Vasculitis - classification, etiology, pathogenesis, and clinical manifestations.
Vasculitis is inflammation and necrosis of blood vessel walls, affecting arteries, veins, or capillaries, leading to vessel wall damage and ischemia of supplied tissues.
Classification
By vessel size (Chapel Hill classification)
Etiology
- 1 Primary (idiopathic/ autoimmune)
Unknown trigger, often immune- mediated.
Associated with ANCA (antineutrophil cytoplasmic antibodies) in some forms.
- 2 Secondary
Infections: hepatitis B and C (especially PAN), bacterial infections.
Drugs: hydralazine, propylthiouracil.
Neoplasms: paraneoplastic vasculitis.
Connective tissue diseases: SLE, rheumatoid arthritis.
Pathogenesis
- 1 Immune- mediated mechanisms
Immune complex deposition (e.g., in Henoch- Schönlein purpura, secondary to infections).
ANCA-mediated neutrophil activation (e.g., microscopic polyangiitis, granulomatosis with polyangiitis).
- Activated neutrophils → release of ROS and proteolytic enzymes → vessel wall necrosis (fibrinoid necrosis).
- Endothelial damage and thrombosis → ischemia, infarction of downstream tissues.
- Healing → fibrosis and vessel wall scarring → possible stenosis or aneurysm formation.
Clinical manifestations
General systemic symptoms
Fever, malaise.
Weight loss.
Arthralgias, myalgias.
Organ- specific signs (depending on vessels involved)
Skin
Palpable purpura (small vessel vasculitis hallmark).
Livedo reticularis.
Ulcers.
Kidneys
Hematuria, proteinuria (glomerulonephritis).
Respiratory tract
Sinusitis, nasal crusting (granulomatosis with polyangiitis).
Pulmonary hemorrhage.
Nervous system
Mononeuritis multiplex (asymmetric peripheral neuropathy).
GI tract
Abdominal pain.
GI bleeding (mesenteric ischemia).
Heart
Coronary arteritis (e.g., Kawasaki disease).
Large vessel vasculitis specific
Limb claudication (Takayasu arteritis).
Temporal headache, jaw claudication, visual disturbances (giant cell arteritis).