Fat embolism syndrome (FES) typically develops 24–72 hours after a major long bone fracture. The definitive diagnostic criteria (Gurd's criteria) requiring 2 major OR 1 major + 4 minor criteria include a pathognomonic finding that distinguishes FES from other causes of respiratory distress. This pathognomonic finding is:
- A Hypoxaemia (PaO2 <60 mmHg) on room air
- B Petechial rash in a non-dependent distribution (upper chest, axillae, conjunctivae) ✓
- C Confusion and altered mental status
- D Chest X-ray showing bilateral infiltrates
Explanation
The petechial rash appearing in the non-dependent distribution (upper chest, axillae, conjunctivae, retina) is the pathognomonic major criterion of fat embolism syndrome and is present in 50–60% of confirmed FES cases. It results from fat globules occluding dermal capillaries causing petechiae without thrombocytopenia as the mechanism. The other major Gurd criteria are hypoxaemia (PaO2 <60 mmHg) and neurological signs. Gurd's minor criteria include tachycardia, pyrexia, retinal changes, jaundice, fat in urine/sputum, and falling haematocrit. Bilateral infiltrates are also seen but are non-specific (also in ARDS/pneumonia). The triad of respiratory distress + neurological dysfunction + petechiae is classic FES.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
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