The syndromes of purpuric lesions associated with a thrombotic mechanism are very rare in the general population. Dermal vascular thrombosis, however, can be devastating and associated with significant morbidity and mortality. These syndromes share common features in their clinical course, pathogenesis, and histology. Although these syndromes can be initiated by either the hemostatic or inflammatory pathways, both pathways center around perturbations of the endothelial cell, which promote thrombosis. If animal models or better testing can be developed, enhanced appreciation of mechanisms underlying purpura fulminans may be deduced. Characterization of the pathophysiology may then allow directed treatment modalities that could limit the course of these syndromes and reduce morbidity and mortality.