Among the known or classic CRC related genes (APC, AXIN2, BMPR1A, CHEK2, EPCAM, GREM1, MLH1, MSH2, MSH3, MSH6, MUTYH, NTHL1, PMS2, POLD1, POLE, PTEN, RPS20, SMAD4, STK11 or TP53 gene) mismatch repair (MMR) genes disease-causing variants were the most prevalent (16/20) in our cohort, accounting for 80.0% of all cases. The gene discussed is MLH1; the disease is colorectal carcinoma.