Key Facts

GCA is a medical emergency when visual symptoms are present. Steroids should be started immediately on clinical suspicion — never wait for biopsy results. Tocilizumab has transformed the management of relapsing/refractory GCA.

Epidemiology

Incidence ~20 per 100,000 in over-50s. Peak age 70-80 years. F:M 2-3:1. Northern European descent. Almost never occurs <50 years. Incidence increases with age.

Aetiology

• Granulomatous vasculitis of medium and large arteries
• Aetiology unknown; likely immune-mediated response triggered by infection or environmental factor in genetically susceptible individuals
• HLA-DRB1*04 association
• Dendritic cells in the adventitia of temporal arteries activate T cells → granulomatous inflammation

Pathophysiology

Dendritic cell activation in the adventitia → recruitment of CD4+ T cells and macrophages → granulomatous inflammation with giant cells → intimal hyperplasia → luminal narrowing/occlusion → ischaemia. Affects branches of external carotid (temporal, occipital, ophthalmic) and aorta (large vessel GCA). Visual loss: anterior ischaemic optic neuropathy (AION) from posterior ciliary artery occlusion → optic nerve head ischaemia.

Classic Features

• New-onset headache (most common — ~75%): temporal, unilateral or bilateral, persistent, often worse at night
• Scalp tenderness: pain when brushing hair or resting head on pillow
• Jaw claudication (~30-40%): pain in masseter muscles on chewing; strongest clinical predictor of positive biopsy
• Temporal artery abnormalities: tender, thickened, nodular, pulseless, or prominent
• Constitutional: malaise, weight loss, fever, fatigue
• PMR symptoms (~50%): bilateral shoulder/hip girdle pain and stiffness

Visual Symptoms (EMERGENCY)

• Amaurosis fugax: transient monocular visual loss (warning sign — urgent treatment)
• Anterior ischaemic optic neuropathy (AION): sudden painless visual loss (often irreversible)
• Diplopia: cranial nerve palsies (III, IV, VI)
• Visual loss may be bilateral if untreated (second eye at high risk in days-weeks)

Red Flags

• Any visual disturbance in suspected GCA → emergency → immediate high-dose steroids
• Jaw claudication → high specificity for GCA
• Tongue claudication (rare but highly specific)

Bloods (Urgent)

• ESR: typically >50 mm/hr (often >100); normal ESR does NOT exclude GCA (~5% have normal ESR)
• CRP: raised (more sensitive than ESR)
• FBC: normocytic anaemia, thrombocytosis common
• LFTs: raised ALP (~30%)
• Fibrinogen: raised

Temporal Artery Biopsy (Gold Standard)

• ≥1 cm sample (preferably ≥2 cm) from symptomatic side
• Perform within 14 days of starting steroids (histological changes persist for 2-6 weeks)
• Skip lesions: patchy inflammation means negative biopsy does not exclude GCA (sensitivity ~85%; consider bilateral biopsy)
• Histology: transmural granulomatous inflammation, giant cells (not always present), intimal hyperplasia, fragmented internal elastic lamina

Imaging

• Temporal artery ultrasound: hypoechoic halo sign (vessel wall oedema) — sensitivity ~77%, specificity ~96%; increasingly used as first-line; NICE NG100
• CTA/MRA/PET-CT: for large vessel GCA (aortitis, subclavian, axillary involvement)

Ophthalmology

• Urgent ophthalmology review if visual symptoms
• Fundoscopy: pale swollen optic disc (AION), cotton wool spots, central retinal artery occlusion

Immediate Treatment (NICE NG100)

GCA WITHOUT visual symptoms:

• Prednisolone 40-60mg OD: start immediately on clinical suspicion; do NOT wait for biopsy
• Taper slowly: reduce by 10mg every 2 weeks to 20mg, then by 2.5mg every 2-4 weeks to 10mg, then by 1mg every 1-2 months; typical treatment duration 1-2 years

GCA WITH visual symptoms (evolving/threatened visual loss):

• IV methylprednisolone 500mg-1g daily × 3 days → then oral prednisolone 60mg OD with slow taper
• Urgent ophthalmology review
• Same-day referral pathway

Steroid-Sparing Agent

• Tocilizumab 162mg SC weekly (anti-IL-6R; GiACTA trial — RR of relapse reduced by ~50%): NICE TA518 recommends for relapsing/refractory GCA; allows faster steroid taper
• Methotrexate 10-25mg weekly: moderate evidence as steroid-sparing; used if tocilizumab unavailable/contraindicated

Bone Protection

• All patients on long-term steroids: alendronate 70mg weekly + calcium/vitamin D supplementation (NICE NG100)
• PPI if on concurrent NSAID/aspirin

Low-Dose Aspirin

• Aspirin 75mg OD: consider in all GCA patients (reduces ischaemic events; some guidelines recommend routinely)

Monitoring

• ESR/CRP: serial monitoring (guide taper but treat clinically, not purely by markers)
• Blood glucose: steroid-induced diabetes
• BP: steroid-induced hypertension
• Bone density: DEXA if prolonged steroid use

Referral Criteria

• Rheumatology: all GCA for ongoing management and steroid taper
• Ophthalmology: any visual symptoms (same-day)
• Vascular: if large vessel GCA suspected

With prompt treatment, visual loss risk falls dramatically. Untreated: 15-20% develop permanent visual loss (often bilateral). Once visual loss is established, recovery is unlikely. GCA is a self-limiting condition — most patients can taper off steroids within 1-2 years. ~50% relapse during taper (tocilizumab reduces this). Large vessel GCA: risk of aortic aneurysm (~17% at 5 years) — long-term surveillance recommended. GCA does not significantly reduce life expectancy with appropriate treatment.

GCA Fast-Track Pathway (UK Best Practice)

Key Trial: GiACTA