The most common familial syndromes are hereditary breast and ovarian cancers (BRCA1 and BRCA2 mutations) (14), Li-Fraumeni Syndrome (TP53), hereditary pancreatitis (PRSS1, SPINK, and — rarely — CFTR mutation) (15–18), Peutz–Jeghers syndrome (STK11/LKB mutation) (19, 20), hereditary nonpolyposis colorectal cancer (HNPCC) caused by germline mutations in DNA mismatch repair genes (MSH2, MLH1, PMS1, PMS2 and MSH6/GTBP) (21, 22), ataxia telangiectasia (ATM), and familial atypical multiple mole melanoma syndrome (p16/CDKN2A mutation) (8, 23, 24). This evidence concerns the gene PMS2 and hereditary nonpolyposis colon cancer.