In a critically ill septic patient with hemorrhage, vascular occlusion, ischemia, tissue necrosis, and schistocytes on peripheral blood smear, what is the most likely diagnosis?

Disseminated Intravascular Coagulation (DIC)

The correct answer is D. Disseminated Intravascular Coagulation (DIC). This critically ill septic patient presenting with hemorrhage, vascular occlusion, ischemia, tissue necrosis, and schistocytes on peripheral blood smear has the pathognomonic features of overt DIC, which represents the decompensated stage of sepsis-induced coagulopathy. 1

Why DIC is the Correct Diagnosis

The presence of schistocytes (fragmented red blood cells) is the key diagnostic finding that distinguishes DIC from the other options. Schistocytes indicate microangiopathic hemolytic anemia resulting from widespread microvascular thrombosis with mechanical shearing of red blood cells as they pass through fibrin-laden microvasculature. 2, 3

Clinical Features That Confirm DIC

• Hemorrhage occurs due to consumption of platelets and coagulation factors from widespread activation of the clotting cascade. 4, 5

• Vascular occlusion, ischemia, and tissue necrosis result from microvascular thrombosis and fibrin deposition throughout the microvasculature, leading to impaired tissue perfusion and multiple organ dysfunction. 3, 6

• Sepsis as the underlying trigger is the most common cause of DIC, with the overwhelming inflammatory response driving aberrant tissue factor expression, impairment of anticoagulant pathways, and suppression of fibrinolysis. 2, 3

Why the Other Options Are Incorrect

Vitamin K Deficiency (Option A)

• Vitamin K deficiency causes prolonged PT and aPTT due to decreased synthesis of factors II, VII, IX, and X, but does not cause schistocytes, thrombocytopenia, or the combination of bleeding with thrombosis. 4

• Vitamin K deficiency presents with bleeding alone, not the microvascular thrombosis, ischemia, and tissue necrosis seen in this patient. 4

Liver Disease (Option B)

• Liver disease impairs synthesis of coagulation factors and can cause prolonged PT/aPTT and thrombocytopenia, but schistocytes are not a feature of liver disease. 2

• The International Society on Thrombosis and Haemostasis notes that antithrombin levels help distinguish DIC (decreased due to consumption) from chronic liver disease (decreased due to impaired synthesis). 2

• Liver disease does not cause the acute microvascular thrombosis with ischemia and tissue necrosis characteristic of DIC. 3

Lupus Inhibitor (Option C)

• Lupus anticoagulant is an antiphospholipid antibody that paradoxically causes thrombosis despite prolonging aPTT in vitro, but does not cause schistocytes, consumptive coagulopathy, or the acute hemorrhagic-thrombotic picture of DIC. 4

• Lupus anticoagulant-associated thrombosis is typically venous or arterial macrovascular thrombosis, not the widespread microvascular thrombosis of DIC. 6

Diagnostic Confirmation

The International Society on Thrombosis and Haemostasis recommends a two-step diagnostic approach for septic patients: 1, 7

• Step 1: Screen all septic patients with thrombocytopenia (platelet count <150 × 10⁹/L) using Sepsis-Induced Coagulopathy (SIC) criteria, which incorporate platelet count, PT-INR, and SOFA score (≥4 points indicates SIC). 7, 8

• Step 2: If SIC criteria are met, assess for overt DIC using ISTH overt-DIC criteria (≥5 points confirms overt DIC), which incorporate platelet count, PT prolongation, elevated fibrin markers (D-dimer/FDP), and fibrinogen levels. 2, 9

Expected Laboratory Findings in This Patient

• Thrombocytopenia from platelet consumption in microvascular thrombi. 7, 5

• Prolonged PT and aPTT reflecting consumption of coagulation factors. 2, 4

• Elevated D-dimer and fibrin degradation products (FDP) indicating ongoing fibrinolysis; the D-dimer and FDP combination has 95% diagnostic efficiency for DIC. 9

• Decreased fibrinogen in advanced cases due to consumption (though fibrinogen may be normal or elevated initially in sepsis due to acute phase response). 1, 2

• Decreased antithrombin due to consumption, which helps distinguish DIC from liver disease. 2, 5

Clinical Significance and Prognosis

• Sepsis is the most common cause of DIC, with mortality of 24.8% when DIC develops in septic patients. 7

• The reported mortality of SIC is ≥30%, and almost all patients with overt DIC were diagnosed with SIC at an earlier stage. 1

• Symmetrical peripheral gangrene (SPG) represents a devastating consequence of sepsis-associated DIC, with potential acral limb loss from microvascular thrombosis. 1, 8