A 32-year-old woman presents with bleeding gums, petechiae, and fever. CBC: WBC 18,000/uL, Hb 8.0 g/dL, platelets 12,000/uL. PT and aPTT are prolonged, fibrinogen is 80 mg/dL, and D-dimer is markedly elevated. Peripheral smear shows numerous large promyelocytes with bundled azurophilic granules. Which cytogenetic abnormality is the diagnostic hallmark?
- A t(15;17)(q24;q21) producing PML-RARA ✓
- B t(8;21)(q22;q22) producing RUNX1-RUNX1T1
- C inv(16)(p13q22) producing CBFB-MYH11
- D t(9;22)(q34;q11) producing BCR-ABL1
Correct answer: A. t(15;17)(q24;q21) producing PML-RARA
Explanation
Acute promyelocytic leukaemia (FAB M3) is defined by t(15;17), which fuses PML on chromosome 15 to RARA on chromosome 17, producing a fusion protein that blocks myeloid differentiation at the promyelocyte stage. The coagulopathy with low fibrinogen reflects DIC from tissue-factor-rich granules. t(8;21) and inv(16) are other favourable-risk core binding factor lesions but present without this fulminant coagulopathy, and t(9;22) defines CML or Ph-positive ALL.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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