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Difficulty: MediumHematology and Oncology

A 41-year-old woman is evaluated in the emergency department for a 2-day history of severe epistaxis, easy bruising, and profound fatigue. Laboratory studies reveal a hemoglobin of 7.8 g/dL7.8 \text{ g/dL}, a leukocyte count of 1,200/μL1,200/\mu\text{L}, and a platelet count of 18,000/μL18,000/\mu\text{L}. Coagulation studies show a prolonged prothrombin time, a prolonged activated partial thromboplastin time, a significantly elevated D-dimer, and a fibrinogen level of 85 mg/dL85 \text{ mg/dL} (normal: 150−400 mg/dL150-400 \text{ mg/dL}). The patient is suspected to have acute promyelocytic leukemia (APL). Arrange the following diagnostic and therapeutic steps in the most appropriate chronological sequence for managing this patient.

  1. 1Review the peripheral blood smear for atypical promyelocytes with Auer rods.
  2. 2Initiate immediate empiric therapy with all-trans retinoic acid (ATRA).
  3. 3Perform a bone marrow aspiration and biopsy for morphologic and cytogenetic evaluation.
  4. 4Confirm the diagnosis via fluorescence in situ hybridization (FISH) for the t(15;17) translocation.

Answer

The correct sequence is: (1) Review the peripheral blood smear, (2) Initiate empiric all-trans retinoic acid (ATRA), (3) Perform bone marrow aspiration, and (4) Confirm the diagnosis with molecular testing (FISH).
The management of acute promyelocytic leukemia (APL) is a medical emergency. The patient's presentation of pancytopenia and severe coagulopathy (DIC) is highly suspicious for APL. The first step is to review a peripheral blood smear for hypergranular promyelocytes and Auer rods. Because APL is associated with life-threatening hemorrhage, all-trans retinoic acid (ATRA) must be initiated immediately based on this morphological suspicion alone. Bone marrow aspiration/biopsy and molecular testing (FISH for t(15;17)) are subsequently performed to confirm the diagnosis, but therapy should never be delayed while waiting for these definitive results.

Step-by-Step Solution

1
Identify clinical and laboratory signs of APL and DIC.
Suspicion for APL is raised based on pancytopenia and severe coagulopathy.
Recognizing the triad of pancytopenia, coagulopathy, and bleeding is critical for identifying this oncologic emergency.
2
Review the peripheral blood smear.
Detection of abnormal promyelocytes with Auer rods.
Provides immediate morphological evidence to justify emergent, life-saving targeted therapy.
3
Administer empiric ATRA.
Promotes differentiation of leukemic cells and rapidly improves coagulopathy.
Prevents fatal hemorrhagic complications of DIC. Must not be delayed for definitive molecular or bone marrow testing.
4
Perform bone marrow aspiration and molecular testing.
Definitive diagnosis of t(15;17) PML-RARA fusion.
Confirms the diagnosis and dictates the full induction chemotherapy regimen once the patient is hemodynamically stable.

Key Concept

In acute promyelocytic leukemia (APL), empiric treatment with all-trans retinoic acid (ATRA) must be initiated immediately upon morphological suspicion (e.g., peripheral smear), prior to definitive bone marrow and genetic confirmation, to prevent fatal hemorrhagic complications.
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Topics

Hematology and Oncology

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