A 34-year-old woman presents to the emergency department with acute onset severe headache, confusion, and fever (38.5°C). On examination, she has petechial rash over the lower extremities and trunk. Laboratory investigations reveal: Hb 9.2 g/dL, WBC 18,500/μL, platelets 45,000/μL, PT 18 s (normal 12–14 s), aPTT 42 s (normal 26–36 s), fibrinogen 120 mg/dL (normal 200–400 mg/dL), D-dimer 5000 ng/mL. Blood culture is pending. What is the most likely diagnosis?

Question

A 34-year-old woman presents to the emergency department with acute onset severe headache, confusion, and fever (38.5°C). On examination, she has petechial rash over the lower extremities and trunk. Laboratory investigations reveal: Hb 9.2 g/dL, WBC 18,500/μL, platelets 45,000/μL, PT 18 s (normal 12–14 s), aPTT 42 s (normal 26–36 s), fibrinogen 120 mg/dL (normal 200–400 mg/dL), D-dimer >5000 ng/mL. Blood culture is pending. What is the most likely diagnosis?

Accepted Answer

A. Disseminated intravascular coagulation secondary to meningococcal sepsis. ## Clinical Presentation & Diagnosis

**Key Point:** The constellation of fever, petechial rash, meningeal signs (headache, confusion), thrombocytopenia, and coagulopathy (prolonged PT/aPTT, low fibrinogen, elevated D-dimer) is pathognomonic for disseminated intravascular coagulation (DIC) secondary to meningococcal sepsis.

## Pathophysiology of DIC in Meningococcal Sepsis

1. Bacterial endotoxin (LPS) triggers tissue factor (TF) expression on monocytes and endothelial cells
2. Massive thrombin generation → consumption of platelets and clotting factors
3. Secondary fibrinolysis → elevated D-dimer and low fibrinogen
4. Microthrombi in skin → petechial/purpuric rash (often non-blanching)
5. Meningeal involvement → CNS manifestations

## Laboratory Interpretation

| Parameter | Finding | Significance |
|-----------|---------|---------------|
| Platelets | 45,000/μL | Consumption coagulopathy |
| PT/aPTT | Prolonged | Factor consumption |
| Fibrinogen | 120 mg/dL | Consumption + secondary fibrinolysis |
| D-dimer | >5000 ng/mL | Massive thrombin generation & fibrinolysis |
| Hb | 9.2 g/dL | Hemolysis from microangiopathy |

**High-Yield:** DIC scoring (ISTH criteria) requires ≥5 points from: platelet count, D-dimer/FDP elevation, PT prolongation, fibrinogen level. This patient scores ≥5 → confirmed DIC.

## Clinical Pearl

**Meningococcal sepsis is the classic presentation of fulminant DIC in clinical practice.** The petechial rash that does NOT blanch on pressure is a red flag for meningococcemia with DIC — this is a medical emergency requiring immediate antibiotics (ceftriaxone 2 g IV 4-hourly) and supportive care (FFP, platelets, cryoprecipitate as per DIC protocol).

## Management Algorithm

```mermaid
flowchart TD
  A[Fever + Petechial rash + Meningeal signs]:::outcome --> B{DIC criteria met?}:::decision
  B -->|Yes| C[Start empiric antibiotics immediately]:::urgent
  C --> D[Blood cultures before antibiotics if possible]:::action
  D --> E[Supportive transfusion: FFP, platelets, cryo]:::action
  E --> F[Anticoagulation: consider heparin if ongoing thrombosis]:::action
  F --> G[Source control: meningitis protocol]:::action
```

[cite:Harrison 21e Ch 182]

Answer

B. Immune thrombocytopenic purpura with secondary infection

Answer

C. Thrombotic thrombocytopenic purpura with bacterial superinfection

Answer

D. Heparin-induced thrombocytopenia with septic shock

Explanation

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