Toxicology: scombroid poisoning: 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 · Toxicology: scombroid poisoning

Sample item

Thirty minutes after eating tuna that was left unrefrigerated, a man develops flushing, headache, itching and palpitations. What is the mechanism?

AIgE-mediated allergy to fish proteinBCiguatoxin opening sodium channelsCHistamine produced by bacterial breakdown of fish fleshDTetrodotoxin blocking sodium channels

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

The answer and the reasoning

C. Histamine produced by bacterial breakdown of fish flesh

Spoiled scombroid fish such as tuna and mackerel contain high histamine from bacterial decarboxylation of histidine, producing an allergic-like illness in many diners. Antihistamines treat it. Tetrodotoxin causes paralysis and ciguatoxin causes gastrointestinal and neurological symptoms.

Option by option

A. IgE-mediated allergy to fish protein
A true IgE allergy would affect only a sensitised person and not several diners.
B. Ciguatoxin opening sodium channels
Ciguatoxin gives diarrhoea, paraesthesia and reversal of hot and cold sensation.
C. Histamine produced by bacterial breakdown of fish flesh (correct)
Correct. Bacterial histamine in spoiled fish explains the rapid flushing illness.
D. Tetrodotoxin blocking sodium channels
Tetrodotoxin from pufferfish causes numbness and ascending paralysis.

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 C, Histamine produced by bacterial breakdown of fish flesh. Spoiled scombroid fish such as tuna and mackerel contain high histamine from bacterial decarboxylation of histidine, producing an allergic-like illness in many diners.

Why is "IgE-mediated allergy to fish protein" not the answer?

A true IgE allergy would affect only a sensitised person and not several diners.

Why is "Ciguatoxin opening sodium channels" not the answer?

Ciguatoxin gives diarrhoea, paraesthesia and reversal of hot and cold sensation.

Why is "Tetrodotoxin blocking sodium channels" not the answer?

Tetrodotoxin from pufferfish causes numbness and ascending paralysis.

What concept does this question test?

It tests Toxicology: scombroid poisoning in Forensic Medicine. Antihistamines treat it. Tetrodotoxin causes paralysis and ciguatoxin causes gastrointestinal and neurological symptoms.

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 Toxicology: scombroid poisoning?

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.