Giant Cell Arteritis
Rheumatology
Illness script · Rheumatology
Giant Cell Arteritis
Large-vessel granulomatous vasculitis of the aorta and its branches, classically affecting the temporal artery in patients >50.
This illness script for Giant Cell Arteritis covers predisposing factors, classic presentation, mechanism, workup, management, and the clinical pivots that separate it from look-alikes—written for USMLE Step 1 and clerkship reasoning.
01
Predisposing factors
- Age >50 (peak 70–80); rarely affects younger patients
- Female predominance (3:1)
- Northern European ancestry
- Strong association with polymyalgia rheumatica (PMR) — 40–60% overlap
- HLA-DR4 genetic association
02
Presentation
- New-onset temporal headache (unilateral, throbbing) in patient >50
- Jaw claudication — pathognomonic for GCA
- Scalp tenderness; thickened, nodular, non-pulsatile temporal artery on exam
- Visual symptoms: amaurosis fugax → irreversible blindness if untreated
- Constitutional symptoms: fever, fatigue, weight loss
- May coexist with PMR: bilateral shoulder/hip girdle stiffness worse in AM
03
Pathophysiology
- CD4+ T-cell–driven granulomatous inflammation of medium-to-large vessel walls
- Intimal hyperplasia → luminal narrowing → ischemia of end organs
- Cytokine cascade (IL-6, IFN-γ) drives systemic inflammation and elevated ESR/CRP
- Involvement of ophthalmic artery → anterior ischemic optic neuropathy → blindness
04
Diagnostics
- ESR >50 mm/hr (often >100); CRP also markedly elevated — best initial tests
- Temporal artery biopsy — gold standard; skip lesions require ≥1–2 cm sample
- Biopsy within 2 weeks of steroid initiation (do NOT delay steroids for biopsy)
- High-resolution ultrasound: hypoechoic halo sign around temporal artery — emerging tool
- PET-CT useful for detecting large-vessel (aortic) involvement
05
Management
- Start high-dose prednisone (40–60 mg/day) IMMEDIATELY — before biopsy if vision threatened
- Visual symptoms → IV methylprednisolone 1 g/day × 3 days then oral taper
- Add tocilizumab (IL-6 inhibitor) as steroid-sparing agent — FDA approved for GCA
- Aspirin 81 mg/day reduces ischemic events (cranial, ocular)
- Taper steroids over 1–2 years guided by symptoms and inflammatory markers
06
Clinical pivots
How to separate this script from the look-alikes that show up on exams and on the wards.
Polymyalgia Rheumatica
PMR lacks cranial/ischemic symptoms; jaw claudication and headache point to GCA
Migraine
Migraine rarely new-onset after 50; lacks elevated ESR/CRP and temporal artery tenderness
Trigeminal Neuralgia
Trigeminal neuralgia is electric/lancinating, not throbbing; no systemic inflammation or jaw claudication
Takayasu Arteritis
Takayasu affects patients <40 and targets aortic arch; GCA is age >50 with cranial features
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Educational use only. This illness script is a study framework, not medical advice. Confirm decisions with current guidelines and your clinical supervisors.