Tissue repair: copper and collagen cross-linking: 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 · Tissue repair: copper and collagen cross-linking

Sample item

A 4-month-old boy has sparse, kinky, depigmented hair, hypotonia, seizures and tortuous arteries on imaging. Serum copper and ceruloplasmin are low. Which step of connective tissue synthesis is defective, accounting for the vascular and skeletal features?

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

The answer and the reasoning

A. Lysyl oxidase-mediated cross-linking of collagen and elastin

Menkes disease is an X-linked defect of the copper transporter ATP7A, which reduces the activity of copper-dependent enzymes including lysyl oxidase. Without cross-links, collagen and elastin lack strength, giving tortuous vessels and bone changes. Neurological damage comes from other copper enzymes such as cytochrome oxidase.

Option by option

  • A. Lysyl oxidase-mediated cross-linking of collagen and elastin (correct)

    Lysyl oxidase needs copper, so copper deficiency weakens collagen and elastin cross-links.

  • B. Cleavage of procollagen propeptides by N-peptidase

    Failure of N-peptidase cleavage causes dermatosparaxis-type Ehlers-Danlos syndrome with fragile skin, not low copper.

  • C. Hydroxylation of proline and lysine residues

    Proline and lysine hydroxylation needs vitamin C and iron, and it fails in scurvy rather than in copper deficiency.

  • D. Assembly of the glycine-rich collagen triple helix

    Glycine substitutions that disrupt the triple helix cause osteogenesis imperfecta, with normal copper.

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.

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Questions about this Pathology question

What is the answer to this Pathology question?

The best answer is A, Lysyl oxidase-mediated cross-linking of collagen and elastin. Menkes disease is an X-linked defect of the copper transporter ATP7A, which reduces the activity of copper-dependent enzymes including lysyl oxidase.

Why is "Cleavage of procollagen propeptides by N-peptidase" not the answer?

Failure of N-peptidase cleavage causes dermatosparaxis-type Ehlers-Danlos syndrome with fragile skin, not low copper.

Why is "Hydroxylation of proline and lysine residues" not the answer?

Proline and lysine hydroxylation needs vitamin C and iron, and it fails in scurvy rather than in copper deficiency.

Why is "Assembly of the glycine-rich collagen triple helix" not the answer?

Glycine substitutions that disrupt the triple helix cause osteogenesis imperfecta, with normal copper.

What concept does this question test?

It tests Tissue repair: copper and collagen cross-linking in Pathology. Without cross-links, collagen and elastin lack strength, giving tortuous vessels and bone changes. Neurological damage comes from other copper enzymes such as cytochrome oxidase.

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 Tissue repair: copper and collagen cross-linking?

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.