DIC & Consumptive Coagulopathy
A boards-focused walkthrough of DIC as a consumptive coagulopathy — from tissue-factor pathophysiology through its schistocyte / low-fibrinogen / high-D-dimer lab signature to cause-directed, next-best-step management — anchored by classic obstetric and APL vignettes and a comparison table that separates DIC from TTP-HUS, ITP, liver failure, and vitamin K deficiency.
Pathophysiology: One Process, Two Faces
DIC is never a primary disease — it is a systemic response to an underlying trigger. Massive exposure of tissue factor (from damaged endothelium, activated monocytes, tumor cells, or obstetric tissue) ignites uncontrolled thrombin generation and cascade activation. Two consequences run in parallel:
- Microthrombi deposit in small vessels → end-organ ischemia (AKI, delirium, digital gangrene) and microangiopathic hemolytic anemia (MAHA) as RBCs are sheared across fibrin strands into schistocytes.
- The runaway clotting consumes platelets and clotting factors faster than they can be replaced, while secondary fibrinolysis (plasmin) degrades fibrin.
So the same patient paradoxically bleeds and clots at once. Acute DIC (sepsis, trauma, obstetric catastrophe) presents with hemorrhage and oozing from lines; chronic/compensated DIC (mucinous adenocarcinoma, large aortic aneurysm, giant hemangioma) may present instead with thrombosis (Trousseau migratory thrombophlebitis).
- Thrombocytopenia — a falling platelet count is often the earliest clue
- PT and aPTT prolonged — coagulation factors are consumed
- Fibrinogen LOW — consumed; but it is an acute-phase reactant, so it may start high — a falling trend is what matters
- D-dimer / FDPs HIGH — the most sensitive finding; reflects plasmin-mediated fibrinolysis of cross-linked fibrin
- Schistocytes / helmet cells on smear (MAHA) — present but often fewer than in TTP/HUS
- ↑ LDH, ↓ haptoglobin, indirect hyperbilirubinemia — intravascular hemolysis
No single test is diagnostic. DIC is a pattern in context, and trends beat one-time values.
DIC is always secondary — pin the trigger and you've all but made the diagnosis. The four highest-yield settings spell MOST:
- M — Malignancy: acute promyelocytic leukemia (APL, AML-M3) and mucin-secreting adenocarcinomas (the latter → chronic DIC / Trousseau migratory thrombophlebitis)
- O — Obstetric: placental abruption, amniotic fluid embolism, retained dead fetus, severe pre-eclampsia / HELLP
- S — Sepsis: gram-negative endotoxin is the prototypical driver (also meningococcemia → purpura fulminans)
- T — Trauma: major trauma, crush injury, severe burns, extensive tissue necrosis
Also genuinely recognized: acute pancreatitis, an acute hemolytic (ABO-incompatible) transfusion reaction, and snake envenomation (venom-induced consumption coagulopathy).
If a vignette pairs one of these settings with new bleeding + a falling platelet count, think DIC first.
Consumptive & MAHA Differential
| Feature | DIC | TTP–HUS | ITP | Liver failure | Vit K deficiency |
|---|---|---|---|---|---|
| Platelets | ↓ | ↓ | ↓ | ↓/nl | nl |
| PT | ↑ | nl | nl | ↑ | ↑ (first) |
| aPTT | ↑ | nl | nl | ↑/nl | ↑ (later) |
| Fibrinogen | ↓ | nl | nl | ↓ | nl |
| D-dimer | ↑↑ | nl/↑ | nl | nl/↑ | nl |
| Schistocytes | yes | yes | no | no | no |
| Key marker | ↑FDPs | ↓ADAMTS13 (TTP) / Shiga toxin (HUS) | anti-GPIIb/IIIa Ab | factor V ↓, VIII nl/↑ | II,VII,IX,X ↓, V normal |
Vignette: A 30-year-old woman at 39 weeks becomes abruptly hypotensive and dyspneic during labor, then oozes blood from her IV sites, gums, and surgical incision. Labs: platelets 45k, PT and aPTT prolonged, fibrinogen 80 mg/dL, D-dimer markedly elevated, schistocytes on smear.
Diagnosis: Acute DIC from an obstetric trigger (amniotic fluid embolism / abruption).
Next best step:
- Treat the underlying cause — deliver/evacuate the uterus and support hemodynamics. This is the only definitive therapy.
- Replace what's consumed in a bleeding patient: cryoprecipitate (fibrinogen <100–150 mg/dL), FFP (prolonged PT/aPTT), platelets (<50k with bleeding).
- Do NOT give heparin in florid, actively hemorrhaging acute DIC.
Vignette: A 26-year-old presents with fatigue, easy bruising, and gingival bleeding. CBC shows pancytopenia with circulating blasts; marrow reveals promyelocytes packed with Auer rods — bundles = "faggot cells." PT/aPTT prolonged, fibrinogen low, D-dimer high.
Diagnosis: Acute promyelocytic leukemia (APL, AML-M3), t(15;17) → PML-RARA fusion, complicated by DIC (procoagulant granules; worsens with blast cytolysis).
Next best step: Start all-trans retinoic acid (ATRA) immediately on morphologic/clinical suspicion — do not wait for cytogenetic confirmation — because it differentiates the promyelocytes and rapidly abates the DIC. Add arsenic trioxide; support with cryoprecipitate and platelets. Anticipate differentiation syndrome (fever, dyspnea, pulmonary infiltrates, fluid overload).
Diagnose when a sick patient (sepsis, OB, trauma, APL) develops thrombocytopenia + prolonged PT/aPTT + low fibrinogen + high D-dimer + schistocytes. D-dimer/FDPs = most sensitive; fibrinogen and platelet trends track severity (ISTH scoring where available).
Manage in order:
- Treat the underlying cause — the only definitive therapy.
- Bleeding patient: cryoprecipitate (fibrinogen), FFP (factors), platelets; add vitamin K if concurrent deficiency.
- Thrombosis-predominant / chronic DIC (Trousseau, purpura fulminans): heparin/LMWH; give protein C concentrate in meningococcemia-associated purpura fulminans.
- Transfuse for active bleeding or a planned procedure — not merely to "correct the number."
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