Predominantly small-vessel vasculitis

Predominantly small-vessel vasculitis is a group of rare inflammatory disorders characterized by inflammation and destruction of small blood vessels, including arterioles, capillaries, and venules. This category encompasses several distinct conditions, most notably the ANCA-associated vasculitides (granulomatosis with polyangiitis, microscopic polyangiitis, and eosinophilic granulomatosis with polyangiitis) as well as immune complex-mediated small-vessel vasculitides (such as IgA vasculitis/Henoch-Schönlein purpura, cryoglobulinemic vasculitis, and anti-glomerular basement membrane disease). These conditions can affect multiple organ systems, with the kidneys, lungs, skin, and peripheral nerves being most commonly involved. Key clinical features vary depending on the specific subtype but frequently include palpable purpura (a characteristic skin rash caused by bleeding from inflamed small vessels), glomerulonephritis (kidney inflammation that can lead to renal failure), pulmonary hemorrhage, peripheral neuropathy, arthralgia, and constitutional symptoms such as fever, fatigue, and weight loss. Kidney involvement is a particularly serious complication, as it can progress to end-stage renal disease if untreated. Treatment typically involves immunosuppressive therapy tailored to disease severity and subtype. Induction therapy often includes high-dose corticosteroids combined with cyclophosphamide or rituximab, followed by maintenance therapy with agents such as azathioprine, methotrexate, or rituximab. Plasma exchange may be used in severe cases with rapidly progressive glomerulonephritis or pulmonary hemorrhage. Early diagnosis and treatment are critical to preventing irreversible organ damage. Long-term monitoring is essential, as relapses are common in many subtypes.

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