Spectrum of inflammation activity in small vessels of the subcutaneous biopsy. (A) Cross-section of two vessels with different stages of inflammation; one with endothelial thickening (asterisk) and the second with a mixed perivascular inflammatory infiltrate consisting of lymphocytes, plasma cells, eosinophilic granulocytes, accompanied by apoptotic figures. (B) Small vessel wall with transmural inflammation as described in (A) (arrow: vessel lumen with erythrocytes). (C) Leukocytoclastic vasculitis with karyorrhexis and fibrinoid necrosis in a small vessel wall. (D) Same vessel as in (C) showing the fibrinoid necrosis (orange) in an acid fuchsin orange G stain.