Immune complex mediated vasculitis

Immune complex mediated vasculitis is a group of inflammatory vascular disorders in which circulating immune complexes (composed of antigens bound to antibodies) deposit in blood vessel walls, triggering complement activation and an inflammatory response that damages the vessels. This category encompasses several specific conditions, including IgA vasculitis (formerly Henoch-Schönlein purpura), cryoglobulinemic vasculitis, hypocomplementemic urticarial vasculitis, and vasculitis associated with serum sickness or infections. The immune complex deposition predominantly affects small vessels, including arterioles, capillaries, and venules, though medium-sized vessels may also be involved depending on the specific subtype. The clinical manifestations vary depending on which organs are affected but commonly include palpable purpura (raised, non-blanching skin lesions), joint pain and swelling (arthralgia/arthritis), kidney involvement (glomerulonephritis with hematuria and proteinuria), and gastrointestinal symptoms such as abdominal pain and bleeding. Peripheral neuropathy, particularly mononeuritis multiplex, may also occur. Systemic symptoms including fever, fatigue, and malaise are frequently present. The severity ranges from mild, self-limited skin disease to life-threatening multi-organ involvement. Treatment depends on the underlying cause and severity of the disease. Identifying and addressing the triggering antigen (such as an infection or medication) is a key first step. Mild cases may be managed with supportive care and nonsteroidal anti-inflammatory drugs. More severe or organ-threatening disease typically requires immunosuppressive therapy, including corticosteroids, and in refractory cases, agents such as cyclophosphamide, azathioprine, mycophenolate mofetil, or rituximab. Plasmapheresis may be employed in severe cryoglobulinemic vasculitis or rapidly progressive disease to remove circulating immune complexes.

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