Haemodynamics: fat embolism syndrome: practice question

A Pathology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Pathology · Haemodynamics: fat embolism syndrome

Sample item

A 25-year-old man sustains a closed femoral shaft fracture in a road accident. Forty-eight hours later he becomes breathless and confused, and has petechiae over the chest, axillae and conjunctivae. Chest radiograph shows bilateral diffuse infiltrates and platelet count is mildly low. What is the most likely diagnosis?

AAnaphylaxis to an analgesicBAir embolism through a torn veinCFat embolism syndromeDPulmonary thromboembolism from deep vein thrombosis

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. Fat embolism syndrome

Fat embolism syndrome classically appears 1 to 3 days after long bone fracture with the triad of hypoxaemia with respiratory distress, neurological change and a petechial rash. Marrow fat enters torn venules, lodges in lung and brain capillaries, and is hydrolysed to free fatty acids that cause toxic endothelial injury. Treatment is supportive with oxygen and ventilatory support.

Option by option

A. Anaphylaxis to an analgesic
Anaphylaxis has urticaria, wheeze and hypotension within minutes of a drug, not petechiae after two days.
B. Air embolism through a torn vein
Air embolism is abrupt at the moment of venous entry and is not delayed by two days.
C. Fat embolism syndrome (correct)
Correct. Delayed onset after fracture with respiratory, neurological and petechial features defines the syndrome.
D. Pulmonary thromboembolism from deep vein thrombosis
Thromboembolism seldom causes petechiae or confusion, and imaging usually shows perfusion defects rather than diffuse bilateral infiltrates.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Pathology question

What is the answer to this Pathology question?

The best answer is C, Fat embolism syndrome. Fat embolism syndrome classically appears 1 to 3 days after long bone fracture with the triad of hypoxaemia with respiratory distress, neurological change and a petechial rash.

Why is "Anaphylaxis to an analgesic" not the answer?

Anaphylaxis has urticaria, wheeze and hypotension within minutes of a drug, not petechiae after two days.

Why is "Air embolism through a torn vein" not the answer?

Air embolism is abrupt at the moment of venous entry and is not delayed by two days.

Why is "Pulmonary thromboembolism from deep vein thrombosis" not the answer?

Thromboembolism seldom causes petechiae or confusion, and imaging usually shows perfusion defects rather than diffuse bilateral infiltrates.

What concept does this question test?

It tests Haemodynamics: fat embolism syndrome in Pathology. Marrow fat enters torn venules, lodges in lung and brain capillaries, and is hydrolysed to free fatty acids that cause toxic endothelial injury. Treatment is supportive with oxygen and ventilatory support.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Haemodynamics: fat embolism syndrome?

Learn each disease as a bundle: cause, key histology, markers, and the clinical hallmark. Then use the flashcards and the other Pathology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.