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Difficulty: HardHematology and Oncology

A 34-year-old woman is brought to the emergency department by her husband due to progressive confusion and severe fatigue over the past 48 hours. She also complains of a new-onset rash on her lower extremities. She has no significant past medical history and takes no medications. Temperature is 38.1°C (100.6°F), blood pressure is 142/85 mm Hg, pulse is 110/min, and respiratory rate is 18/min. Physical examination reveals mild scleral icterus and pale conjunctivae. There are numerous pinpoint, non-blanching red macules over both lower extremities. Neurological examination is notable for mild disorientation to time and place, but no focal motor or sensory deficits are present.

Laboratory results are as follows:

Laboratory TestResultReference Range
Hemoglobin7.6 g/dL12.0-15.5 g/dL
Platelets18,000/mm³150,000-400,000/mm³
Leukocytes8,400/mm³4,500-11,000/mm³
Creatinine1.6 mg/dL0.6-1.1 mg/dL
Total bilirubin3.8 mg/dL0.1-1.2 mg/dL
Indirect bilirubin3.2 mg/dL0.1-0.8 mg/dL
Lactate dehydrogenase (LDH)1,150 U/L100-250 U/L
Prothrombin time (PT)11.5 sec11-15 sec
Activated partial thromboplastin time (aPTT)28 sec25-40 sec
Fibrinogen350 mg/dL150-400 mg/dL

A peripheral blood smear demonstrates numerous fragmented red blood cells.

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

  1. Plasma exchangeAnswer
  2. B
    Platelet transfusion
  3. C
    Intravenous cefepime and vancomycin
  4. D
    Fresh frozen plasma and cryoprecipitate
  5. E
    Intravenous immunoglobulin and dexamethasone

Answer

Plasma exchange is the most appropriate next step in management.
The correct answer addresses the underlying pathophysiology of Thrombotic Thrombocytopenic Purpura (TTP). The patient exhibits the classic pentad of TTP: microangiopathic hemolytic anemia (schistocytes, elevated LDH, indirect hyperbilirubinemia, anemia), thrombocytopenia, fever, acute kidney injury, and neurologic abnormalities (confusion). A presumptive diagnosis requires only the presence of MAHA and thrombocytopenia without another clear cause. TTP is typically caused by an acquired autoantibody against ADAMTS13, a metalloprotease that cleaves von Willebrand factor (vWF). Without it, ultra-large vWF multimers accumulate, causing systemic platelet trapping and microvascular thrombosis. Immediate plasma exchange (plasmapheresis) is the treatment of choice; it removes the autoantibodies and replenishes the deficient ADAMTS13 enzyme.

Step-by-Step Solution

1
Analyze the patient's clinical presentation.
A young woman presents with acute confusion, severe fatigue, fever, and a petechial rash.
Establishing the initial constellation of symptoms helps frame the differential diagnosis for an acutely ill patient with bleeding signs.
2
Evaluate the laboratory findings and peripheral smear.
Labs show severe thrombocytopenia, hemolytic anemia (elevated indirect bilirubin and LDH), acute kidney injury, and schistocytes. Coagulation studies (PT, aPTT, fibrinogen) are normal.
Differentiating between causes of microangiopathic hemolytic anemia (MAHA) and thrombocytopenia is crucial for determining management.
3
Synthesize the findings to establish a diagnosis.
The combination of MAHA, thrombocytopenia, fever, renal dysfunction, and neurologic changes (classic pentad), along with normal coagulation, confirms Thrombotic Thrombocytopenic Purpura (TTP).
TTP is caused by a severe deficiency in the ADAMTS13 enzyme, leading to unchecked platelet aggregation on ultra-large von Willebrand factor multimers.
4
Determine the most appropriate intervention.
Immediate plasma exchange must be initiated.
Plasma exchange removes the offending autoantibody and provides functional ADAMTS13 enzyme, significantly reducing the high mortality rate associated with untreated TTP.

Key Concept

Diagnosis and emergent management of thrombotic thrombocytopenic purpura (TTP) using plasma exchange.
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Topics

Hematology and Oncology

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