A 60-year-old man presents with gum bleeding and petechiae. CBC shows WBC 28,000/uL, hemoglobin 8 g/dL, platelets 18,000/uL. Prothrombin time and aPTT are prolonged, fibrinogen is 80 mg/dL, and D-dimer is markedly elevated. The peripheral smear shows abnormal promyelocytes with numerous Auer rods bundled together (faggot cells). Which cytogenetic abnormality is characteristic of this leukemia?
- A t(15;17)(q24;q21) ✓
- B inv(16)(p13q22)
- C t(8;21)(q22;q22)
- D t(9;22)(q34;q11)
Correct answer: A. t(15;17)(q24;q21)
Explanation
The coagulopathy with low fibrinogen plus faggot cells identifies acute promyelocytic leukemia (FAB M3), defined by t(15;17) fusing PML with RARA. The PML-RARA protein blocks myeloid differentiation, and it responds to all-trans retinoic acid, which overcomes the differentiation block. inv(16) defines AML M4Eo with eosinophilia, while t(8;21) defines AML M2; neither causes early DIC as their hallmark presentation.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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