Superwarfarin Poisoning Mimicking a Hematological Disorder: A Case Report of Delayed Diagnosis

Background

Brodifacoum and other second-generation anticoagulant rodenticides, collectively termed “superwarfarins,” inhibit vitamin K epoxide reductase (VKORC1) more potently and for a substantially longer duration than warfarin. A single exposure can produce anticoagulation persisting for weeks to months. Because exposure is frequently unrecognized or undisclosed by the patient, the presenting picture — bleeding associated with an isolated elevation of the prothrombin time (PT) against an otherwise unremarkable blood count — is easily mistaken for a primary hematological disorder and routinely delays correct diagnosis. Case Presentation: A 36-year-old previously healthy office worker presented with several days of spontaneous, gross hematuria, without antecedent trauma, a personal or family bleeding tendency, hepatic disease, or reported anticoagulant use. Complete blood count was unremarkable (hemoglobin 12.7 g/dL; total leukocyte counts 3,700/mm³; platelet count 160 × 10⁹/L; peripheral smear unremarkable), whereas the coagulation screen was disproportionately abnormal (PT 62 seconds; INR 5.8; aPTT 46 seconds). A 1:1 mixing study showed full correction, favoring a factor deficiency over a circulating inhibitor. Factor assays demonstrated reduced activity of factors II, VII, IX, and X (II 18%, VII 8%, IX 22%, X 15%;), with factor V activity preserved at 95% (reference 70–120%). Liver and renal function were normal. On focused re-questioning, the patient disclosed deliberate ingestion of a rodenticide preparation several weeks earlier in a previously undisclosed suicide attempt; a serum brodifacoum assay performed by high-performance liquid chromatography (HPLC) was positive at 210 ng/mL. He was treated with intravenous followed by oral vitamin K1 (phytonadione) and fresh frozen plasma; hematuria recurred after an initial, time-limited course of oral vitamin K1 and resolved only after institution of a prolonged, higher-dose oral vitamin K1 regimen (full dosing and timeline in Table 3).