Nutrition: rickets: practice question

A PSM 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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PSM · Nutrition: rickets

Sample item

A 10-month-old exclusively breastfed infant who is rarely taken outdoors has craniotabes, widened wrists and a rachitic rosary. Which biochemical pattern is expected?

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

The answer and the reasoning

D. Low or normal calcium, low phosphate, high alkaline phosphatase and high PTH

Vitamin D deficiency rickets reduces calcium absorption, causing secondary hyperparathyroidism. PTH raises urinary phosphate loss, so phosphate is low, while osteoblast activity raises alkaline phosphatase markedly. Serum calcium is low or low-normal because PTH keeps it up at the expense of bone.

Option by option

  • A. High calcium, high phosphate, normal alkaline phosphatase and low PTH

    High calcium with low PTH suggests vitamin D excess, not deficiency.

  • B. Low calcium, high phosphate, normal alkaline phosphatase and low PTH

    Low calcium with high phosphate and low PTH is the pattern of hypoparathyroidism.

  • C. High calcium, low phosphate, low alkaline phosphatase and low PTH

    High calcium with low alkaline phosphatase does not occur in rickets, where bone formation markers are raised.

  • D. Low or normal calcium, low phosphate, high alkaline phosphatase and high PTH (correct)

    Correct. Secondary hyperparathyroidism produces low phosphate and high alkaline phosphatase.

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.

More PSM questions

Questions about this PSM question

What is the answer to this PSM question?

The best answer is D, Low or normal calcium, low phosphate, high alkaline phosphatase and high PTH. Vitamin D deficiency rickets reduces calcium absorption, causing secondary hyperparathyroidism.

Why is "High calcium, high phosphate, normal alkaline phosphatase and low PTH" not the answer?

High calcium with low PTH suggests vitamin D excess, not deficiency.

Why is "Low calcium, high phosphate, normal alkaline phosphatase and low PTH" not the answer?

Low calcium with high phosphate and low PTH is the pattern of hypoparathyroidism.

Why is "High calcium, low phosphate, low alkaline phosphatase and low PTH" not the answer?

High calcium with low alkaline phosphatase does not occur in rickets, where bone formation markers are raised.

What concept does this question test?

It tests Nutrition: rickets in PSM. PTH raises urinary phosphate loss, so phosphate is low, while osteoblast activity raises alkaline phosphatase markedly. Serum calcium is low or low-normal because PTH keeps it up at the expense of bone.

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 Nutrition: rickets?

Practise biostatistics with small calculations until sensitivity, predictive values and risk measures are automatic. Then use the flashcards and the other PSM 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.