A 38-year-old woman is brought to the emergency department by her husband due to sudden-on… — USMLE Step 2 CK

A $38$ -year-old woman is brought to the emergency department by her husband due to sudden-onset confusion, agitation, and strange behavior that began this morning. For the past $3$ days, she has complained of profound fatigue, generalized weakness, and subjective fevers. She has no significant past medical history and takes no medications. Her temperature is $38.2^\circ\text{C}$ ( $100.8^\circ\text{F}$ ), pulse is $112\text{/min}$ , blood pressure is $142/88\text{ mmHg}$ , and respiratory rate is $18\text{/min}$ . Physical examination reveals a confused and agitated woman. There are numerous non-blanching, pinpoint erythematous macules on her bilateral lower extremities. Neurological examination reveals no focal motor or sensory deficits, but she is oriented only to person.

Laboratory studies reveal:
Hemoglobin: $7.4\text{ g/dL}$
Platelet count: $22,000/\mu\text{L}$
Leukocyte count: $9,200/\mu\text{L}$
Creatinine: $2.2\text{ mg/dL}$
Total bilirubin: $3.8\text{ mg/dL}$
Indirect bilirubin: $3.1\text{ mg/dL}$
Thyroid-stimulating hormone (TSH): $4.8\text{ }\mu\text{U/mL}$ (Normal: $0.4-4.0\text{ }\mu\text{U/mL}$ )

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?

A
Transfuse pooled donor platelets
B
Administer intravenous ceftriaxone and vancomycin
Initiate therapeutic plasma exchangeAnswer
D
Administer intravenous haloperidol and arrange psychiatric admission
E
Defer interventions until informed consent is obtained from the patient's parents

Answer

The correct answer is to initiate therapeutic plasma exchange.

The correct answer is to initiate therapeutic plasma exchange. This patient presents with the classic pentad of Thrombotic Thrombocytopenic Purpura (TTP): fever, microangiopathic hemolytic anemia (schistocytes, elevated indirect bilirubin, anemia), thrombocytopenia, renal insufficiency (elevated creatinine), and neurologic symptoms (confusion, agitation). TTP is a life-threatening hematologic emergency caused by severe deficiency of the von Willebrand factor (vWF)-cleaving protease ADAMTS13, leading to unchecked platelet aggregation and microvascular thrombosis. Therapeutic plasma exchange (plasmapheresis) is the definitive next step in management as it removes the offending autoantibodies and replenishes functional ADAMTS13.

Step-by-Step Solution

Analyze the patient's clinical presentation and vitals.

38

-year-old woman presents with acute-onset confusion, fever (

38.2^\circ\text{C}

), and petechiae.

To identify the primary organ systems involved (neurologic and dermatologic/hematologic) in an acutely ill patient.

Interpret the laboratory findings and peripheral blood smear.

Labs reveal severe thrombocytopenia (

22,000/\mu\text{L}

), anemia (

7.4\text{ g/dL}

) with elevated indirect bilirubin, acute kidney injury (creatinine

2.2\text{ mg/dL}

), and schistocytes on smear.

To confirm the presence of Microangiopathic Hemolytic Anemia (MAHA) and differentiate it from other causes of thrombocytopenia.

Synthesize findings to establish the most likely diagnosis.

The combination of MAHA, thrombocytopenia, fever, renal dysfunction, and neurologic abnormalities represents the classic pentad of Thrombotic Thrombocytopenic Purpura (TTP).

To select the appropriate life-saving intervention, as TTP requires immediate, specialized treatment.

Determine the best next step in management based on the diagnosis of TTP.

Therapeutic plasma exchange must be initiated immediately.

Plasma exchange removes autoantibodies against ADAMTS13 and provides the functional enzyme, reversing the microvascular thrombosis.

Key Concept

Diagnosis and emergent management of Thrombotic Thrombocytopenic Purpura (TTP) with therapeutic plasma exchange.

Estimated Time:1m 30s

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