We designed customized MIPs for the coding regions of seven high-penetrance CRC susceptibility genes, i.e., APC, MLH1, MSH2, MSH6, PMS2, MUTYH and NTHL1 (POLE and POLD1 exonuclease domains were independently tested by Sanger sequencing), and evaluated the performance of these MIPs in the detection of genetically predisposed patients diagnosed before the age of 35. This evidence concerns the gene NTHL1 and colorectal carcinoma.