A 58-year-old man presents with sudden onset of severe headache, jaw claudication, and visual disturbances. ESR is markedly elevated at 95 mm/hr. Temporal artery palpation reveals a tender, non-pulsatile vessel. Which investigation is most appropriate to confirm the diagnosis?

Explanation

## Diagnosis: Giant Cell (Temporal) Arteritis **Key Point:** Temporal artery biopsy remains the gold standard confirmatory test for giant cell arteritis (GCA), demonstrating granulomatous inflammation with giant cells and intimal proliferation. ### Clinical Presentation The patient presents with classic features of GCA: - Temporal headache (most common symptom) - Jaw claudication (pathognomonic) - Visual symptoms (risk of irreversible blindness) - Markedly elevated ESR (typically >50 mm/hr) - Tender temporal artery on examination ### Why Temporal Artery Biopsy is the Gold Standard | Feature | Temporal Artery Biopsy | Other Investigations | |---------|------------------------|----------------------| | **Sensitivity** | 80–95% (gold standard) | Doppler: 60–80% | | **Specificity** | 100% | Imaging: Non-specific | | **Diagnostic certainty** | Definitive histology | Suggestive only | | **Timing** | Within 1–2 weeks of symptom onset | Can be delayed | | **Clinical impact** | Confirms diagnosis, guides long-term therapy | Guides initial suspicion | **High-Yield:** A positive biopsy showing granulomatous inflammation with giant cells is pathognomonic for GCA. The biopsy should be performed within 1–2 weeks of symptom onset; longer delays reduce sensitivity due to skip lesions and healing. ### Biopsy Findings in GCA 1. Granulomatous inflammation of the media and adventitia 2. Giant cells (often at the internal elastic lamina) 3. Intimal proliferation and luminal narrowing 4. Lymphocytic infiltration **Clinical Pearl:** Treatment with corticosteroids should NOT be delayed while awaiting biopsy if clinical suspicion is high and vision is threatened. Biopsy can be performed even after initiation of therapy, as histological changes persist for weeks. **Warning:** Do not confuse GCA with polymyalgia rheumatica (PMR). While PMR often accompanies GCA (10–15% of PMR cases), PMR alone does not require biopsy — it is a clinical diagnosis based on elevated ESR and response to low-dose corticosteroids.