Progressive Duodenal Adenomatosis in a Familial Adenomatous Polyposis Pedigree with APC Mutation at Codon 1556

PURPOSE: In familial adenomatous polyposis, genotype-duodenal phenotype correlations have not been clearly understood. We identified the adenomatous polyposis coli gene mutation in a family pedigree with severe duodenal adenomatosis. METHODS: Among 53 familial adenomatous polyposis families, we found a pedigree composed of five affected members with severe duodenal adenomatosis. Clinical manifestations of the family members were reviewed. The adenomatous polyposis coli gene of four members were screened by polymerase chain reaction-based single strand conformation polymorphism or protein truncation test. RESULTS: The family was characterized by sparse colorectal polyposis, osteomas, and epidermal cysts. However, there were intrafamilial variabilities in the occurrence of fundic gland polyposis, congenital hypertrophy of the retinal pigment epithelium, and desmoids. All the members had duodenal adenomatosis in their second or third decades, and the adenomatosis in three members progressed during surveillance. A frameshift mutation was found at codon 1556 of the adenomatous polyposis coli gene in two members, and the equivalent mutation was confirmed by protein truncation test in another two. CONCLUSIONS: Distal 3′ mutation of the adenomatous polyposis coli gene seems to contribute to severe duodenal adenomatosis in familial adenomatous polyposis. Specification of the adenomatous polyposis coli gene mutation may be a clue for surveillance strategy for duodenal adenomatosis in patients with familial adenomatous polyposis.