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Difficulty: Very hardHematology and Oncology

A 68-year-old woman is evaluated in the hospital for new-onset skin lesions. Six days ago, she was admitted for a right lower extremity deep vein thrombosis and started on a continuous intravenous unfractionated heparin infusion and oral warfarin. Two days ago, her platelet count was noted to have decreased from 260,000/mm3260,000/\text{mm}^3 on admission to 105,000/mm3105,000/\text{mm}^3. Heparin was immediately discontinued, a serotonin release assay was sent, and an intravenous argatroban infusion was started. Warfarin was continued. Today, she complains of significant pain over her abdomen and both thighs. Physical examination reveals well-demarcated, erythematous, and purpuric lesions with central areas of black necrosis in these regions. Vital signs are stable.

Laboratory results today:
Hemoglobin: 11.2 g/dL11.2\text{ g/dL}
Platelet count: 110,000/mm3110,000/\text{mm}^3
Prothrombin time (PT): 25 sec25\text{ sec}
Activated partial thromboplastin time (aPTT): 68 sec68\text{ sec}
INR: 2.42.4

Which of the following is the most appropriate next step in management?

  1. Discontinue warfarin and administer intravenous vitamin KAnswer
  2. B
    Continue current therapy and provide local wound care
  3. C
    Discontinue argatroban and initiate fondaparinux
  4. D
    Discontinue all anticoagulation and place an inferior vena cava filter
  5. E
    Administer intravenous methylprednisolone and diphenhydramine

Answer

Discontinue warfarin and administer intravenous vitamin K
This patient's clinical presentation—well-demarcated, purpuric lesions progressing to black necrosis on the abdomen and thighs—is classic for warfarin-induced skin necrosis. This rare but serious complication typically occurs 3 to 5 days after initiating warfarin. It results from the rapid depletion of protein C, a vitamin K-dependent natural anticoagulant with a short half-life (approximately 8 hours), which declines significantly faster than the procoagulant factors II, IX, and X. This mismatch creates a transient, severe hypercoagulable state leading to microvascular thrombosis in subcutaneous fat. The risk is significantly magnified in patients with an underlying hypercoagulable state, particularly heparin-induced thrombocytopenia (HIT). In patients with HIT, warfarin is strictly contraindicated until the platelet count has fully recovered (typically >150,000/mm3150,000/\text{mm}^3) because the combination of HIT-associated thrombosis and warfarin-induced protein C depletion can lead to catastrophic venous limb gangrene or skin necrosis. The most appropriate next step is to immediately discontinue the offending agent (warfarin), administer intravenous vitamin K to replenish protein C and reverse the hypercoagulable state, and continue a non-heparin anticoagulant (such as argatroban) to treat the underlying HIT and DVT.

Step-by-Step Solution

1
Analyze the patient's primary diagnosis based on the initial presentation and hospital course.
The patient developed a drop in platelets (>50%) after starting heparin, which is highly suspicious for heparin-induced thrombocytopenia (HIT). This was appropriately treated by stopping heparin and starting argatroban.
Establishing the underlying hypercoagulable state is crucial for understanding subsequent complications.
2
Evaluate the new-onset skin findings in the context of her medications.
The patient developed purpuric, necrotic skin lesions on her abdomen and thighs on day 6 of warfarin therapy. This is the classic presentation of warfarin-induced skin necrosis.
Identifying the etiology of the skin lesions determines the appropriate life-saving intervention.
3
Determine the optimal management for warfarin-induced skin necrosis in a patient with HIT.
Warfarin must be discontinued immediately. Intravenous vitamin K is administered to rapidly reverse the transient protein C depletion, while argatroban is continued to manage the HIT and underlying DVT.
Removing the offending agent and reversing its mechanism is the definitive treatment, while continuous non-heparin anticoagulation prevents systemic thrombosis.

Key Concept

Warfarin-induced skin necrosis in Heparin-Induced Thrombocytopenia (HIT)
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Topics

Hematology and Oncology

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