Palpable purpura in leukocytoclastic vasculitis.

Palpable purpura is a clinical finding that represents antigen-antibody deposition along small cutaneous vessels, resulting in extravasation of blood cells into the interstitium. The most common cause of palpable purpura is leukocytoclastic vasculitis, a disease involving cutaneous postcapillary venules. Although often idiopathic, leukocytoclastic vasculitis has been associated with numerous infections, drugs, rheumatic diseases and malignancies.