Developments in large and midsize vasculitis.

Childhood vasculitis is a complex and fascinating area in pediatric rheumatology that has experienced an unprecedented surge in research, leading to new knowledge over the past several years. Vasculitis is defined as the presence of inflammatory cell infiltration in blood vessel walls, usually with multisystemic involvement. The most frequent forms of vasculitis in childhood are the small-size vasculitides, of which Henoch-Schoenlein Purpura and other leucocytoclastic vasculitis are the best examples, followed by Kawasaki disease, a midsize vasculitis, and Takayasu arteritis, a large-size vasculitis, both of which are topics in this article.