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.
 
Cardiology, NeurologymypanotesGiant Cell Arteritis (GCA)