RheumatologyTier 2Disease (DEADMAN)

Vasculitis - immune complex vasculitis

Description

Immune complex-mediated vasculitis is a distinct pathophysiological category from ANCA-associated vasculitis - vessel wall injury results from deposition of circulating antigen-antibody immune complexes (activating complement and recruiting inflammatory cells), rather than direct ANCA-mediated neutrophil activation

Includes several distinct clinical entities: IgA vasculitis (Henoch-Schonlein purpura), cryoglobulinaemic vasculitis, hypocomplementaemic urticarial vasculitis, and vasculitis secondary to an underlying condition producing circulating immune complexes (e.g. hepatitis C-associated cryoglobulinaemic vasculitis)

Circulating immune complexes deposit in small/medium vessel walls -> activate complement (classical pathway) -> recruit neutrophils -> vessel wall inflammation and injury (leukocytoclastic vasculitis on histology - neutrophilic infiltrate with nuclear debris) - a mechanistically distinct process from ANCA vasculitis's direct neutrophil-activation pathway

IgA vasculitis: classic tetrad of palpable purpura (typically lower limbs), arthralgia, abdominal pain, and renal involvement (IgA nephropathy-like); more common in children but occurs in adults with a generally more severe course
Cryoglobulinaemic vasculitis: associated with hepatitis C infection in a substantial proportion of cases, presenting with palpable purpura, arthralgia, and renal/neurological involvement; cryoglobulins (proteins that precipitate in the cold) are detected on specifically-handled blood samples (kept warm during collection/transport, since cryoglobulins can be missed if the sample cools before testing)
Skin biopsy (leukocytoclastic vasculitis pattern) and complement levels (often low, given complement consumption by immune complex deposition) support diagnosis; low complement specifically helps distinguish immune complex-mediated from ANCA-associated vasculitis, which does not typically show complement consumption

Treat any identified underlying cause specifically (e.g. antiviral therapy for hepatitis C-associated cryoglobulinaemic vasculitis - treating the driving infection, alongside immunosuppression for severe/organ-threatening disease)
Corticosteroids +/- additional immunosuppression for significant organ involvement, following similar principles to other vasculitides though the specific regimen is tailored to the underlying cause
IgA vasculitis in adults/children is often self-limited but requires monitoring for renal involvement, which determines whether more significant immunosuppression is needed

Hepatitis C infection (cryoglobulinaemic vasculitis), IgA nephropathy (shares underlying IgA-related pathology with IgA vasculitis), leukocytoclastic vasculitis on skin biopsy

Cryoglobulin sample handling (keeping the sample warm from collection to processing) is a specific, frequently overlooked pre-analytical requirement - a sample allowed to cool before testing can produce a false-negative result even in true cryoglobulinaemic vasculitis

6 more sections, plus exam facts

Premium unlocks every note across every specialty, and the full exam fact library behind it.