Giant Cell Arteritis (GCA)

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | Patient Advice

Definition

Giant Cell Arteritis (GCA), also known as temporal arteritis, is a chronic vasculitis affecting large- and medium-sized arteries, primarily the extracranial branches of the carotid artery. It is a medical emergency due to the risk of vision loss.

Aetiology

The exact cause of GCA is unknown, but it is thought to involve an immune-mediated process triggered by environmental and genetic factors.

• Autoimmune Response: Abnormal immune activation targeting arterial walls.
• Genetic Factors: Association with HLA-DRB1*04 alleles.
• Infections: Potential role of infections as a trigger in genetically susceptible individuals.

Pathophysiology

GCA occurs due to an inflammatory response in the arterial walls:

• Immune Activation: Dendritic cells activate T-cells and macrophages, leading to granulomatous inflammation.
• Vascular Damage: Inflammation causes thickening of the intima, narrowing the lumen, and reducing blood flow.
• Complications: Ischaemia can result in symptoms such as headache, jaw claudication, and vision loss.

Risk Factors

Key risk factors include:

• Age >50 years (most commonly affects individuals >70).
• Female sex (2:1 ratio compared to males).
• European ancestry.
• History of polymyalgia rheumatica (PMR).
• Family history of GCA or other autoimmune conditions.

Signs and Symptoms

Typical features of GCA include:

• Headache: Severe, localised, and often unilateral over the temples.
• Scalp Tenderness: Pain when combing hair or touching the scalp.
• Jaw Claudication: Pain or fatigue in the jaw muscles while chewing.
• Visual Symptoms: Blurred vision, diplopia, or sudden vision loss (ocular emergency).
• Systemic Symptoms: Fatigue, fever, weight loss, and night sweats.

Investigations

Key investigations and expected findings include:

• Clinical Examination: Tender, thickened temporal artery with reduced or absent pulsation.
• Blood Tests:
  • Erythrocyte Sedimentation Rate (ESR): Typically >50 mm/hr.
  • C-reactive Protein (CRP): Markedly elevated due to inflammation.
  • Full Blood Count (FBC): May show normocytic anaemia or thrombocytosis.
• Temporal Artery Biopsy (TAB): Gold standard for diagnosis. Positive findings include granulomatous inflammation with multinucleated giant cells.
• Imaging:
  • Ultrasound: Halo sign indicating arterial wall inflammation.
  • MRI/CT Angiography: To assess large-vessel involvement in atypical cases.

Management

1. Acute Management

• Glucocorticoids: Start immediately if GCA is suspected to prevent vision loss.
  • High-dose prednisolone (40–60 mg daily) for uncomplicated GCA.
  • Intravenous methylprednisolone (1 g daily for 3 days) for visual symptoms or other complications.
• Proton Pump Inhibitors (PPIs): To reduce the risk of gastric side effects from steroids.
• Aspirin: Low-dose (75 mg daily) to reduce the risk of vascular events.

2. Long-term Management

• Tapering Steroids: Gradual dose reduction over 12–18 months to minimise relapse risk.
• Immunosuppressants: Methotrexate or tocilizumab may be added in refractory or steroid-dependent cases.
• Bone Protection: Calcium, vitamin D, and bisphosphonates to prevent steroid-induced osteoporosis.

3. Specialist Referral

Referral to a rheumatologist is essential for diagnosis confirmation and long-term management. Ophthalmology referral is required for visual symptoms or suspected ocular involvement.

Patient Advice

Key advice includes:

• Adhere to prescribed steroid treatment and attend regular follow-ups.
• Report new symptoms, particularly visual changes or severe headaches, immediately.
• Maintain a healthy diet and engage in weight-bearing exercise to reduce the risk of osteoporosis.
• Take vitamin D and calcium supplements as recommended.