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Zorluk: OrtaHemodynamic and Coagulation Processes

A 48-year-old woman is admitted to the hospital with a massive left iliofemoral deep vein thrombosis. She is immediately started on an intravenous infusion of unfractionated heparin, and oral warfarin is initiated on the same day. Her past medical history is significant for two prior unprovoked lower extremity deep vein thromboses in her 30s. On hospital day 3, she complains of severe pain over her anterior thighs and abdomen. Physical examination reveals several large, well-demarcated, erythematous plaques that rapidly progress to purpuric, necrotic eschars over the next 12 hours. Laboratory studies show a platelet count of 245,000/mm³ (baseline 250,000/mm³), a prothrombin time (PT) of 22 seconds, and an activated partial thromboplastin time (aPTT) of 65 seconds. Which of the following underlying conditions most strongly predisposed this patient to develop this specific cutaneous complication?

  1. Inherited deficiency of an endogenous anticoagulant factor with a short circulating half-lifeCevap
  2. B
    Production of IgG autoantibodies directed against complexes of a drug and a platelet protein
  3. C
    Resistance of an activated procoagulant factor to proteolytic degradation
  4. D
    Reduced baseline levels of a serine protease inhibitor that complexes with a glycosaminoglycan
  5. E
    Dislodgement of atheromatous debris from the aorta following systemic anticoagulation

Cevap

Inherited deficiency of an endogenous anticoagulant factor with a short circulating half-life
The correct answer identifies an inherited deficiency of Protein C, an endogenous anticoagulant that requires vitamin K for its synthesis. Warfarin works by inhibiting the enzyme vitamin K epoxide reductase, which prevents the gamma-carboxylation of procoagulant factors II, VII, IX, and X, as well as the anticoagulant proteins C and S. Because Protein C has a very short biological half-life (approximately 8 hours) compared to Factor II (approximately 72 hours), initiating warfarin causes Protein C levels to plummet first. This leads to a transient, paradoxical hypercoagulable state. In patients who already have an underlying, inherited Protein C deficiency (which is highly likely in a young patient with multiple unprovoked DVTs), this transient hypercoagulable state is severely exaggerated, leading to diffuse microvascular thrombosis in adipose tissue and subsequent skin necrosis.

Adım Adım Çözüm

1
Analyze the patient's clinical presentation and timeline.
The patient developed painful, purpuric, necrotic eschars on her thighs and abdomen 3 days after starting warfarin and heparin. Her platelet count remains normal.
Establishing the timeline and key physical findings helps differentiate among adverse drug reactions.
2
Identify the specific cutaneous complication.
The clinical picture of rapid-onset skin necrosis in adipose-rich areas shortly after initiating warfarin is diagnostic of warfarin-induced skin necrosis.
Matching the classic physical exam findings with the pharmacologic timeline allows for accurate diagnosis.
3
Determine the pathophysiologic mechanism and predisposing factors.
Warfarin causes a rapid drop in Protein C levels before procoagulant factors are depleted. Patients with an underlying, inherited Protein C deficiency are at the highest risk for this exaggerated transient hypercoagulable state.
The question asks for the underlying condition predisposing the patient to this exact complication, requiring knowledge of coagulation factor half-lives.

Anahtar Kavram

Warfarin-induced skin necrosis typically occurs in patients with an underlying Protein C deficiency due to the rapid, disproportionate depletion of this short-lived anticoagulant, which creates a transient hypercoagulable window.
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Hemodynamic and Coagulation Processes

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