A 72-year-old woman with a 3-month history of temporal headache, jaw claudication, and visual disturbances is found to have markedly elevated ESR (110 mm/hr) and CRP. Temporal artery biopsy confirms giant cell arteritis. Regarding the pathological features and clinical associations of large-vessel vasculitides, all of the following are characteristic of giant cell arteritis EXCEPT:

Explanation

## Giant Cell Arteritis: Pathology and Clinical Features ### Diagnostic Criteria and Pathological Hallmarks **Key Point:** Giant cell arteritis (temporal arteritis) is a **large-vessel granulomatous vasculitis** of elastic arteries. The correct diagnosis is based on **clinical presentation + elevated inflammatory markers + temporal artery biopsy**, NOT ANCA serology. ### Pathological Features of GCA | Feature | Characteristic | Diagnostic Significance | |---------|-----------------|------------------------| | **Vessel type** | Elastic arteries (temporal, aorta, carotid, vertebral) | Large-vessel vasculitis | | **Inflammation pattern** | Granulomatous (epithelioid cells, giant cells) | Hallmark finding | | **Layer involvement** | Media and intima | Transmural | | **Internal elastic lamina** | Fragmentation and destruction | Pathognomonic | | **ANCA serology** | Typically NEGATIVE | Not part of diagnostic criteria | ### Why ANCA is NOT Positive in GCA **High-Yield:** Giant cell arteritis is **ANCA-negative**. ANCA positivity is characteristic of: - **c-ANCA (anti-PR3):** Granulomatosis with polyangiitis (GPA, formerly Wegener's) - **p-ANCA (anti-MPO):** Microscopic polyangiitis (MPA), eosinophilic granulomatosis with polyangiitis (EGPA) GCA is diagnosed by **clinical presentation + ESR/CRP elevation + temporal artery biopsy**, not serology. ### Clinical Associations of GCA **Mnemonic:** **THROBBING** = **T**emporal headache + **H**aw claudication + **R**etinal symptoms + **O**lder age (>50) + **B**ranch vessel involvement + **B**imodal ESR + **I**nternal elastic lamina fragmentation + **N**egative ANCA + **G**ranulomatous inflammation ### Polymyalgia Rheumatica (PMR) Association **Clinical Pearl:** 40–60% of GCA patients have concurrent PMR (shoulder and hip girdle pain and stiffness). Conversely, 10–15% of PMR patients develop GCA. Both respond dramatically to corticosteroids. ### Temporal Artery Biopsy 1. **Gold standard** for diagnosis 2. Shows granulomatous inflammation with giant cells 3. Fragmentation of internal elastic lamina (pathognomonic) 4. Sensitivity ~90% if adequate length (>1 cm) and bilateral sampling considered 5. Should be performed **within 1–2 weeks** of clinical suspicion; corticosteroids do not eliminate biopsy findings if given beforehand ### Aortic Involvement **Warning:** Up to 15% of GCA patients develop **aortic arch syndrome** with involvement of the aorta and its major branches (subclavian, carotid, vertebral arteries), leading to: - Aortic regurgitation - Aortic dissection or rupture - Limb claudication - Stroke [cite:Robbins 10e Ch 11; Harrison 21e Ch 297]