A 58-year-old man with a history of metastatic pancreatic cancer presents with acute onset of severe bleeding from a gastric ulcer. On admission: BP 88/54 mmHg, HR 112/min, RR 24/min. Laboratory findings: Hemoglobin 7.8 g/dL, Platelet count 45,000/μL, PT 18 seconds (normal 12–14), aPTT 48 seconds (normal 24–36), Fibrinogen 1.2 g/L (normal 2–4), D-dimer markedly elevated, Fibrin degradation products elevated. Blood film shows schistocytes. Which coagulation abnormality best explains this clinical presentation?

Explanation

## Diagnosis: Disseminated Intravascular Coagulation (DIC) ### Clinical Context and Triggers **Key Point:** Metastatic cancer (especially pancreatic adenocarcinoma) is a major trigger for DIC. Malignant cells release tissue factor (TF) and cancer procoagulants, initiating widespread thrombin generation and platelet consumption. ### DIC Pathophysiology ```mermaid flowchart TD A[Cancer cells release Tissue Factor & procoagulants]:::action --> B[Widespread thrombin generation]:::action B --> C[Platelet consumption & aggregation]:::action B --> D[Fibrinogen consumption]:::action B --> E[Activation of fibrinolysis]:::action C --> F[Thrombocytopenia]:::outcome D --> G[Hypofibrinogenemia]:::outcome E --> H[Elevated D-dimer & FDP]:::outcome F --> I[Bleeding + Microthrombi]:::urgent G --> I H --> I ``` ### Laboratory Findings in DIC | Parameter | Finding | Mechanism | |-----------|---------|----------| | PT | Prolonged (18 sec) | Consumption of factors II, V, VII, X | | aPTT | Prolonged (48 sec) | Consumption of factors VIII, IX, XI, XII | | Fibrinogen | Low (1.2 g/L) | Consumption by thrombin + fibrinolysis | | Platelets | Reduced (45,000/μL) | Consumption in microthrombi | | D-dimer | Markedly elevated | Fibrin breakdown by plasmin | | FDP | Elevated | Plasmin-mediated fibrinolysis | | Blood film | Schistocytes | Mechanical hemolysis from fibrin strands | **High-Yield:** The **pentad of DIC** = ↓Platelets + ↓Fibrinogen + ↑PT/aPTT + ↑D-dimer/FDP + Schistocytes. This patient has all five. ### Bleeding Manifestations in DIC **Clinical Pearl:** DIC causes a **paradoxical bleeding diathesis** — despite widespread thrombosis, patients bleed because: 1. Platelet consumption depletes hemostatic reserve 2. Fibrinogen consumption impairs clot formation 3. Plasmin-mediated fibrinolysis dissolves clots 4. Endothelial damage from microthrombi increases vascular permeability This patient's gastric ulcer bleeding is exacerbated by DIC-induced coagulopathy. ### DIC Scoring (ISTH Criteria) Points are assigned for: - Platelet count (0–3 points) - D-dimer/FDP elevation (0–3 points) - PT prolongation (0–1 point) - Fibrinogen level (0–1 point) **Score ≥5 = Overt DIC** (this patient scores ≥5) ### Why This Is NOT the Other Options **Mnemonic:** **DIC vs. Other Coagulopathies** — **D**isseminated (widespread), **I**ntrinsic + **E**xtrinsic (both pathways), **C**onsumption (platelets, fibrinogen, factors) [cite:Harrison 21e Ch 181, Robbins 10e Ch 13]