A 28-year-old man presents with gum bleeding, ecchymoses, and prolonged bleeding after a minor cut. CBC shows pancytopenia with 40% blasts. Bone marrow shows hypergranular promyelocytes with bundles of Auer rods. D-dimer and fibrin split products are markedly elevated, fibrinogen is low. Which translocation is diagnostic, and what is the specific differentiation therapy that targets the underlying fusion protein?
- A t(8;21); all-trans retinoic acid (ATRA)
- B t(15;17); all-trans retinoic acid (ATRA) combined with arsenic trioxide ✓
- C inv(16); gemtuzumab ozogamicin
- D t(9;22); imatinib
Correct answer: B. t(15;17); all-trans retinoic acid (ATRA) combined with arsenic trioxide
Explanation
Hypergranular promyelocytes with Auer rods and DIC are classic for acute promyelocytic leukemia (AML-M3). The hallmark is t(15;17) producing PML-RARA. ATRA induces differentiation of leukemic promyelocytes by degrading the PML-RARA fusion protein; combined with arsenic trioxide it is the standard non-chemotherapy regimen for low-to-intermediate risk APL. t(8;21) and inv(16) are favorable risk translocations but not treated primarily with ATRA.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
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