Cookies on this website

We use cookies to ensure that we give you the best experience on our website. If you click 'Accept all cookies' we'll assume that you are happy to receive all cookies and you won't see this message again. If you click 'Reject all non-essential cookies' only necessary cookies providing core functionality such as security, network management, and accessibility will be enabled. Click 'Find out more' for information on how to change your cookie settings.

AIM: The study aimed to describe genetical and clinical features of attenuated familial adenomatous polyposis (AFAP) and to propose clinical criteria and guidelines for treatment and surveillance. METHOD: A questionnaire study was carried out of polyposis registries with data on patients with presumed AFAP, defined as having ≤ 100 colorectal adenomas at age ≥ 25. RESULTS: One hundred and ninety-six patients were included. The median number of adenomas was 25 (0-100) with a uniform distribution of colorectal adenomas and carcinomas (CRC). Age at CRC diagnosis was delayed by 15 years compared with classic FAP. Eighty-two patients had a colectomy and an ileorectal anastomosis and 5/82 (6%) had a secondary proctectomy. The location of the mutation in the APC gene was known in 69/171 (40%) tested patients. Only 15/29 (52%) of mutations in APC were found in parts of the gene usually associated with AFAP (the 5' end, exon 9 and 3' end). CONCLUSIONS: A subset of FAP patients with a milder phenotype does exist and treatment and surveillance had to be modified accordingly. The mutation detection rate is lower than in classic FAP and mutations in AFAP patients are located throughout the APC gene. We propose the following clinical diagnostic criteria for AFAP: a dominant mode of inheritance of colorectal adenomatosis and <100 colorectal adenomas at age 25 or older. Colonoscopy had to be preferred to sigmoidoscopy and surveillance had to be life-long. In the majority of patients, prophylactic colectomy and ileorectal anastomosis are recommended at the age of 20-25 years.

Original publication




Journal article


Colorectal Dis

Publication Date





e243 - e249


Adenomatous Polyposis Coli, Adolescent, Adult, Aged, Aged, 80 and over, Child, Colectomy, DNA Mutational Analysis, Female, Genes, APC, Genetic Testing, Humans, Male, Middle Aged, Mutation, Registries, Statistics, Nonparametric, Young Adult