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Difficulty: MediumHematology and Oncology

A 34-year-old woman is brought to the emergency department by her partner due to worsening confusion and lethargy over the past 48 hours. She has also complained of generalized weakness and passing dark urine. Her medical history is unremarkable, and she takes no medications. Her temperature is 38.2°C (100.8°F), blood pressure is 142/88 mmHg, pulse is 105/min, and respirations are 18/min. Physical examination reveals a drowsy but rousable patient who is oriented only to person. Pale conjunctivae and scattered petechiae are noted on the lower extremities. There are no focal motor or sensory deficits.

Laboratory studies show the following:

Laboratory TestResult
Hemoglobin7.4 g/dL
Platelets22,000/mm³
Leukocytes9,400/mm³
Creatinine2.1 mg/dL
Total bilirubin3.5 mg/dL
Indirect bilirubin2.9 mg/dL
Lactate dehydrogenase1,250 U/L
Prothrombin time11.5 sec
Partial thromboplastin time28 sec

A peripheral blood smear demonstrates numerous fragmented red blood cells. Which of the following is the most appropriate next step in the management of this patient?

  1. Perform therapeutic plasma exchangeAnswer
  2. B
    Commence empiric antimicrobial therapy
  3. C
    Administer intravenous sodium bicarbonate
  4. D
    Measure serum thyroid-stimulating hormone
  5. E
    Withhold intervention pending proxy consent

Answer

The most appropriate next step is to perform therapeutic plasma exchange.
The correct answer is therapeutic plasma exchange. This patient presents with the full classic pentad of thrombotic thrombocytopenic purpura (TTP). TTP is caused by decreased activity of the von Willebrand factor (vWF)-cleaving protease ADAMTS13, leading to widespread platelet-rich microthrombi in small vessels. This causes red blood cell shearing (schistocytes, elevated LDH, indirect hyperbilirubinemia) and end-organ damage (renal failure, neurologic symptoms). Therapeutic plasma exchange (plasmapheresis) must be initiated immediately upon suspicion, as it removes the offending autoantibodies and replenishes the deficient ADAMTS13 enzyme.

Step-by-Step Solution

1
Analyze the clinical presentation and laboratory findings.
The patient has fever, altered mental status, acute kidney injury, profound thrombocytopenia, and evidence of microangiopathic hemolytic anemia (elevated LDH, indirect hyperbilirubinemia, and schistocytes).
Identifying these constellation of findings is necessary to recognize the classic pentad of thrombotic thrombocytopenic purpura (TTP).
2
Differentiate the diagnosis from other coagulopathies like DIC.
The prothrombin time (PT) and partial thromboplastin time (PTT) are normal.
Normal coagulation times rule out Disseminated Intravascular Coagulation (DIC), confirming a primary platelet consumption disorder such as TTP.
3
Determine the definitive initial management for TTP.
Therapeutic plasma exchange is selected.
TTP is caused by a severe deficiency of ADAMTS13 (usually due to an acquired autoantibody), leading to uncleaved ultra-large von Willebrand factor multimers and widespread microthrombi. Plasma exchange is the standard of care as it removes the autoantibodies and replaces the missing ADAMTS13 enzyme.

Key Concept

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening microvascular disorder characterized by the pentad of microangiopathic hemolytic anemia, thrombocytopenia, neurologic manifestations, renal failure, and fever. The most critical next step in management is therapeutic plasma exchange.
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Topics

Hematology and Oncology

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