A 35-year-old woman is brought to the emergency department by her husband due to progressi… — USMLE Step 2 CK

A $35$ -year-old woman is brought to the emergency department by her husband due to progressive confusion and lethargy that began yesterday. Over the past week, she has complained of profound fatigue, intermittent nausea, and a low-grade fever. She has no significant past medical history and takes no medications. On physical examination, her temperature is $38.1^\circ\text{C}$ ( $100.6^\circ\text{F}$ ), blood pressure is $130/80\text{ mmHg}$ , pulse is $105/\text{min}$ , and respirations are $16/\text{min}$ . She is mildly disoriented to time and place. Examination of her skin reveals diffuse petechiae and purpura over her bilateral lower extremities. Laboratory studies show:

Hemoglobin: $7.8\text{ g/dL}$
Platelet count: $22,000/\text{mm}^3$
Leukocyte count: $7,200/\text{mm}^3$
Blood urea nitrogen: $35\text{ mg/dL}$
Serum creatinine: $2.4\text{ mg/dL}$
Total bilirubin: $3.2\text{ mg/dL}$
Indirect bilirubin: $2.6\text{ mg/dL}$
Lactate dehydrogenase (LDH): $950\text{ U/L}$
Direct antiglobulin (Coombs) test: Negative
Prothrombin time (PT): $12\text{ seconds}$
Activated partial thromboplastin time (aPTT): $30\text{ seconds}$

A peripheral blood smear reveals numerous schistocytes.

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

Plasma exchangeCevap
B
Platelet transfusion
C
Intravenous immunoglobulin and glucocorticoids
D
Hemodialysis
E
Intravenous heparin

Cevap

The most appropriate initial step in management is plasma exchange.

The correct answer is plasma exchange. This patient presents with the classic pentad of Thrombotic Thrombocytopenic Purpura (TTP): fever, neurologic abnormalities (confusion), renal failure (elevated BUN and creatinine), microangiopathic hemolytic anemia (MAHA), and thrombocytopenia. MAHA is confirmed by the low hemoglobin, elevated indirect bilirubin, significantly elevated LDH, and the presence of schistocytes (fragmented red blood cells) on the peripheral blood smear. TTP is most commonly acquired due to the formation of autoantibodies against ADAMTS13, a metalloprotease responsible for cleaving ultra-large von Willebrand factor (vWF) multimers. Without this cleavage, large vWF multimers accumulate, leading to widespread platelet adhesion and the formation of platelet-rich microthrombi in small blood vessels. The immediate and life-saving treatment for TTP is plasma exchange (plasmapheresis), which achieves two goals: it removes the offending anti-ADAMTS13 autoantibodies and replenishes the functional ADAMTS13 enzyme from the donor plasma.

Adım Adım Çözüm

Analyze the clinical presentation and laboratory findings.

The patient has a pentad of thrombocytopenia, microangiopathic hemolytic anemia (schistocytes, high LDH, high indirect bilirubin), acute kidney injury, neurologic changes (confusion), and fever.

Identifying these five classical findings strongly points toward a specific microangiopathic hemolytic anemia.

Differentiate from similar hematologic emergencies.

Normal PT and aPTT rule out Disseminated Intravascular Coagulation (DIC). A negative Coombs test rules out Autoimmune Hemolytic Anemia (AIHA).

Excluding other causes of hemolysis and thrombocytopenia confirms the diagnosis of Thrombotic Thrombocytopenic Purpura (TTP).

Select the optimal initial targeted therapy.

Plasma exchange is selected as the primary intervention.

TTP is typically caused by autoantibodies against the ADAMTS13 metalloprotease. Plasma exchange removes these antibodies and provides functional ADAMTS13 from donor plasma.

Anahtar Kavram

Thrombotic Thrombocytopenic Purpura (TTP) presents with a classic pentad (fever, neurologic symptoms, renal failure, anemia, thrombocytopenia) and requires emergent plasma exchange; platelet transfusions are generally contraindicated.

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Adım Adım Çözüm

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