Decision support only — not a substitute for rheumatology, ophthalmology, or the ACR/EULAR/BSR guidelines. GCA is a "treat-now, confirm-later" emergency: the whole point of acting on suspicion is to save sight, and once an eye is lost it rarely recovers. Then comes the long tail — a steroid course measured in years, a relapse rate near 50%, and the steroid toxicity of treating people who are mostly over 70. Verify all doses.
1 The acute decision — act on suspicion
Suspected, no visual symptomsuncomplicated
New headache, jaw claudication, scalp tenderness, PMR, raised inflammatory markers.
Prednis(ol)one 40–60 mg daily (≥0.75 mg/kg) — start now, don't wait for biopsy or bloods.
Visual symptomsneuro-ophthalmic emergency
Amaurosis fugax, diplopia, or any visual loss.
IV methylprednisolone 500 mg–1 g daily × 3 days, then high-dose oral pred. Don't delay the oral drug while arranging IV.
Confirm — but don't wait
Diagnosis still needs securing.
Temporal-artery ultrasound (halo) and/or biopsy within ~2 weeks; image the aorta/large vessels if that phenotype is suspected (§3). Steroids first, always.
Plan the long gamefrom day one
This is a multi-year illness.
Map the taper, add steroid-sparing (tocilizumab, upadacitinib, or methotrexate) where indicated, and start bone/gastric/glucose protection (§4–5).
With established visual loss the realistic goal is protecting the second eye — the affected eye seldom recovers, and around 1 in 5 patients still lose vision. Steroids don't sabotage the biopsy: it stays positive for roughly two weeks, so there is never a reason to withhold treatment while waiting.
2 Recognise it — features & phenotypes
The clinical picture
- WhoAge >50 (mean ~73), women ~2.6:1; PMR overlaps in roughly half.
- CranialNew temporal headache, jaw claudication (high-risk), scalp tenderness, temporal artery thickened/tender/pulseless, visual symptoms.
- Large-vesselAortitis, limb claudication, bruits, prominent constitutional symptoms; often fewer cranial features and more relapses.
- SystemicFever, weight loss, malaise; rarely tongue or scalp necrosis.
Bloods — helpful, not decisive
- MarkersESR often >50 (can be very high) and raised CRP; normocytic anaemia, thrombocytosis.
- The trap~4% have normal inflammatory markers — normal ESR/CRP does not exclude GCA when the story fits.
- Jaw + eyeJaw claudication and visual symptoms carry the highest ischaemic risk — treat these hardest and fastest.
3 Confirm the diagnosis
Ultrasound — often first now
- SignsHalo sign (hypoechoic wall oedema) and non-compressible artery; scan temporal and axillary arteries.
- PathwayFast-track ultrasound clinics cut diagnostic delay and visual loss; first-line where expertise exists TABUL.
Temporal artery biopsy
- Yield≥1 cm segment (skip lesions); transmural inflammation ± giant cells. Do within ~2 weeks of steroids.
- LimitA negative biopsy doesn't exclude GCA — skip lesions and large-vessel disease are missed.
Large-vessel imaging
- WhenLV phenotype, prominent constitutional symptoms, or a normal cranial work-up with high suspicion.
- HowPET-CT, CT/MR angiography for aortitis and branch involvement. Classify with the 2022 ACR/EULAR criteria.
4 Glucocorticoids & the long taper
The taper
- Induction40–60 mg (or IV pulse for visual loss) until symptoms and markers settle (2–4 weeks).
- Reduce to15–20 mg by 2–3 months, then ≤5 mg by 12 months; total course usually 18–24 months.
- RealityNearly half relapse during the taper; slower reductions and steroid-sparing agents reduce it. Alternate-day dosing relapses more — avoid.
Protect against the steroid
- BoneSteroid-induced osteoporosis in an elderly cohort → bisphosphonate + calcium/vitamin D from the outset.
- Gut/glucosePPI for gastroprotection; monitor and treat steroid hyperglycaemia; watch BP, weight, mood, cataract, infection.
- AspirinNo longer routinely recommended — the evidence is weak; use only for a separate indication.
5 Steroid-sparing therapy
Two targeted agents now have phase 3 evidence, working through different pathways — IL-6 blockade (tocilizumab) and JAK1 inhibition (upadacitinib). Both cut cumulative steroid and improve sustained remission; add either for relapsing disease or high steroid-toxicity risk.
Tocilizumab (IL-6 receptor inhibitor)
- EvidenceSustained glucocorticoid-free remission and roughly halved cumulative steroid GiACTA; ACR/EULAR recommend it with the taper for relapsing disease or high steroid-toxicity risk.
- Dose162 mg SC weekly or fortnightly. PBS-listed in Australia for relapsing/refractory or steroid-intolerant GCA — confirm current criteria.
- Relapse~40% relapse after stopping — many need longer-term therapy.
Upadacitinib (oral JAK1 inhibitor) new
- EvidenceFirst new drug class since tocilizumab. Sustained remission ~46% vs 29% (placebo + longer taper), with less flare and lower cumulative steroid SELECT-GCA.
- Dose15 mg once daily, oral — the 7.5 mg dose did not work. FDA and EU approved 2025; confirm TGA/PBS status locally.
- AppealOral, not injectable, and doesn't blind CRP the way IL-6 blockade does.
Cautions & monitoring
- TCZ masks CRPIL-6 blockade normalises CRP/ESR regardless of disease or infection — monitor clinically. GI perforation risk; caution with diverticular disease.
- JAK classIn over-50s, weigh VTE, MACE, serious infection (esp. zoster) and malignancy signals — the population most likely to have GCA is the one these warnings target. SELECT-GCA showed no significant CV excess, but the class labelling stands.
Methotrexate & choosing
- MTXA modest steroid-sparing alternative when a targeted agent is unavailable or unsuitable.
- Which agentNo head-to-head yet. Tocilizumab has the longer track record and PBS pathway; upadacitinib offers an oral option and preserved CRP — driven by access, comorbidity and patient preference.
- IL-17Secukinumab looked promising in phase 2 but did not meet its phase 3 endpoint in GCA — not a current option.
6 Relapse, monitoring & the aortic tail
Relapse & monitoring
- RelapseRecurrent cranial symptoms, PMR, or rising markers on tapering → step the steroid back up and add/optimise tocilizumab.
- MarkersESR/CRP track disease off tocilizumab; unreliable on it. A visual relapse is an emergency, as at presentation.
- CourseRelapsing-remitting; many run beyond two years, some become steroid-dependent.
The late complication
- AortaLarge-vessel GCA carries a late risk of aortic aneurysm and dissection — years downstream.
- SurveillanceConsider periodic aortic imaging in those with known large-vessel involvement.
- PMRWhen GCA and PMR coexist, treat the GCA — its steroid requirement is higher, and cranial/visual symptoms must always be asked about in PMR.
Guidelines. 2021 ACR/Vasculitis Foundation guideline for GCA & Takayasu; EULAR recommendations for large-vessel vasculitis (2018, update); BSR guideline for GCA (2020); 2022 ACR/EULAR GCA classification criteria; eTG; PBS (tocilizumab).
Trials & evidence. GiACTA (tocilizumab in GCA, NEJM 2017 — sustained steroid-free remission, steroid-sparing); SELECT-GCA (upadacitinib 15 mg, NEJM 2025 — first oral JAK inhibitor approved for GCA, 2025); TABUL (ultrasound vs biopsy diagnostic accuracy); observational glucocorticoid taper & relapse cohorts. Glucocorticoid dosing rests on decades of practice rather than placebo-controlled trials (which would be unethical given the vision risk).
Caveats. Treat on clinical suspicion before confirming — sight is the stake. Normal inflammatory markers (~4%) and a negative temporal-artery biopsy do not exclude GCA. Tocilizumab abolishes CRP/ESR as activity or infection markers. Aspirin is no longer routine. PBS tocilizumab criteria are specific and change — confirm locally. Verify all doses. Companion to the rheumatology/general-medicine set (osteoporosis, PMR).