MYH associated polyposis: severe phenotype in the homozygosity for the 1103delC mutation.

MYH-associated polyposis (MAP) is an autosomal recessive disease associated with multiple colonic adenomas and colorectal cancer. Y165C and G382D MYH missense mutations are involved in more than 80% of cases in Caucasians and the large series published do not include patients homozygous for other mutations. We present the report of two siblings homozygous for the nonsense frameshift mutation 1103delC. The proband aged 28 presented with four colonic adenocarcinomas and 20-30 synchronous adenomas. Her sister aged 24 had 20 colonic adenomas and a severe Spigelman's III duodenal adenomatosis. Their parents, aged 60 and 51, heterozygous for the 1103delC MYH mutation, presented 5 and 2 low risk colorectal adenomas, respectively.