Synonyms: Leukocytoclastic vasculitis, Necrotizing vasculi- tis, Allergic vasculitis, Cutaneous allergic vasculitis

Cutaneous small-vessel vasculitis (CSVV) is a general term for diseases that present pathological features of leukocytoclastic vasculitis, i.e., diseases with pathological perivascular neutrophilic infiltration and fibrinoid degeneration of the vascular walls (Fig. 11.1). Henoch-Schönlein purpura and urticarial vasculitis are included under a broad definition of CSVV; however, they are usually treated as distinct diseases. In its more restricted sense, CSVV is considered to be a disease caused by small-vessel vasculitis in the dermis (in and between the middle and deep layers of the dermis).