A 58-year-old man presents with sudden-onset severe headache, jaw claudication, and visual loss. Temporal artery biopsy shows granulomatous inflammation. Which clinical feature best distinguishes this condition from polyarteritis nodosa?

Explanation

## Distinguishing Giant Cell Arteritis from Polyarteritis Nodosa **Key Point:** Giant cell arteritis (GCA) is a large-vessel vasculitis affecting the aorta and its proximal branches (carotid, temporal, vertebral arteries), while polyarteritis nodosa (PAN) is a medium-vessel vasculitis sparing the lungs and glomeruli. ### Comparative Features | Feature | Giant Cell Arteritis | Polyarteritis Nodosa | |---------|---------------------|---------------------| | **Vessel caliber** | Large elastic arteries | Medium muscular arteries | | **Organs affected** | Temporal, carotid, vertebral, aorta | Coronary, mesenteric, renal, testicular | | **Glomerulonephritis** | Absent | Absent (distinguishes from ANCA vasculitis) | | **Visceral involvement** | Rare | Common (GI, cardiac, renal) | | **ESR/CRP** | Markedly elevated | Elevated but variable | | **Biopsy finding** | Granulomatous with giant cells | Necrotizing without granulomas | | **Age group** | >50 years | 40–60 years | | **Systemic symptoms** | Fever, malaise, weight loss | Fever, weight loss, organ-specific symptoms | **High-Yield:** GCA spares visceral organs and glomeruli; PAN classically involves mesenteric and coronary arteries, causing MI, GI ischemia, and testicular infarction. ### Why This Distinction Matters **Clinical Pearl:** The **absence of renal involvement and visceral ischemia** in GCA is the cardinal discriminator. PAN patients often present with acute coronary syndrome, mesenteric ischemia, or testicular pain—GCA does not. **Mnemonic:** GCA = **G**reat vessels (aorta, carotid, temporal); PAN = **P**eripheral organs (gut, heart, testes). ### Pathology Correlation GCA shows: - Granulomatous inflammation with giant cells in the media and intima - Fragmentation of the internal elastic lamina - Predominantly affects large elastic arteries PAN shows: - Necrotizing inflammation (fibrinoid necrosis) of the media - **No granulomas** - Segmental involvement of medium muscular arteries - Spares glomeruli and pulmonary vessels **Warning:** Both can present with constitutional symptoms and elevated inflammatory markers—do not confuse them on that basis alone. The organ involvement pattern is the key.