A 42-year-old woman is evaluated in the intensive care unit for new-onset oozing of blood from her intravenous catheter sites and a widespread petechial rash. She was admitted two days ago for severe sepsis secondary to acute pyelonephritis. Her temperature is 38.8°C (101.8°F), blood pressure is 90/55 mmHg, and pulse is 118/min.
Laboratory studies show:
| Test | Result | Reference Range |
|---|---|---|
| Hemoglobin | 8.4 g/dL | 12.0-15.5 g/dL |
| Platelet count | 35,000/mm³ | 150,000-400,000/mm³ |
| Leukocyte count | 18,500/mm³ | 4,500-11,000/mm³ |
| Prothrombin time (PT) | 24 seconds | 11-15 seconds |
| Partial thromboplastin time (PTT) | 58 seconds | 25-40 seconds |
| Fibrinogen | 85 mg/dL | 200-400 mg/dL |
| D-dimer | 8,400 ng/mL | < 500 ng/mL |
Peripheral blood smear reveals numerous schistocytes.
Based on the laboratory findings, which of the following is the most likely diagnosis?
- Disseminated intravascular coagulationAnswer
- BThrombotic thrombocytopenic purpura
- CImmune thrombocytopenia
- DVitamin K deficiency
- EHeparin-induced thrombocytopenia
Answer
Disseminated intravascular coagulation
The correct diagnosis is disseminated intravascular coagulation (DIC). DIC is characterized by widespread, systemic activation of the coagulation cascade, leading to the formation of microthrombi throughout the microvasculature. This massive coagulation effort consumes platelets and clotting factors, resulting in thrombocytopenia, prolonged prothrombin time (PT), prolonged partial thromboplastin time (PTT), and low fibrinogen. Simultaneously, the fibrinolytic system is activated to break down these clots, leading to highly elevated levels of fibrin degradation products, such as D-dimer. As red blood cells are forced through small vessels partially occluded by fibrin strands, they are sheared, producing schistocytes (fragmented red blood cells) on the peripheral smear. Severe sepsis is one of the most common triggers for DIC.
Step-by-Step Solution
Key Concept
The diagnosis of disseminated intravascular coagulation requires identifying both a consumptive coagulopathy (prolonged PT/PTT, low fibrinogen, elevated D-dimer) and a microangiopathic hemolytic anemia (thrombocytopenia, schistocytes).