4.01 Small Vessel Vasculitis

Rheumatology review for the USMLE Step 1 exam

• Vasculitis is inflammation of blood vessels and is classified into three categories based on vessel size: large, medium, and small vessel vasculitis.
• Small vessel vasculitis affects arterioles, capillaries, and venules, leading to symptoms associated with damage to these vessels, such as palpable purpura.
• Five types of small vessel vasculitis include IgA vasculitis (Henoch-Schonlein Purpura), Granulomatosis with polyangiitis (Wegener Granulomatosis), Eosinophilic granulomatosis with polyangiitis (Churg-Strauss syndrome), Microscopic polyangiitis, and Behçet syndrome.
• IgA vasculitis is the most common in children, and anti-neutrophil cytoplasmic antibody + vasculitis are the most common in adults.
• IgA vasculitis is caused by the deposition of IgA immune complexes after an upper respiratory or GI tract infection, leading to palpable purpura, renal, GI, and joint involvement. It resolves on its own in a few weeks, and steroids and NSAIDs are used to reduce severity of symptoms.