of starting corticosteroids. The characteristic histological changes (granulomatous inflammation with giant cells, though giant cells are not present in all positive biopsies) typically persist for this period despite treatment.

  A negative biopsy does not exclude the diagnosis, given the patchy (skip lesion) nature of arterial involvement.

  Treatment should not be withheld or stopped on the basis of a negative biopsy in a clinically convincing case.

• Temporal artery ultrasound, demonstrating a characteristic hypoechoic halo around the vessel lumen, is increasingly used as a rapid, non invasive alternative or complement to biopsy, with good sensitivity and specificity in experienced hands.

• Magnetic resonance angiography, computed tomography angiography or positron emission tomography are used to assess for large vessel involvement, particularly in patients with atypical presentations, constitutional symptoms without classical cranial features, or asymmetrical limb pulses or blood pressure.

• Urgent ophthalmological assessment is required for any patient with visual symptoms, both to document baseline visual function and to identify ischaemic optic neuropathy or other ocular manifestations.

• High dose corticosteroids (prednisolone forty to sixty milligrams daily) should be started immediately on clinical suspicion, without waiting for biopsy or other confirmatory testing, given the risk of irreversible visual loss with any delay.

• Established or threatened visual loss warrants intravenous methylprednisolone (typically five hundred milligrams to one gram daily for three days) before transitioning to high dose oral corticosteroids, reflecting the urgency of preventing bilateral involvement and any possibility of partial visual recovery.

• The corticosteroid dose is maintained for a period once symptoms and inflammatory markers have settled, then tapered gradually over one to two years, guided by symptoms and inflammatory markers, with relapse managed by returning to the last effective dose.

• Tocilizumab is approved as a steroid sparing agent and has transformed management for many patients, significantly reducing cumulative corticosteroid exposure and relapse rates, and is increasingly used alongside corticosteroids from diagnosis in patients at higher risk of relapse or corticosteroid toxicity.

• Low dose aspirin is considered in the absence of contraindication, given evidence suggesting a reduction in ischaemic complications, though this practice varies and should be individualised.

• Bone protection with calcium, vitamin D and bisphosphonate therapy is essential given the prolonged, often high cumulative corticosteroid exposure in an older population at elevated baseline fracture risk.

• Regular monitoring for disease relapse (recurrence of cranial symptoms, rising inflammatory markers), for large vessel complications (aortic aneurysm, which can develop or progress silently over years and warrants periodic imaging surveillance in patients with a large vessel phenotype), and for corticosteroid related adverse effects underpins long term follow up.

• Patient education regarding the symptoms of relapse and the importance of urgent review for any new visual symptoms is essential given the potential for sudden, severe complications even after apparent disease control has been achieved.