Contrasting vascular phenotypes of fatal Bothrops envenoming: Hemorrhagic (Bothrops atrox) versus thrombotic (Bothrops lanceolatus)

Background Envenomation by Bothrops species produces mainly consumption coagulopathy and hemorrhage, and exceptionally thrombosis which is characteristic of few species. These vascular complications are driven by distinct venom toxin repertoires. In the Neotropics, Bothrops atrox typically induces hemorrhagic vasculopathy through SVMP‑mediated endothelial disruption and venom‑induced consumptive coagulopathy (VICC), whereas Bothrops lanceolatus triggers a probable thromboinflammatory syndrome characterized by diffuse arterial and venous thromboses. Comparative clinical descriptions of these divergent vascular phenotypes remain scarce. Methodology and principal findings We report two fatal events illustrating the contrasting vascular tropisms of these species. A patient bitten by B. atrox in French Guiana developed profound VICC, followed by massive intracerebral hemorrhage. Histopathology revealed SVMP-compatible endothelial disruption with perivascular erythrocyte extravasation. In Martinique, a patient bitten by B. lanceolatus presented early coagulation disorders, multifocal cerebral infarctions, myocardial ischemia, and multiorgan failure. Thrombus‑formation kinetics (T‑TAS) showed a time-dependent impairment of thrombus formation. These cases highlight the species‑specific vascular signatures of Bothrops envenoming: SVMP‑driven hemorrhagic vasculopathy for B. atrox and probable immunothrombotic vasculopathy for B. lanceolatus . Delayed presentation contributed to irreversible vascular injury in both patients. Advanced imaging, coagulation phenotyping, and histopathology are essential for delineating the underlying mechanisms involved. Conclusions These two fatal cases illustrate a distinct pathophysiological profile of B. lanceolatus envenoming, characterized by thrombotic complications, contrasting with the predominantly hemorrhagic phenotype typically observed in Bothrops envenoming. Early antivenom administration is critical to prevent catastrophic complications.