A 22-year-old man develops breathlessness, confusion and a rash 36 hours after intramedullary nailing of a femoral shaft fracture sustained in a road traffic accident. On examination there are petechiae over the anterior chest wall and axillae. SpO2 is 88% on room air. The petechial rash of this condition characteristically:
- A Appears within the first 4 hours after injury
- B Is confined to the lower limbs below the site of fracture
- C Occurs over the chest, axillae, neck and conjunctivae 24 to 72 hours after injury ✓
- D Is present only in patients with pre-existing coagulopathy
Correct answer: C. Occurs over the chest, axillae, neck and conjunctivae 24 to 72 hours after injury
Explanation
Fat embolism syndrome typically presents 24 to 72 hours after long bone fracture with hypoxia, neurological changes and a petechial rash distributed over the non-dependent upper body: chest, axillae, neck, conjunctivae and oral mucosa. The classic triad is respiratory distress, cerebral involvement and petechiae. Early onset within hours suggests another cause, and the rash reflects embolisation of fat globules through pulmonary capillaries, not local limb pathology.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.