**Giant Cell Arteritis** - also known as Temporal Arteritis & Horton's Disease - **Clinical Features:** * New onset (≥50) headache - can be pulse, throbbing, dull - often, intense, temporal * Jaw claudication - pain when chewing * Inflammation of ophthalmic a. - diplopia - vision loss * Angina pectoris * Abdominal pain * Limb claudication * Asymmetric pulses * Vascular bruit, aortic reg., murmur * Features of AAA, TAA, aortic dissection - aortic regurgitation - ischaemia **Pathogenesis:** 1. **Genetic predisposition** - eg. human leukocyte antigen HLA-DR4 2. **Viral Infections** - eg. parvovirus B19 - Preexisting cell inflammation 3. **Endothelial injury** - Cell-mediated immune response - Macrophages 4. **Inflammation** - In adventitia of blood vessels - Macrophages - Giant cells - Granulomatous inflammation 5. **Local Vascular Damage** - Macrophages - Metalloproteinases - Destroy vessel structures - Internal elastic lamina & IEF 6. **Intimal proliferation** - Th1 cells differentiation - Macrophages - IL-1, IL-6, TNF-α - Inflammatory response - Focal granulomatous inflammation **Most commonly affect ECA branches esp. temporal a. as well as aorta & vertebral a.** **Diagnosis** * ↑ESR * ↑CRP * May have norm. or mild thrombocytosis, leukocytosis or normochromic anemia * ↓chem = norm or ↑ALP, transaminases, ↓ albumin * Coags = norm or ↑ fibrinogen **Bx:** gold standard * All ptx suspected to have: - Intima proliferation - Media necrosis - Fragmentation of internal elastic lamina - Mononuclear infiltration of vessel wall with formation of giant cells **Duplex ULS:** * 1st line imaging for all suspected patients - Halo sign: thickening of vessel wall + halo sign - Non-compressible a. → Compression sign - Stenosis & occlusion **Treatment & Management** * Glucocorticoids * Low-dose aspirin therapy