A 45-year-old man is hospitalized for the treatment of acute promyelocytic leukemia. Eight… — USMLE Step 2 CK

A 45-year-old man is hospitalized for the treatment of acute promyelocytic leukemia. Eight days ago, he was started on induction therapy with all-trans retinoic acid and arsenic trioxide, along with empiric intravenous cefepime for neutropenic fever. Over the last $24$ hours, his temperature is $38.6^\circ\text{C}$ ( $101.5^\circ\text{F}$ ), blood pressure is $110/70\text{ mm Hg}$ , pulse is $112/\text{min}$ , and respirations are $24/\text{min}$ . Oxygen saturation is $89\%$ on room air. He reports progressive shortness of breath and a nonproductive cough. Physical examination reveals bilateral basilar crackles, $2+$ bilateral lower extremity edema, and elevated jugular venous pressure. Laboratory studies show a leukocyte count of $28,000/\text{mm}^3$ (up from $4,000/\text{mm}^3$ on admission). Chest radiography demonstrates bilateral diffuse interstitial opacities and small bilateral pleural effusions. Which of the following is the most specific and critical next step in the management of this patient's acute respiratory decompensation?

Intravenous dexamethasoneAnswer
B
Intravenous furosemide
C
Addition of intravenous vancomycin
D
Discontinuation of all-trans retinoic acid and arsenic trioxide
E
Immediate leukapheresis

Answer

Intravenous dexamethasone

The correct answer is the immediate administration of intravenous dexamethasone. This patient is presenting with Differentiation Syndrome (formerly known as retinoic acid syndrome), a life-threatening complication of induction therapy with all-trans retinoic acid (ATRA) and arsenic trioxide for acute promyelocytic leukemia (APL). As the malignant promyelocytes are forced to differentiate into mature neutrophils, they release massive amounts of inflammatory cytokines. This results in a systemic inflammatory response syndrome characterized by fever, peripheral edema, weight gain, hypotension, and profound capillary leak leading to pulmonary infiltrates, pleural effusions, and pericardial effusions. The diagnostic hallmark often includes a rapidly rising leukocyte count. The definitive, life-saving therapy is the immediate initiation of high-dose corticosteroids, specifically intravenous dexamethasone, which rapidly blunts the cytokine storm. Importantly, ATRA is typically continued during moderate differentiation syndrome; temporary discontinuation is reserved only for severe cases (e.g., acute respiratory distress syndrome requiring intubation or acute renal failure).

Step-by-Step Solution

Identify the primary diagnosis and current treatment.

The patient has acute promyelocytic leukemia (APL) and is receiving induction therapy with all-trans retinoic acid (ATRA) and arsenic trioxide.

Establishing the current therapeutic context is essential for identifying treatment-specific complications.

Analyze the new clinical presentation and timeline.

Eight days after starting ATRA, the patient developed fever, dyspnea, hypoxemia, weight gain (edema), a rising leukocyte count, and bilateral pulmonary opacities.

This timeline and symptom cluster (fever, pulmonary infiltrates, effusions, expected leukocytosis) are the hallmark signs of a specific adverse drug reaction.

Formulate a diagnosis for the acute decompensation.

The clinical picture perfectly matches Differentiation Syndrome (formerly retinoic acid syndrome), caused by differentiating promyelocytes releasing inflammatory cytokines.

Recognizing the capillary leak nature of this syndrome prevents misdiagnosing it as isolated heart failure or pneumonia.

Select the definitive management for the complication.

The treatment of choice is immediate high-dose intravenous dexamethasone.

Steroids are required to suppress the life-threatening cytokine storm. ATRA is generally continued unless the syndrome is severe (e.g., renal failure, need for intubation).

Key Concept

Differentiation Syndrome in APL

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