Colorectal cancer is a rare disease in the pediatric age group and, when present, suggests an underlying genetic predisposition. The most common hereditary colon cancer susceptibility condition, Lynch syndrome (LS), previously known as hereditary nonpolyposis colorectal cancer, is an autosomal dominant condition caused by a germline mutation in 1 of 4 DNA mismatch repair (MMR) genes: MLH1, MSH2, MSH6, or PMS2. The mutation-prone phenotype of this disorder is associated with gastrointestinal, endometrial, and other cancers and is now being identified in both symptomatic adolescents with malignancy as well in asymptomatic mutation carriers who are at risk for a spectrum of gastrointestinal and other cancers later in life. We review the DNA MMR system, our present understanding of LS in the pediatric population, and discuss the newly identified biallelic form of the disease known as constitutional mismatch repair deficiency syndrome. Both family history and tumor characteristics can help to identify patients who should undergo genetic testing for these cancer predisposition syndromes. Patients who carry either single allele (LS) or double allele (constitutional mismatch repair deficiency syndrome) mutations in the MMR genes benefit from cancer surveillance programs that target both the digestive and extraintestinal cancer risk of these diseases. Because spontaneous mutation in any one of the MMR genes is extremely rare, genetic counseling and testing are suggested for all at-risk family members.
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*Department of Pediatrics, Division of Gastroenterology, Hepatology, and Nutrition, University of California, San Diego
†Department of Pediatrics, Division of Gastroenterology/Hepatology and Nutrition, Hospital for Sick Children, University of Toronto, Toronto, Canada
‡Division of Gastroenterology, Hepatology, and Nutrition, Nationwide Children's Hospital, Columbus, OH.
Address correspondence to Steven H. Erdman, MD, Division of Gastroenterology, Hepatology, and Nutrition, Nationwide Children's Hospital, 700 Children's Drive, Columbus, OH 43205-2664 (e-mail: email@example.com).
Received 29 July, 2013
Accepted 11 September, 2013
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S.H.E. discloses grant funding from Cancer Prevention Pharmaceuticals for the study of hearing status in children and adolescents with familial adenomatous polyposis. This support is not relevant to this article. The other authors report no conflicts of interest.