A 29-year-old man with familial adenomatous polyposis (FAP) undergoes a restorative proctocolectomy. He develops a desmoid tumour in the small bowel mesentery 2 years later. Which FAP genotype is most associated with mesenteric desmoid disease?
- A APC mutation in codon 1309 (exon 15)
- B APC mutation before codon 200
- C APC mutation between codons 1310–1444 ✓
- D MUTYH biallelic mutation
Correct answer: C. APC mutation between codons 1310–1444
Explanation
Desmoid tumours in FAP are strongly associated with APC mutations in the region between codons 1310 and 1444 (especially around codon 1444), the desmoid region of APC. Mutations at codon 1309 cause an attenuated phenotype with early colorectal cancer. Mutations before codon 200 cause AFAP (attenuated FAP) with fewer polyps. MUTYH-associated polyposis causes a FAP-like phenotype but is recessive.
Reference: Bailey & Love's Short Practice of Surgery, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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