Colorectal: familial adenomatous polyposis: practice question

A General Surgery 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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General Surgery · Colorectal: familial adenomatous polyposis

Sample item

A 17-year-old boy has rectal bleeding. Colonoscopy shows more than 200 adenomatous polyps throughout the colon. His father had a colectomy for colon cancer at the age of 36. Which germline defect and plan fit best?

AAPC gene mutation; prophylactic colectomy in early adulthoodBMLH1 gene mutation; colonoscopy every 1 to 2 yearsCSTK11 gene mutation; endoscopic polypectomy of hamartomasDSMAD4 gene mutation; annual faecal occult blood testing

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

The answer and the reasoning

A. APC gene mutation; prophylactic colectomy in early adulthood

Familial adenomatous polyposis is autosomal dominant, caused by a germline APC mutation on chromosome 5q21. Hundreds to thousands of adenomas appear in adolescence and the cancer risk approaches 100% by middle age, so prophylactic colectomy (proctocolectomy or colectomy with ileorectal anastomosis) is advised in early adulthood. Duodenal adenomas need lifelong surveillance.

Option by option

A. APC gene mutation; prophylactic colectomy in early adulthood (correct)
APC loss gives near-certain colorectal cancer, so prophylactic surgery is the standard of care.
B. MLH1 gene mutation; colonoscopy every 1 to 2 years
MLH1 mutation causes Lynch syndrome with few polyps, managed by surveillance rather than a polyposis picture.
C. STK11 gene mutation; endoscopic polypectomy of hamartomas
STK11 mutation causes Peutz-Jeghers syndrome with hamartomatous polyps and mucocutaneous pigmentation.
D. SMAD4 gene mutation; annual faecal occult blood testing
SMAD4 mutation causes juvenile polyposis with hamartomatous polyps, and faecal occult blood testing is inadequate in any polyposis.

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 General Surgery question

What is the answer to this General Surgery question?

The best answer is A, APC gene mutation; prophylactic colectomy in early adulthood. Familial adenomatous polyposis is autosomal dominant, caused by a germline APC mutation on chromosome 5q21.

Why is "MLH1 gene mutation; colonoscopy every 1 to 2 years" not the answer?

MLH1 mutation causes Lynch syndrome with few polyps, managed by surveillance rather than a polyposis picture.

Why is "STK11 gene mutation; endoscopic polypectomy of hamartomas" not the answer?

STK11 mutation causes Peutz-Jeghers syndrome with hamartomatous polyps and mucocutaneous pigmentation.

Why is "SMAD4 gene mutation; annual faecal occult blood testing" not the answer?

SMAD4 mutation causes juvenile polyposis with hamartomatous polyps, and faecal occult blood testing is inadequate in any polyposis.

What concept does this question test?

It tests Colorectal: familial adenomatous polyposis in General Surgery. Hundreds to thousands of adenomas appear in adolescence and the cancer risk approaches 100% by middle age, so prophylactic colectomy (proctocolectomy or colectomy with ileorectal anastomosis) is advised in early adulthood. Duodenal adenomas need lifelong surveillance.

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 Colorectal: familial adenomatous polyposis?

Learn classic signs and eponyms alongside what they diagnose. Then use the flashcards and the other General Surgery 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.