Clinical meaning
Disseminated intravascular coagulation (DIC) involves systemic activation of coagulation triggered by tissue factor release (sepsis, trauma, malignancy, obstetric emergencies). Widespread microvascular thrombosis consumes platelets, fibrinogen, and clotting factors while simultaneously activating fibrinolysis, producing the paradox of simultaneous thrombosis AND bleeding. Heparin-induced thrombocytopenia (HIT) type II is an immune-mediated prothrombotic disorder: heparin binds platelet factor 4 (PF4), creating a neoantigen; IgG antibodies against heparin-PF4 complexes activate platelets via FcγRIIa receptors, causing intense platelet activation, aggregation, and thrombin generation. Despite thrombocytopenia, the predominant risk is THROMBOSIS (white clot syndrome), not bleeding.
Diagnosis & workup
Diagnostics & workup: - DIC panel: low platelets, low fibrinogen (<100), elevated D-dimer/FDP, prolonged PT and aPTT, schistocytes on blood smear (microangiopathic hemolytic anemia) - ISTH DIC scoring system: platelets, fibrinogen, D-dimer, PT prolongation; score ≥5 = overt DIC - HIT: 4Ts scoring (Thrombocytopenia severity, Timing of onset, Thrombosis, oTher causes); anti-PF4/heparin antibody (ELISA -- high sensitivity, moderate specificity); serotonin release assay (SRA -- gold standard, high specificity) - TTP pentad: thrombocytopenia, microangiopathic hemolytic anemia (schistocytes), neurological symptoms, renal impairment, fever (full pentad uncommon) - ADAMTS13 activity: <10% diagnostic for TTP; autoantibody (acquired) vs congenital deficiency - PLASMIC score: predicts ADAMTS13 deficiency to guide empiric plasma exchange before ADAMTS13 result available