The most common and well-known entity in this category is Henoch-Schonlein (H-S) purpura. The primary abnormality is necrotizing inflammation of small venules, characterized by infiltration of the vessel wall by segmented neutrophils accompanied by destruction of some neutrophils with release of nuclear fragments (“leukocytoclastic vasculitis”). Immunohistologic methods can demonstrate IgA deposition in the vessel wall […]