Figure. Histopathologic and immunohistochemical labelings of spleen and skin tissue samples. Tissue samples were fixed in 10% formalin, paraffin-embedded, and examined after hematoxylin-eosin staining, Gimenez staining, or immunostaining with the R47 anti-Rickettsia conorii polyclonal rabbit antibody. The spleen red pulp indicated congestion and ill-defined nodules varying in size and comprising macrophages, polymorphonuclear neutrophils, and necrotic cells (A, magnification ×100). A diffuse macrophage infiltration with abundant hemophagocytosis (not shown) and venulitis (B, magnification ×50) was also observed. In the skin, leukocytoclastic vasculitis with focal vascular necrosis and nonocclusive luminal thrombi were noted in dermal capillaries (C, magnification ×100). Intracellular images evocative of rickettsiae were observed in the splenic arteriolar endothelium upon immunohistochemical staining (D, arrow, magnification ×200; magnified view shown in E, arrowhead, magnification ×500). No infected cells were observed in nodular inflammatory splenic lesions. Immunohistochemical staining also disclosed intracellular immunolabeled dots in cells that could correspond to infected dermal macrophages (F, arrowhead, magnification ×300; magnified view shown in inset, magnification ×600), at a distance from the vascular alterations. Endothelial cells of dermal capillaries were also immunolabeled (Appendix Figure).