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Immune Complex Mediated Small Vessel Vasculitides
What are the IC-mediated SVV?
SVV includes a variety of conditions that are grouped together because of the involvement of small blood vessels (<50 μm in diameter) of the skin (arterioles, capillaries, and postcapillary venules). LCV and necrotizing vasculitis are terms used to describe the usual histopathology, in which small blood vessels are infiltrated with polymorphonuclear neutrophils (PMNs) and/or mononuclear cells. As the process evolves, fibrinoid necrosis of the vessel wall with leukocyte fragments (leukocytoclasis) and destruction of the blood vessel wall are seen. Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis is also SVV, but because of the differing clinical presentation and pathologic findings (pauci-immune), it is not included among the family of IC-mediated SVV. Conditions associated with SVV due to IC deposition include those listed in the below table.
Conditions Associated with Small Vessel Vasculitis Due to Immune Complex Deposition
| Condition | Comments |
|---|---|
| Hypersensitivity vasculitis | Most commonly idiopathic or secondary to drug reaction |
| Urticarial vasculitis | If hypocomplementemic consider HUVS and SLE |
| IgA vasculitis (Henoch–Schönlein purpura) | Renal and gastrointestinal involvement common in addition to skin; IgA in vessel walls |
| Cryoglobulinemic vasculitis | Hepatitis B and C, cancer; rheumatic disease |
| Rheumatic disorders | RA, SLE, Sjögren’s syndrome, Crohn disease |
| Infections | SBE, Neisseria, influenza, mononucleosis, HIV, hepatitis B and C |
| Malignancy | Leukemia, lymphoma, myeloma, solid tumors, myelodysplastic syndromes, hairy cell leukemia |
| Antiglomerular basement membrane disease | Pulmonary–renal syndrome (Goodpasture syndrome); in contrast to other conditions in table, does not commonly include cutaneous manifestations |
| Erythema elevatum diutinum | Occurs over the extensor surfaces of joints (hands, knees) and buttocks; responds to dapsone |
HIV , Human immunodeficiency virus; HUVS , hypocomplementemic urticarial vasculitis syndrome; RA , rheumatoid arthritis; SBE , subacute bacterial endocarditis; SLE , systemic lupus erythematosus.
5 Interesting Facts of Immune Complex Mediated Small Vessel Vasculitides
1. The classic cutaneous finding in small-vessel vasculitis (SVV) is palpable purpura.
2. The most common types of immune complex (IC)-mediated SVV include hypersensitivity vasculitis, Henoch–Schönlein purpura (HSP), and cryoglobulinemic vasculitis.
3. Hypersensitivity vasculitis is most commonly idiopathic or due to a drug or infection.
4. HSP presents with palpable purpura, arthritis, abdominal colic, and renal disease; skin biopsy shows leukocytoclastic vasculitis (LCV) with IgA deposition in vessel walls on direct immunofluorescence.
5. Urticarial lesions lasting longer than 24 to 48 hours and resolving with hyperpigmentation are likely vasculitic.
