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Constitutional MisMatch Repair Deficiency (CMMRD)

Constitutional MisMatch Repair Deficiency (CMMRD)

OMIM number: 276300

Comments closing date: 27/03/2020

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Constitutional MisMatch Repair Deficiency (CMMRD) is a rare condition which predisposes children to multiple types of cancers during childhood. It is also linked to other features such as pigmentation on the skin including café au lait patches and freckling on the underarms. They can also suffer from brain malformations. People with CMMRD are born with two mutations in one of four genes. These genes are known as the “mismatch repair genes,” which include MLH1, MSH2, MSH6, and PMS2. When the mismatch repair genes are working properly, they help correct our DNA to prevent the formation of cancer. People who are born with only one mutation in one of these genes have a hereditary predisposition to adult-onset colorectal, endometrial, and other cancers called Lynch syndrome. Lynch syndrome is already licenced for PGD by the HFEA. However, if a person has mutations in both of the same mismatch repair gene, they will be affected by CMMRD. CMMRD can cause multiple cancers at a very young age, usually childhood or early adulthood. Common cancers include blood cancers (leukaemia and lymphoma), brain cancers (such as glioma), and cancers of the gastrointestinal tract. Cancer development has been recorded between the ages of 6 months to 39 years, with an average age of between 6 and 10 years of age. Due to the nature of these cancers, this condition is usually very life-limiting. Cancer treatment for these children is often not curative.

Review date: 26 February 2022