## Most Common Malignancy-Associated DIC **Key Point:** Acute promyelocytic leukemia (APL, AML M3) is the most common hematologic malignancy causing DIC, occurring in 80–90% of untreated APL cases. ### Why APL Causes DIC **High-Yield:** APL leukemic cells contain abundant **azurophilic granules** packed with: - Tissue factor (TF) - Cancer procoagulant (a cysteine protease) - Phosphatidylserine on cell membranes These substances directly activate the coagulation cascade and trigger DIC, especially during: 1. Initial diagnosis (high leukemic burden) 2. Early chemotherapy (cell lysis releases granule contents) ### Malignancy-Associated DIC — Comparative Frequency | Malignancy | Frequency | Mechanism | |------------|-----------|----------| | **Acute promyelocytic leukemia (APL)** | **80–90%** | Tissue factor + cancer procoagulant in granules | | Adenocarcinoma (pancreas, gastric, lung) | 5–15% | Tissue factor expression on tumor cells | | Small cell lung cancer | ~10% | Tissue factor expression | | Acute monocytic leukemia (AML M5) | ~10% | Monocytic TF release | **Clinical Pearl:** APL-DIC is a medical emergency. Patients present with: - Bleeding (petechiae, ecchymoses, mucosal bleeding) - Thrombocytopenia (<50,000/μL) - Hypofibrinogenemia (<100 mg/dL) - Elevated D-dimer and FDP - Prolonged PT/aPTT **Mnemonic — APL-DIC Triggers:** **"CHEMO"** - **C**ell lysis during chemotherapy - **H**igh leukemic burden at diagnosis - **E**xocytosis of azurophilic granules - **M**assive TF and procoagulant release - **O**verwhelmingly activates coagulation **Warning:** Do not confuse APL-DIC with other leukemias — while acute monocytic leukemia (AML M5) can cause DIC, it is far less frequent than APL. Solid tumors (pancreatic, gastric, lung adenocarcinoma) cause DIC through tissue factor expression on tumor cells, but this is much less common than APL.
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.