Toxicology: naphthalene in G6PD deficiency: 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: naphthalene in G6PD deficiency

Sample item

A 3-year-old boy with G6PD deficiency swallowed a mothball and two days later has pallor, jaundice and dark urine. What is the underlying process?

AFragmentation of red cells in small vesselsBOxidative haemolysis of red cellsCAntibody-mediated destruction of red cellsDBone marrow suppression by the toxin

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

The answer and the reasoning

B. Oxidative haemolysis of red cells

Naphthalene is metabolised to oxidant products that damage red cells lacking G6PD, because they cannot regenerate reduced glutathione. Haemoglobin denatures into Heinz bodies, and the cells are haemolysed. Mothballs should be kept out of reach of children, and G6PD-deficient patients should avoid them.

Option by option

A. Fragmentation of red cells in small vessels
Microangiopathic haemolysis requires fibrin strands in small vessels, which are not involved here.
B. Oxidative haemolysis of red cells (correct)
Correct. Oxidant stress causes haemolysis in G6PD-deficient cells.
C. Antibody-mediated destruction of red cells
Autoimmune haemolysis involves antibodies, which are not part of this mechanism.
D. Bone marrow suppression by the toxin
Marrow aplasia would reduce red cell production and not cause dark urine two days after ingestion.

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 B, Oxidative haemolysis of red cells. Naphthalene is metabolised to oxidant products that damage red cells lacking G6PD, because they cannot regenerate reduced glutathione.

Why is "Fragmentation of red cells in small vessels" not the answer?

Microangiopathic haemolysis requires fibrin strands in small vessels, which are not involved here.

Why is "Antibody-mediated destruction of red cells" not the answer?

Autoimmune haemolysis involves antibodies, which are not part of this mechanism.

Why is "Bone marrow suppression by the toxin" not the answer?

Marrow aplasia would reduce red cell production and not cause dark urine two days after ingestion.

What concept does this question test?

It tests Toxicology: naphthalene in G6PD deficiency in Forensic Medicine. Haemoglobin denatures into Heinz bodies, and the cells are haemolysed. Mothballs should be kept out of reach of children, and G6PD-deficient patients should avoid them.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. 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: naphthalene in G6PD deficiency?

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.