The most frequent inherited CRC syndromes are: i) familial adenomatous polyposis (FAP), due to mutations in the adenomatous polyposis gene (APC); ii) MUTYH-associated polyposis (MAP), presenting mutations in the MUTYH gene; iii) hereditary nonpolyposis colorectal cancer (HNPCC), due to mutations in a DNA mismatch repair gene, most frequently MLH1 or MSH2 and rarely MSH6 or PMS2 [3–6]. The gene discussed is MLH1; the disease is Familial adenomatous polyposis.