Infectious vasculitis and aortitis
- Lesion
Some microbes attack the vessel wall directly. The vessel thromboses, dies or balloons into an infected aneurysm.
What it is
Infectious vasculitis results from direct invasion of the vessel wall by microbes. Angioinvasive fungi (Aspergillus, Mucorales) grow through vessel walls in immunocompromised people and cause thrombosis and infarction. Rickettsiae infect endothelial cells and cause a widespread small-vessel vasculitis with rash. Bacteria seeded from endocarditis or bacteremia weaken arterial walls into mycotic aneurysms. Tertiary syphilis causes an obliterative endarteritis of the vasa vasorum that leads to aortitis and aneurysm of the ascending aorta.
Structure
- Fungal angioinvasion: broad, ribbon-like aseptate hyphae (Mucorales) or narrow septate hyphae branching at acute angles (Aspergillus) in vessel walls with thrombosis.
- Syphilitic aortitis: concentric thickening of vasa vasorum with plasma-cell cuffs; scarring of the media; wrinkled intima.
- Mycotic aneurysm: necrotic wall with neutrophils and organisms; often saccular.
Clinical notes
- Mycotic aneurysms tend to rupture; they appear in odd places (cerebral, mesenteric) after endocarditis.
- Syphilitic aortic disease is now rare but still appears where syphilis is common.
Test yourself
Think of the answer, then tap the question to see it.
Which fungi typically invade vessel walls?
Aspergillus and the Mucorales (Rhizopus, Mucor), especially in diabetic ketoacidosis, neutropenia or transplant recipients.
Why does syphilis damage the ascending aorta?
It causes obliterative endarteritis of the vasa vasorum, so the media becomes ischemic, scars and dilates.
What is the usual source of a mycotic aneurysm?
Septic emboli from infective endocarditis or seeding of the wall during bacteremia.
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Aortic Aneurysm | MedlinePlus (MedlinePlus, US National Library of Medicine, 2025); Infective Endocarditis (StatPearls (NCBI Bookshelf), 2025).
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Representative model, for educational purposes only.