A 52-year-old man with a history of advanced pancreatic cancer presents to the emergency department with sudden-onset dyspnea, petechiae, and bleeding from multiple sites (gums, rectum, catheter site). His wife reports he was well until this morning. Laboratory results: hemoglobin 7.8 g/dL, platelet count 32,000/μL, PT 28 sec (normal 12–14), aPTT 52 sec (normal 24–36), fibrinogen 85 mg/dL (normal 200–400), D-dimer >10 μg/mL (normal <0.5). Blood smear shows schistocytes. What is the most likely diagnosis?

Explanation

## Clinical Presentation Analysis This patient presents with: - **Acute onset** of bleeding from multiple sites (gums, rectum, catheter) - **Thrombocytopenia** (32,000/μL) - **Coagulation abnormalities**: prolonged PT, prolonged aPTT - **Hypofibrinogenemia** (85 mg/dL) - **Elevated D-dimer** (>10 μg/mL) - **Schistocytes** on blood smear - **Underlying malignancy** (pancreatic cancer) ## DIC Diagnostic Criteria (ISTH Scoring System) **Key Point:** DIC is diagnosed when ≥5 points are present: | Parameter | Score | |-----------|-------| | Platelet count ≥100,000 | 0 | | Platelet count 50,000–99,999 | 1 | | **Platelet count <50,000** | **2** | | D-dimer/FDP elevation (moderate) | 2 | | **D-dimer/FDP elevation (strong)** | **3** | | PT prolongation <3 sec | 0 | | **PT prolongation ≥3 sec** | **1** | | **Fibrinogen <100 mg/dL** | **1** | **This patient scores ≥5 points (2 + 3 + 1 + 1 = 7), confirming DIC.** ## Pathophysiology of DIC ```mermaid flowchart TD A[Pancreatic cancer cells]:::outcome --> B[Release tissue factor & cancer procoagulants]:::action B --> C[Widespread thrombin generation]:::action C --> D[Platelet consumption & aggregation]:::outcome C --> E[Fibrinogen consumption]:::outcome C --> F[Activation of fibrinolysis]:::action D --> G[Thrombocytopenia]:::outcome E --> H[Hypofibrinogenemia]:::outcome F --> I[Elevated D-dimer & FDP]:::outcome D --> J[Microthrombi formation]:::outcome J --> K[Schistocytes on smear]:::outcome G --> L[Bleeding manifestations]:::urgent ``` ## Why This Is DIC (Not TTP or APL) **High-Yield:** DIC is a consumptive coagulopathy with: 1. **Prolonged PT/aPTT** (consumption of factors II, V, VII, X) 2. **Low fibrinogen** (consumption in fibrin formation) 3. **Elevated D-dimer** (secondary fibrinolysis) 4. **Thrombocytopenia** (platelet consumption) 5. **Schistocytes** (mechanical fragmentation in microthrombi) **Clinical Pearl:** The combination of **prolonged coagulation times + low fibrinogen + elevated D-dimer** is pathognomonic for DIC and distinguishes it from TTP (which has normal coagulation studies) and APL (which may have coagulopathy but typically presents with leukostasis or hemorrhage from leukemic burden, not acute DIC). ## Triggers of DIC **Mnemonic: STOP Making DIC** — **S**epsis, **T**rauma, **O**bstetric (placental abruption, amniotic fluid embolism), **M**alignancy (especially pancreatic, lung, prostate, acute leukemia) This patient's pancreatic cancer is a classic trigger. [cite:Harrison 21e Ch 179]