Genotype-phenotype correlations were found in carriers of APC mutations but not in carriers of biallelic MYH mutations, except for a negative correlation with low number of polyps.
Mutation at the 5'-end of APC (codons 144-232), mutation of MYH and unknown APC or MYH mutation were correlated with a low number of polyps both at presentation and follow-up.
Thus, MUTYH mutation testing may be a reasonable cascade test in early onset CRC found to have proficient DNA mismatch repair, regardless of pattern of family history or number of polyps.
The detection of almost exclusively G:C-->T:A transversions in the K-ras gene of HPs/SSAs strongly suggests that these polyps are related causally to MYH deficiency.
For phenotype/genotype correlation, patients aged more than 35 years at the time of colectomy and with fewer than 100 polyps had significantly more mutation found on MYH.
No biallelic mutations of MYH gene were detected in colorectal cancer patients and in patients with small number (<5) of polyps without colorectal cancer.
APC and MUTYH mutation prevalence was evaluated by polyp burden; the clinical characteristics associated with a pathogenic mutation were evaluated using logistic regression analyses.
Finally, MYH-associated polyposis is caused by mutations in the MUTYH gene and is inherited in an autosomal recessive manner but may or may not be associated with polyps.
Our results show that somatic molecular markers of polyps can be useful in identifying MAP cases and support the need for the complete MUTYH gene analysis only in patients heterozygous for recurrent variants.
Biallelic MUTYH PVs were identified in 82 individuals (representing 0.2% of tested individuals) with most (75/82; 91.5%) reporting a personal history of CRC and/or polyps.