Vasculitis Syndromes

Definition, Etiology, PathogenesisTop

Vasculitides are a heterogeneous group of diseases in which blood vessel walls are damaged due to inflammation. This may result in bleeding and impaired blood flow, eventually leading to ischemia and necrosis of the associated tissues.

Vasculitis syndromes can be divided into infectious vasculitis (caused by direct invasion and proliferation of a pathogen in a vessel wall) and noninfectious vasculitis. According to the current nomenclature (2012), noninfectious vasculitides (Table 1) can be categorized based on type/size of involved vessels, location of organ involvement, and underlying etiology:

1) Type/size of involved vessels: Large-vessel vasculitis, medium-vessel vasculitis, small-vessel vasculitis, and variable-vessel vasculitis.

2) Location of organ involvement: Single-organ vasculitides can be classified based on type of involved organ (eg, isolated aortitis, cutaneous arteritis).

3) Underlying etiology: Some vasculitides are associated with systemic disease (rheumatoid arthritis, sarcoidosis, systemic lupus erythematous) or with another probable etiology. Probable etiologies include malignancy, viral infection (hepatitis B virus, hepatitis C virus, parvovirus B19, HIV), post-bacterial infection (syphilis), or drugs (eg, beta-lactams, macrolides, selective serotonin reuptake inhibitors, anticonvulsants).

The most common type of vasculitis is small-vessel vasculitis, which is usually associated with immune complexes. Medium- and large-vessel vasculitides are less common, although giant cell arteritis is common in the elderly (12-25/100,000). Note that it is always necessary to establish whether vasculitis is primary or secondary (caused by underlying etiology).

Large-vessel vasculitis: Takayasu arteritis and giant cell arteritis. Large vessel vasculitides predominantly involve large arteries, such as the aorta, carotids, temporal artery, and subclavian arteries.

Medium-vessel vasculitis: Polyarteritis nodosa and Kawasaki disease. Medium-vessel vasculitides involve predominantly medium-sized arteries (in particular the main visceral arteries and their branches) but may affect arteries of any size.

Small-vessel vasculitis (Table 1): These vasculitides mainly involve small parenchymal arteries, arterioles, capillaries, and venules. Small-vessel vasculitis can be further divided into antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis and immune-complex vasculitis.

1) ANCA-associated vasculitis (eg, granulomatosis with polyangiitis [GPA], eosinophilic GPA [EGPA] [Churg-Strauss syndrome], microscopic polyangiitis [MPA]): These vasculitides contain few or absent immunoglobulin deposits in vessel walls. They are also often characterized by the presence of antibodies to myeloperoxidase (MPO ANCA, type of perinuclear ANCA [p-ANCA]) or to proteinase 3 (PR3 ANCA, type of cytoplasmic ANCA [c-ANCA]), although ANCA-negative patients are also observed. Both PR3 ANCA and MPO ANCA are detected using the enzyme-linked immunosorbent assay.

2) Immune-complex vasculitis (including anti-glomerular basement membrane disease): Moderate to severe immunoglobulin and/or complement deposition in vessel walls (often coexisting with glomerulonephritis).

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