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Difficulty: HardHematology and Oncology

A 71-year-old man comes to the clinic due to the sudden onset of extensive bruising over his trunk and arms over the past two weeks. He also reports painful swelling in his right knee that began yesterday after bumping it against a table. He has a history of hypertension and osteoarthritis. He has never had abnormal bleeding before, including during a cholecystectomy 10 years ago. Current medications include lisinopril and acetaminophen. Vital signs are within normal limits. Physical examination reveals large, coalescing ecchymoses over the abdomen and proximal extremities. The right knee is warm, swollen, and tender. Laboratory studies show:

TestResultReference Range
Hemoglobin10.8 g/dL13.5-17.5 g/dL
Platelet count210,000/mm³150,000-400,000/mm³
Prothrombin time (PT)11.2 sec11-15 sec
Activated partial thromboplastin time (aPTT)78 sec25-40 sec

A 1:1 mixing study with normal plasma is performed, and the aPTT remains prolonged at 72 seconds. Which of the following is the most appropriate next step in the management of this patient's bleeding?

  1. Administer recombinant factor VIIaAnswer
  2. B
    Administer factor VIII concentrate
  3. C
    Administer desmopressin (DDAVP)
  4. D
    Transfuse fresh frozen plasma
  5. E
    Administer vitamin K

Answer

Administer recombinant factor VIIa
The correct answer is to administer a bypassing agent such as recombinant factor VIIa. This patient's presentation of spontaneous deep tissue bleeding (hemarthrosis, large coalescing ecchymoses) in the seventh decade of life with no prior personal or family bleeding history is highly suggestive of an acquired bleeding disorder. The laboratory findings show an isolated prolonged activated partial thromboplastin time (aPTT). The critical diagnostic step is the 1:1 mixing study, which fails to correct the aPTT into the normal range. A failure to correct indicates the presence of an inhibitor (an autoantibody) rather than a simple factor deficiency. The most common acquired coagulation inhibitor is directed against factor VIII, leading to acquired hemophilia A. In the setting of acute, severe bleeding in acquired hemophilia A, providing standard factor VIII concentrate is ineffective because the circulating autoantibodies will rapidly neutralize it. Instead, hemostasis must be achieved using bypassing agents, specifically recombinant factor VIIa (rFVIIa) or activated prothrombin complex concentrate (aPCC). These agents bypass the intrinsic pathway defect by directly activating factor X or providing activated downstream factors, thereby enabling thrombin generation and subsequent clot formation.

Step-by-Step Solution

1
Analyze the basic coagulation profile.
The patient has an isolated prolonged aPTT with a normal PT and platelet count.
This localizes the hemostatic defect to the intrinsic coagulation pathway (factors VIII, IX, XI, or XII).
2
Interpret the mixing study results.
The aPTT fails to correct after mixing the patient's plasma 1:1 with normal plasma.
Failure to correct indicates the presence of a circulating coagulation inhibitor (an autoantibody), rather than a simple factor deficiency.
3
Synthesize the clinical presentation with the laboratory findings.
An elderly patient with no prior bleeding history presenting with sudden severe tissue bleeding and an inhibitor to the intrinsic pathway.
This is the classic presentation of acquired hemophilia A, which is caused by autoantibodies directed against factor VIII.
4
Determine the optimal acute management for the bleeding episode.
Bypass the inhibited factor VIII using specific bypassing agents.
Standard factor VIII replacement will be neutralized by the autoantibodies. Recombinant factor VIIa directly activates factor X, bypassing the need for factor VIII and allowing the coagulation cascade to proceed.

Key Concept

Acquired hemophilia A typically presents in older adults with acute, severe bleeding, an isolated prolonged aPTT, and failure of the aPTT to correct on a mixing study. Acute bleeding must be managed with bypassing agents such as recombinant factor VIIa or activated prothrombin complex concentrate.
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Topics

Hematology and Oncology

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