Variable Phenotype of a Pedigree of Attenuated Familial Adenomatous Polyposis (AFAP)

Abstract

A proband, 42 year old male patient with positive fecal occult blood test, was found to have multiple adenomas in the entire colon by both barium enema and colonoscopic examinations. Total colectomy with ileorectal anastomosis was performed under the diagnosis of familial adenomatous polyposis. Genetic analysis was carried out, revealing insertion of adenin at codon 158 in exon 4 of APC gene, causing nonsense mutation. Genetic diagnosis of AAPC was made. Genetic analysis of pro band's parents was also carried out, elucidating that the mother at the age of 68 had identical mutation of APC gene. She has no past history of colorectal cancer, however, very few tubular adenomas were found by subsequent colonoscopy. Pro band's father is not a mutation carrier. AFAP is a clinical phenotype and it varies. This indicates that prophylactic surgery is not an appropriate treatment option in some of the AFAP cases. Key words : familial adenomatous polyposis, APC gene, genetic diagnosis, phenotype, prophylactic total proctocolectomy.