## Most Common Hematologic Cause of DIC **Key Point:** Acute promyelocytic leukemia (APL, AML-M3) is the most common hematologic malignancy associated with DIC, occurring in 80–90% of untreated APL cases. ### Mechanism of DIC in APL APL cells contain abundant azurophilic granules packed with: - Tissue factor (TF) - Cancer procoagulant - Phosphatidylserine on cell surface When leukemic blasts undergo lysis (spontaneously or during chemotherapy induction), these procoagulant substances are released into circulation, triggering massive thrombin generation and consumption of platelets and fibrinogen. ### Clinical Presentation **High-Yield:** DIC in APL manifests as: - Severe bleeding (mucosal, cutaneous, intracranial) - Thrombocytopenia - Hypofibrinogenemia - Elevated D-dimer and PT/INR - Microangiopathic hemolytic anemia (MAHA) may occur ### Laboratory Findings in DIC | Parameter | Finding | |-----------|----------| | Platelet count | ↓ (consumption) | | Fibrinogen | ↓ (consumption) | | PT/INR | ↑ (factor consumption) | | aPTT | ↑ (factor consumption) | | D-dimer | ↑↑ (fibrinolysis) | | Fibrin degradation products (FDP) | ↑ | | Blood smear | Schistocytes (if MAHA present) | ### Why APL is the Worst Offender **Clinical Pearl:** APL has the highest risk of fatal hemorrhage among all leukemias due to DIC. The combination of: 1. Extreme procoagulant activity from leukemic blasts 2. Rapid cell turnover and lysis 3. Thrombocytopenia from marrow infiltration ...creates a "perfect storm" for catastrophic bleeding. **Mnemonic: APL-DIC = "All Procoagulants Lost"** — the disease literally spills clotting factors into the bloodstream. ### Management Implications - Early recognition and aggressive chemotherapy (ATRA + arsenic trioxide) is life-saving - Supportive transfusion of platelets, fresh frozen plasma (FFP), and cryoprecipitate - Avoid aggressive diuresis or hyperventilation (risk of intracranial hemorrhage) - DIC typically resolves within days of achieving complete remission [cite:Robbins 10e Ch 13]
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