Background. Familial adenomatous polyposis is an autosomal dominant disease characterised by predisposition to colon polyposis and colorectal cancer and caused by germline mutations in the APC gene. The aim of the study was to establish the frequency of c.645+32C>T substitution in intron 5 of the APC gene in patients with multiple colon polyposis and in the general population and to determine if this substitution is a nonpathogenic polymorphism or a pathogenic mutation associated with multiple polyposis coli. Methods and Results. The frequency of c.645+32C>T substitution in the APC gene was established in 170 patients with the clinical phenotype of familial adenomatous polyposis or its attenuated form using denaturating gradient gel electrophoresis and direct sequencing. We tested a population of 200 noncancer persons using allelic specific polymerase chain reaction. The c.645+32C>T substitution was detected in 27 of 170 patients with multiple colon polyposis (i.e. 15.9%). The substitution was found in 32 of 200 control persons, i.e. in 16%. The difference between patients with polyposis and the control group was not statistically significant (p = 0.979; chí-square test). Conclusions. Our results suggest that the c.645+32C>T substitution is a non-pathogenic single nucleotide polymorphism appearing in about 16% of the Czech population.

        Key words: familial adenomatous polyposis, APC gene, mutation, polymorphism