A 28-year-old woman presents to the emergency department with severe epistaxis and petechiae. Peripheral blood smear shows numerous blasts with Auer rods (marked **A** in the diagram). She is found to have a platelet count of 18,000/µL and PT/aPTT are markedly prolonged. A bone marrow aspirate confirms acute promyelocytic leukemia (APL) with t(15;17). Which of the following is the MOST appropriate immediate management to prevent life-threatening hemorrhage in this patient?

Explanation

## Why "Start all-trans retinoic acid (ATRA) immediately and transfuse fresh frozen plasma and cryoprecipitate; avoid tranexamic acid" is right The structure marked **A** — the Auer rod — is pathognomonic for acute myeloid leukemia and, when present in bundles ("faggot cells"), is characteristic of acute promyelocytic leukemia (APL, AML M3). APL is a clinical emergency because the leukemic promyelocytes contain abundant primary (azurophilic) granules that release tissue factor and annexin II, triggering disseminated intravascular coagulation (DIC) and severe bleeding — the leading cause of early death within 2 weeks of diagnosis. Immediate management requires: (1) ATRA (tretinoin) to induce differentiation and halt the coagulopathy; (2) aggressive supportive care with fresh frozen plasma and cryoprecipitate to replace fibrinogen and clotting factors; and (3) avoidance of tranexamic acid, which paradoxically worsens coagulopathy in APL. This combined approach, often initiated on clinical/morphologic suspicion before cytogenetic confirmation, is the standard of care and achieves > 90% cure rates when combined with arsenic trioxide (Robbins 10e Ch 13; Harrison 21e Ch 102). ## Why each distractor is wrong - **Initiate intensive chemotherapy (daunorubicin + cytarabine) and transfuse packed red blood cells**: Traditional cytotoxic chemotherapy is NOT first-line in APL and may worsen the coagulopathy by causing further lysis of leukemic cells and release of procoagulant material. ATRA is the cornerstone of induction therapy. Packed RBCs alone do not address the underlying coagulopathy or fibrinogen depletion. - **Administer tranexamic acid and platelet transfusion to target platelet count > 100,000/µL**: Tranexamic acid is explicitly CONTRAINDICATED in APL because it worsens the coagulopathy. While platelet transfusion is part of supportive care, the target is 30,000–50,000/µL, not > 100,000/µL. Tranexamic acid is a critical error in APL management. - **Start arsenic trioxide monotherapy and observe for spontaneous resolution of coagulopathy**: Arsenic trioxide is highly effective in APL but is used in combination with ATRA, not as monotherapy for acute presentation. Observation without ATRA and aggressive coagulopathy management would be dangerous and delay life-saving intervention in this medical emergency. **High-Yield:** Auer rods = AML; Auer rods in bundles (faggot cells) = APL (t(15;17)); APL + DIC = ATRA + supportive care (FFP, cryo, avoid tranexamic acid) = emergency management. [cite: Robbins 10e Ch 13; Harrison 21e Ch 102]