Collagen: basement membrane defects: practice question

A Biochemistry 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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Biochemistry · Collagen: basement membrane defects

Sample item

A 12-year-old boy has haematuria, high-frequency sensorineural hearing loss and anterior lenticonus. His maternal uncle died of renal failure. Which protein is abnormal?

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

The answer and the reasoning

C. Type IV collagen

Alport syndrome is most often X-linked, caused by COL4A5 mutations that disrupt the alpha-5 chain of type IV collagen in glomerular, cochlear and lens basement membranes. Electron microscopy shows a lamellated glomerular basement membrane. Progression to end-stage kidney disease is faster in males.

Option by option

  • A. Type I collagen

    Type I collagen mutations cause osteogenesis imperfecta with blue sclerae and fractures.

  • B. Type III collagen

    Type III collagen defects cause vascular Ehlers-Danlos syndrome.

  • C. Type IV collagen (correct)

    Correct. Type IV collagen forms the network of basement membranes affected in this triad.

  • D. Type II collagen

    Type II collagen is in cartilage and vitreous, and its defects cause chondrodysplasias.

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 Biochemistry question

What is the answer to this Biochemistry question?

The best answer is C, Type IV collagen. Alport syndrome is most often X-linked, caused by COL4A5 mutations that disrupt the alpha-5 chain of type IV collagen in glomerular, cochlear and lens basement membranes.

Why is "Type I collagen" not the answer?

Type I collagen mutations cause osteogenesis imperfecta with blue sclerae and fractures.

Why is "Type III collagen" not the answer?

Type III collagen defects cause vascular Ehlers-Danlos syndrome.

Why is "Type II collagen" not the answer?

Type II collagen is in cartilage and vitreous, and its defects cause chondrodysplasias.

What concept does this question test?

It tests Collagen: basement membrane defects in Biochemistry. Electron microscopy shows a lamellated glomerular basement membrane. Progression to end-stage kidney disease is faster in males.

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 Collagen: basement membrane defects?

Build one table of enzyme deficiency, disease, inheritance and key finding, then revise it by spaced recall. Then use the flashcards and the other Biochemistry 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.