A 26-year-old man presents with gum bleeding and petechiae. CBC shows WBC 2,100/uL, hemoglobin 8 g/dL, platelets 18,000/uL. Peripheral smear shows promyelocytes with bilobed nuclei and numerous Auer rods. PT and aPTT are prolonged with fibrinogen of 80 mg/dL and D-dimer markedly elevated. What is the most appropriate initial therapy?
- A All-trans retinoic acid ✓
- B Hydroxyurea
- C Imatinib
- D Rituximab
Correct answer: A. All-trans retinoic acid
Explanation
The pancytopenia, faggot-cell promyelocytes, and florid DIC define acute promyelocytic leukemia (AML-M3), driven by the PML-RARA fusion of t(15;17). All-trans retinoic acid binds the fusion receptor, releasing the transcriptional block on granulocytic differentiation, and is given emergently alongside blood product support before chemotherapy. Imatinib targets BCR-ABL in CML, hydroxyurea is cytoreductive in myeloproliferative neoplasms, and rituximab is a B-cell agent, so none addresses the RARA block.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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