APC germ-line mutations in southern Spanish patients with familial adenomatous polyposis: genotype-phenotype correlations and identification of eight novel mutations.

Familial adenomatous polyposis (FAP) is a disease characterized by the presence of hundreds of adenomatous polyps in the colon and rectum which, if not treated, develop into colorectal cancer. FAP is an autosomal dominantly inherited disorder caused by mutation in the APC gene. The aim of this study was to search for germ-line mutations of the APC gene in unrelated FAP families from southern Spain. By direct sequencing of all APC gene exons, we found the mutation in 13 of 15 unrelated FAP families studied. We identified eight novel mutations: 707delA (exon6), 730_731delAG (exon7), 1787C-->G and 1946_1947insG (exon14), 2496delC, 2838_2839delAT, 2977A-->T, and 3224dupA (exon15). Two patients presented de novo germ-line mutations. Genotype-phenotype correlations for extraintestinal and extracolonic manifestations were studied. Intrafamilial phenotypic variability was observed in two families with mutations in exon/intron boundary, probably due to alternative splicing.