Giant cell arteritis (temporal arteritis) is an idiopathic, systemic, non-infectious granulomatous vasculitis targeting large- and medium-calibre arteries, with a marked predilection for the extracranial branches of the carotid artery system, particularly the temporal, ophthalmic, and posterior ciliary arteries, alongside the aorta and its primary aortic arch branches 2,6. Clinically manifesting almost exclusively in individuals older than 50 years, the disease process is driven by cell-mediated immune responses that remodel the arterial wall, culminating in luminal stenosis, thrombosis, and devastating ischaemic complications such as permanent visual loss and stroke 6,7.
1. Etiology & Risk Factors
- Age Predilection: Virtually restricted to adults aged 50 years and older, with peak incidence occurring between the seventh and eighth decades of life 2.
- Sex and Ethnicity: Higher incidence among females (approximately 2:3 to 3:1 female-to-male ratio) and individuals of Northern European descent, particularly Scandinavian populations 2.
- Genetic Susceptibility: Strong association with human leukocyte antigen (HLA) class II alleles, specifically HLA-DRB1*04 subtypes, which influence the autoimmune presentation and severity 6.
- Environmental Triggers: Postulated infectious triggers—including varicella-zoster virus, Chlamydia pneumoniae, and parainfluenza viruses—that may initiate arterial wall antigen recognition, though no single definitive pathogen has been isolated 6.
- Anatomic Predisposition: High concentration of elastic tissue in medium- and large-sized arteries provides a specific target for immunologically active dendritic cells residing within the medial-adventitial border 2,6.
2. Pathophysiology
The pathogenesis of giant cell arteritis represents an antigen-driven, T-cell mediated immune reaction originating in the vascular wall 6. The pathological cascade initiates when resident dendritic cells within the adventitia recognize environmental or endogenous stress signals, resulting in the recruitment and activation of CD4+ T lymphocytes 6. These activated T cells secrete high levels of interferon-gamma and interleukin-12, driving the differentiation and accumulation of macrophages within the arterial media 6.
Within the media, macrophages fuse to form multinucleated giant cells—the histopathological hallmark of the disease—and release reactive oxygen species, matrix metalloproteinases, and growth factors including platelet-derived growth factor (PDGF) and vascular endothelial growth factor (VEGF) 6. These secreted factors stimulate the migration and proliferation of vascular smooth muscle cells (VSMCs) from the media into the intima, driving profound intimal hyperplasia 6. Concurrently, fragmentation of the internal elastic lamina occurs, compromising structural integrity and leading to luminal compromise, downstream tissue ischaemia, and aneurysm formation in large vessels like the aorta 3,6.
3. Clinical Presentation & Classic Clinical Signs
- History & Cardinal Symptoms:
- Temporal Headache: New-onset, localized, throbbing, or lancinating headache, frequently over the temporal or occipital regions, representing the most common cranial symptom.
- Scalp Tenderness: Hypersensitivity of the scalp, characteristically exacerbated by minor stimuli such as brushing hair, wearing glasses, or resting the head on a pillow.
- Jaw Claudication: Ischaemic pain and fatigue in the masticatory muscles (masseter and temporalis) triggered by chewing or talking, reflecting involvement of the facial and maxillary arterial branches.
- Visual Disturbances: Transient monocular visual loss (amaurosis fugax), diplopia due to extraocular muscle ischaemia, or acute, painless, permanent visual loss caused by anterior ischaemic optic neuropathy (AION) 7.
- Constitutional Symptoms: Low-grade fever, profound fatigue, anorexia, involuntary weight loss, and night sweats occurring in up to half of patients.
- Polymyalgia Rheumatica (PMR): Symmetric aching and morning stiffness exceeding 45 minutes in the shoulder and pelvic girdle muscles, present concurrently in 40–60% of patients 4.
- Physical Examination & Named Clinical Signs:
- Temporal Artery Abnormalities: Inspection and palpation often reveal nodular, thickened, tortuous, and prominent temporal arteries that demonstrate diminished or absent pulsations and exquisite tenderness.
- Extracranial Vascular Findings: Bruits over the subclavian, axillary, or carotid arteries, or asymmetry in upper extremity blood pressures, indicating large-vessel vasculitis (large-vessel GCA) 3.
- Fundoscopic Examination: Pale, swollen optic disc with blurred margins (anterior ischaemic optic neuropathy) or retinal arteriolar attenuation during acute ophthalmological assessment.
4. Diagnostic Workup & Interpretation (Laboratory, Imaging & ECG/Pathology)
| Diagnostic Modality / Test | Expected Clinical & Radiological / Laboratory Finding |
|---|---|
| Gold-Standard Investigation | Colour Duplex Ultrasound demonstrating the non-compressible, hypoechoic 'halo sign' around the temporal and axillary arteries; Temporal Artery Biopsy revealing granulomatous panarteritis with multinucleated giant cells and internal elastic lamina fragmentation 1. |
| Laboratory Panel | Markedly elevated erythrocyte sedimentation rate (ESR typically greater than 50 mm/hr) and elevated C-reactive protein (CRP), alongside a normocytic anaemia of chronic disease and thrombocytosis. |
| Imaging / Radiology (X-ray, US, CT, MRI) | Colour Doppler ultrasonography of temporal and axillary vessels; Magnetic Resonance Angiography (MRA) or Computed Tomography Angiography (CTA) revealing mural thickening, stenosis, or aneurysm formation in the aorta and primary branches 3. |
| ECG / Histopathology / Procedural | Histopathological verification demonstrating CD4+ T-lymphocyte and macrophage infiltration, destruction of the media, and intimal expansion; 18F-FDG PET-CT showing active linear vascular wall fluorodeoxyglucose uptake in large-vessel disease 3. |
5. Staging, Classification & Clinical Scoring Systems
| Criterion / Stage / Score Component | Clinical Threshold, Points & Management Implication |
|---|---|
| 2022 ACR / EULAR Classification Criteria | Classification requires a score of >=6 points based on weighted clinical items: Age >=65 years (+3), morning stiffness in shoulders (+2), jaw claudication (+2), new temporal headache (+2), scalp tenderness (+2), visual loss (+3), ESR >=50 mm/hr or CRP >=10 mg/L (+3), temporal artery abnormality on ultrasound (+5) or biopsy (+5) 1. |
| Anatomical Subtyping | Categorised into Cranial GCA (predominant headache, jaw claudication, high risk of blindness) and Large-Vessel GCA (aortitis, limb claudication, risk of aneurysm and dissection) 3,6. |
6. Differential Diagnosis
| Differential Condition | Distinguishing Clinical, Biochemical & Imaging Features |
|---|---|
| Polymyalgia Rheumatica (Isolated PMR) | Presents with shoulder and hip girdle stiffness and elevated inflammatory markers, but completely lacks cranial symptoms (headache, jaw claudication, visual loss) and temporal artery tenderness 4. |
| Primary Angiitis of the Central Nervous System (PACNS) | Restricted to the brain and spinal cord vasculature; presents with focal neurological deficits, encephalopathy, and seizures, with normal temporal arteries and negative temporal artery biopsies. |
| Takayasu Arteritis | Affects younger individuals (typically age <40 years), primarily involving the aorta and its major branches with absent cranial manifestations and distinctive angiographic findings. |
| Temporomandibular Joint (TMJ) Syndrome / Dental Disease | Causes localized jaw pain and tenderness exacerbated by chewing, but lacks systemic inflammation, elevated ESR/CRP, scalp tenderness, and visual symptoms. |
7. Management & Treatment Protocol
- Initial Stabilization & Resuscitation:
- Immediate ophthalmology and rheumatology consultation upon clinical suspicion of cranial or visual involvement.
- Prevention of permanent visual loss requires starting glucocorticoids immediately without waiting for diagnostic imaging or biopsy results 1.
- First-Line Medical / Pharmacological Therapy (with exact adult dosing):
- With Visual Symptoms: Intravenous Methylprednisolone 500–1000 mg daily for 3 consecutive days, followed by oral Prednisolone 60 mg daily 1.
- Without Visual Symptoms: Oral Prednisolone 40–60 mg daily as a single morning dose 1.
- Steroid-Sparing Agent: Initiation of Tocilizumab (an interleukin-6 receptor antagonist) administered subcutaneously at 162 mg weekly (or IV equivalent per weight-based protocols) alongside glucocorticoids to reduce cumulative steroid exposure and prevent relapses 1,7.
- Bone Protection: Concurrent prescription of elemental calcium, vitamin D, and a bisphosphonate (e.g., Alendronate 70 mg weekly) to prevent glucocorticoid-induced osteoporosis.
- Antiplatelet Therapy: Low-dose aspirin (75–100 mg daily) considered in the absence of absolute contraindications to reduce ischaemic visual and cerebrovascular events.
- Surgical / Interventional Indications:
- Surgical evaluation and intervention (endovascular stenting or open surgical repair) indicated for progressive aortic aneurysms, dissections, or severe limb-threatening stenosis arising from large-vessel complications 3,7.
8. Complications & Prognosis
- Visual Loss: Permanent monocular or binocular blindness resulting from anterior ischaemic optic neuropathy or central retinal artery occlusion, occurring in up to 15–20% of untreated or delayed cases 7.
- Large-Vessel Complications: Thoracic and abdominal aortic aneurysms, aortic dissection, and arterial stenoses, requiring lifelong serial imaging surveillance (MRA, CTA, or ultrasound) due to delayed presentation risks 3,7.
- Cerebrovascular Events: Increased long-term risk of transient ischaemic attacks and ischaemic strokes secondary to internal carotid or vertebral artery vasculitis.
- Glucocorticoid Toxicity: Significant cumulative morbidity related to long-term steroid use, including diabetes mellitus, hypertension, osteoporosis with fragility fractures, weight gain, and cataracts.
- Prognosis: Relapses occur in approximately 40–50% of patients during glucocorticoid tapering, necessitating careful clinical monitoring of acute phase reactants and symptom titration 7.
