The result suggests that the number of colorectal polyps in FAP patients may be associated with a difference in the stability or biological function of the truncated APC protein.
We conclude that mutations in exons 1 to 6 of the APC gene are infrequent in patients with familial colorectal cancer who do not have many colorectal polyps.
No precise correlation between genotype and phenotype was observed, although a MSH2 missense (Thr905Arg) mutation was associated with a susceptibility to multiple colorectal polyps.
FAP is caused by mutations in the APC gene and various genotype-phenotype relationships have been defined including reports that colorectal polyposis is less severe with mutations 5' to codon 157 and that the risk of desmoid tumours is high in FAP patients with APC gene mutations between codons 1444 and 1598.