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.

BACKGROUND: Familial adenomatous polyposis (FAP) is characterised by variable phenotypic expression. Part of this is attributable to a relationship between APC genotype and phenotype but there remains significant intrafamilial variation. In the Min mouse model of FAP, differences in the severity of gastrointestinal polyposis result from the action of modifier genes. AIMS: To determine whether phenotypic variation in human FAP has an inherited component consistent with the action of modifier genes. METHOD: We systematically examined polyp numbers in colectomy specimens from patients with classical FAP. Variation both between and within families was analysed. Formal modelling of the segregation of disease severity in families was performed RESULTS: There was strong evidence for a relationship between site of mutation and the number of colorectal polyps, with germline mutations in the "cluster region" causing the most severe disease and those with mutations between codons 1020 and 1169 having the mildest disease. In addition to this genotype-phenotype relationship, we found evidence for non-APC linked genetic modifiers of disease expression. First degree relatives had more similar polyp counts than more distant relatives. Formal modelling of the segregation of disease severity in families revealed further evidence for the action of modifier genes, with a best fit to a mixed model of inheritance. CONCLUSION: Our data provide good evidence to support the hypothesis that modifier genes influence the severity of FAP in humans.

Original publication

DOI

10.1136/gut.51.3.420

Type

Journal article

Journal

Gut

Publication Date

09/2002

Volume

51

Pages

420 - 423

Keywords

Adenomatous Polyposis Coli, Adolescent, Adult, Colonic Polyps, Female, Genes, APC, Genotype, Germ-Line Mutation, Humans, Male, Pedigree, Phenotype, Severity of Illness Index