Through germline whole exome sequencing of both affected individuals in our parent-child PMP family, we were able to assess and exclude the known colorectal cancer predisposing genes including APC, MLH1, MSH2, MSH6, PMS2, MUTYH, BMPR1A, SMAD4, POLE and POLD1, with the caveat that STK11 could not be excluded due to low coverage on exome sequencing. The gene discussed is MLH1; the disease is colorectal cancer.