Oncologic surveillance for subjects with biallelic mismatch repair gene mutations-10 year follow-up in a kindred

Background Lynch syndrome (LS) is caused by heterozygous germline mutations in the DNA mismatch repair (MMR) genes and is a highly penetrant autosomal dominant condition. A novel childhood cancer syndrome caused by biallelic germline MMR gene mutations and characterized by brain tumors, leukemias, gastrointestinal (GI) polyposis, GI cancer and café-au-lait spots (CALS) has been described. We reported the first biallelic kindred in which 2 of 3 siblings proven to have a homozygous germline MLH1 mutation, developed early-onset GI cancer. In contrast to LS with clear GI screening and surveillance recommendations, there are no recommendations for surveillance of individuals with biallelic mutations and no literature describing the long term outcome.