Injuries: fat embolism at autopsy: practice question

A Forensic Medicine 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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Forensic Medicine · Injuries: fat embolism at autopsy

Sample item

A 32-year-old man with a fractured femoral shaft collapses on the third day and dies with petechiae over the chest and conjunctivae. Fat embolism is suspected. Which laboratory technique best demonstrates fat in the lung at autopsy?

AOil Red O or Sudan staining of frozen sectionsBHaematoxylin and eosin staining of paraffin sectionsCPerls Prussian blue staining of paraffin sectionsDPeriodic acid-Schiff staining of paraffin sections

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

The answer and the reasoning

A. Oil Red O or Sudan staining of frozen sections

Routine paraffin processing uses alcohol and xylene that dissolve fat, so fat globules in pulmonary capillaries are lost. Fresh frozen sections stained with a fat stain such as Oil Red O or Sudan III or IV preserve and show the globules. The clinical picture of respiratory distress, cerebral signs and petechiae one to three days after a long bone fracture fits fat embolism syndrome.

Option by option

A. Oil Red O or Sudan staining of frozen sections (correct)
Correct. Fat stains on frozen sections preserve and reveal neutral fat.
B. Haematoxylin and eosin staining of paraffin sections
Paraffin processing dissolves the fat, leaving empty spaces that are hard to prove.
C. Perls Prussian blue staining of paraffin sections
Perls stain demonstrates iron in haemosiderin, not fat.
D. Periodic acid-Schiff staining of paraffin sections
PAS stain demonstrates glycogen and mucin, not neutral fat.

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 Forensic Medicine question

What is the answer to this Forensic Medicine question?

The best answer is A, Oil Red O or Sudan staining of frozen sections. Routine paraffin processing uses alcohol and xylene that dissolve fat, so fat globules in pulmonary capillaries are lost.

Why is "Haematoxylin and eosin staining of paraffin sections" not the answer?

Paraffin processing dissolves the fat, leaving empty spaces that are hard to prove.

Why is "Perls Prussian blue staining of paraffin sections" not the answer?

Perls stain demonstrates iron in haemosiderin, not fat.

Why is "Periodic acid-Schiff staining of paraffin sections" not the answer?

PAS stain demonstrates glycogen and mucin, not neutral fat.

What concept does this question test?

It tests Injuries: fat embolism at autopsy in Forensic Medicine. Fresh frozen sections stained with a fat stain such as Oil Red O or Sudan III or IV preserve and show the globules. The clinical picture of respiratory distress, cerebral signs and petechiae one to three days after a long bone fracture fits fat embolism syndrome.

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 Injuries: fat embolism at autopsy?

Learn postmortem changes with their timelines, and toxicology as poison, sign, test and antidote. Then use the flashcards and the other Forensic Medicine 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.