Clinical report. Benefits from genetic test in descendants of familial adenomatous polyposis syndrome: report of a family in southern Thailand

Background: Familial adenomatous polyposis (FAP) is an inherited colorectal cancer predisposing syndrome that has an autosomal dominant mode of inheritance with complete penetrance. Although the disease-causing gene of FAP, the adenomatous polyposis coli (APC) gene, is well understood, genetic testing for FAP remains uncommon in Thailand, possibly because of its high cost.

Objective: Present a family in southern Thailand that had benefited from this test.

Subject and methods: The proband was a 31-year-old man who had rectal cancer with profuse adenomatous polyposis of his colon.

Results: APC mutation screening revealed a novel mutation at codon 1249 (TGC1249TAA) that could predict a premature stop codon. On screening of three siblings in the same generation who were alive and 11 members of the descendant generation, four cases were positive for the mutation. The positive members were confirmed to have a type of diffuse colonic polyposis by endoscopy, and a prophylactic colectomy was performed without complications for every affected individual.

Conclusion: A genetic test is cost-effective. It should be considered for FAP, especially when the number of at-risk family members is high.