Arteritis and Phlebitis

1. Vasculitis — definition

Vasculitis = arteritis = angiitis: inflammation of the vessel wall. Two broad mechanisms: infectious (direct invasion) and non-infectious / immune-mediated.

2. Infectious vasculitis

Localized inflammation from direct invasion by pathogens — usually bacteria or fungi (Aspergillus, Mucor). Wall weakening → mycotic aneurysm / thrombosis → infarction.

3. Non-infectious (immune-mediated) mechanisms

1. Type III hypersensitivity (immune complexes): circulating complexes deposit in the wall → complement activation → macrophage lysis + PMN invasion → ROS → inflammation (SLE, drug-induced, post-infectious).
2. ANCA: autoantibodies to neutrophil cytoplasmic antigens → neutrophil activation/degranulation → ROS + proteolytic enzymes → endothelial damage. P-ANCA (perinuclear) ↔ polyarteritis nodosa / microscopic polyangiitis; C-ANCA (cytoplasmic) ↔ Wegener.
3. Anti-endothelial antibodies: Kawasaki disease.
4. Cell-mediated: heavy T-cell infiltration.

4. Classification by vessel size

Large vessel	Medium vessel	Small vessel
Giant cell (temporal) arteritis; Takayasu arteritis	Polyarteritis nodosa; Kawasaki; (rheumatoid arthritis, SLE, Churg-Strauss)	Microscopic polyangiitis (leukocytoclastic); Wegener granulomatosis; thromboangiitis obliterans (Buerger); post-infectious

5. Large-vessel vasculitis

• Giant cell (temporal) arteritis: elderly; temporal (also ophthalmic → blindness, vertebral) arteries; chronic granulomatous, segmental inflammation with giant cells + fragmentation of the internal elastic lamina, healing by fibrosis. Headache, visual loss, facial pain; temporal artery biopsy; treat with corticosteroids.
• Takayasu arteritis (“pulseless disease”): women < 50, mostly Asia; fibrosis of the aortic arch narrowing/obliterating the great-vessel origins (intimal thickening, granulomatous inflammation around vasa vasorum). Weak upper-limb pulses, ocular disturbance/retinal hemorrhage → blindness, neurological deficits.

6. Medium-vessel vasculitis

• Polyarteritis nodosa (PAN): poly = many arteries (renal, coronary, hepatic, mesenteric), nodosa = segmental; necrotizing, immune-complex (often post-HBV); spares the pulmonary circulation. Acute = transmural infiltrate + fibrinoid necrosis + thrombosis; chronic = fibrous thickening. Episodic fever, weight loss, hypertension, abdominal/muscle pain; P-ANCA (+); corticosteroids.
• Kawasaki syndrome (mucocutaneous lymph node syndrome): children < 4, endemic in Japan; anti-endothelial antibodies; coronary + mucocutaneous arteries. PAN-like wall changes. Conjunctival/oral erythema, hand-foot edema, palm/sole erythema, desquamative rash, cervical lymphadenopathy; coronary aneurysm → rupture → AMI / SCD.

7. Small-vessel vasculitis

• Microscopic polyangiitis (leukocytoclastic / hypersensitivity): necrotizing vasculitis of arterioles, venules, capillaries; P-ANCA response to tumors/drugs (penicillin)/microbes → neutrophil recruitment; segmental necrosis with fragmented neutrophil nuclei (“leukocytoclasia”). Hemoptysis, hematuria/proteinuria, GI bleeding, muscle pain, purpura.
• Wegener granulomatosis: triad of (1) necrotizing granulomas of upper & lower respiratory tract, (2) necrotizing vasculitis of small/medium vessels, (3) necrotizing glomerulonephritis; cell-mediated hypersensitivity to inhaled agent; C-ANCA (+). Chronic sinusitis, nasopharyngeal ulceration, glomerulonephritis; treat with steroids.
• Thromboangiitis obliterans (Buerger disease): segmental thrombosing inflammation of small arteries (± veins → phlebitis); almost exclusively smokers < 35. Hypersensitivity to tobacco → endothelial injury, vasoconstriction, hypercoagulability. Micro: granulomatous inflammation, microabscesses + luminal thrombosis, later fibrosis. Superficial nodular phlebitis, neural pain, gangrene of extremities → amputation risk.

💡 High-yield: Map vasculitis to vessel size + serology: Giant cell (elderly, temporal artery, blindness, granulomatous, biopsy + steroids) & Takayasu (young Asian women, pulseless arch) = large; PAN (HBV, spares lungs, P-ANCA, renal/coronary) & Kawasaki (kids, coronary aneurysm, anti-endothelial Ab) = medium; Microscopic polyangiitis (P-ANCA, leukocytoclastic), Wegener (C-ANCA, resp + renal triad), Buerger (young male smokers, gangrene) = small.