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Difficulty: HardHematology and Oncology

A 42-year-old man is brought to the emergency department by his husband due to a 2-day history of progressive confusion, fatigue, and fever. The patient had a mild upper respiratory tract infection one week ago but otherwise has no significant past medical history. He takes no medications.

Vital signs are:
Temperature: 38.6°C (101.5°F)
Blood pressure: 142/88 mm Hg
Heart rate: 110/min
Respiratory rate: 18/min
Oxygen saturation: 98% on room air

Physical examination reveals a lethargic man who is oriented to person only. Scleral icterus is present. The skin examination shows widespread pinpoint, non-blanching red macules over the lower extremities and abdomen. There is no nuchal rigidity, and the remainder of the neurologic examination is nonfocal.

Laboratory studies reveal:
Hemoglobin: 7.6 g/dL
Mean corpuscular volume (MCV): 88 fL
Platelets: 18,000/mm³
Leukocytes: 9,200/mm³
Blood urea nitrogen (BUN): 42 mg/dL
Creatinine: 2.3 mg/dL
Total bilirubin: 4.8 mg/dL
Indirect bilirubin: 3.9 mg/dL
Lactate dehydrogenase (LDH): 1,450 U/L
Haptoglobin: 8 mg/dL (Normal: 50–200 mg/dL)
Prothrombin time (PT): 12 seconds
Activated partial thromboplastin time (aPTT): 28 seconds
Direct antiglobulin (Coombs) test: Negative

Peripheral blood smear reveals numerous fragmented red blood cells.

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

  1. A
    Transport the patient to radiology for a non-contrast computed tomography scan of the head
  2. B
    Transfuse one unit of apheresis platelets and closely monitor neurologic status
  3. Initiate plasma exchange therapyAnswer
  4. D
    Administer high-dose intravenous corticosteroids and intravenous immunoglobulin
  5. E
    Obtain blood cultures and initiate empiric vancomycin and cefepime

Answer

The most appropriate next step is to initiate plasma exchange therapy.
The patient's clinical presentation of fever, confusion, and petechiae, combined with laboratory evidence of thrombocytopenia, microangiopathic hemolytic anemia, and acute kidney injury, is highly characteristic of thrombotic thrombocytopenic purpura (TTP). TTP is caused by a severe deficiency of ADAMTS13, a metalloprotease that cleaves large von Willebrand factor (vWF) multimers. The accumulation of these large multimers leads to widespread platelet adhesion and aggregation, forming microthrombi that shear red blood cells and cause end-organ ischemia. Normal coagulation studies distinguish TTP from disseminated intravascular coagulation. The cornerstone of treatment is immediate plasma exchange, which removes the offending autoantibodies against ADAMTS13 and replenishes the missing enzyme.

Step-by-Step Solution

1
Analyze the patient's clinical presentation and vital signs.
The patient has fever, altered mental status, and petechiae, indicating a systemic process with neurologic and hematologic involvement.
To establish the primary clinical problem and assess for potential instability.
2
Evaluate the laboratory findings and peripheral blood smear.
Labs reveal profound thrombocytopenia and a microangiopathic hemolytic anemia (low Hb, high LDH, high indirect bilirubin, low haptoglobin, negative Coombs, and schistocytes). Coagulation studies (PT and aPTT) are normal.
To differentiate between causes of thrombocytopenia and hemolysis, such as TTP, HUS, DIC, or ITP.
3
Synthesize the findings to establish a diagnosis.
The combination of the classic pentad (microangiopathic hemolytic anemia, thrombocytopenia, fever, acute kidney injury, and neurologic changes) strongly supports a diagnosis of Thrombotic Thrombocytopenic Purpura (TTP).
TTP is a medical emergency requiring rapid clinical diagnosis based on the dyad of microangiopathic hemolytic anemia and thrombocytopenia without another apparent cause.
4
Determine the most appropriate immediate management based on the diagnosis.
The immediate, life-saving intervention for TTP is plasma exchange therapy (plasmapheresis).
Plasma exchange removes the ADAMTS13 autoantibodies and replaces the deficient enzyme, halting the formation of microthrombi.

Key Concept

The diagnosis and emergent management of Thrombotic Thrombocytopenic Purpura (TTP) using plasma exchange therapy.
Estimated Time:1m 30s
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Topics

Hematology and Oncology

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