Hypersensitivity vasculitis

Hypersensitivity vasculitis most commonly involves 

A. Arterioles
B. Post capillary venules
C. Capillaries
D. Medium sized arteries

Ans. B.  Post capillary venules 

Vasculitis of Small Vessels 

Hypersensitivity vasculitis primarily affects postcapillary venules and arterioles of the skin. 

This disorder usually presents as palpable purpura, although lesions may occasionally be urticarial or ulcerative. 

Skin biopsy usually shows leukocytoclastic angiitis. 

> Small-vessel vasculitis may also be associated with visceral involvement, including alveolar hemorrhage or glomerulonephritis. 

Visceral involvement most commonly occurs in Henoch-Schönlein purpura, cryoglobulinemia and vasculitis associated with autoimmune diseases, such as SLE.