Muir-Torre syndrome

Muir-Torre syndrome is a subtype of Lynch syndrome and may be caused by changes (mutations) in either the MLH1, MSH2, or MSH6 gene.^[1][2] These genes give the body instructions to make proteins needed for repairing DNA. The proteins help fix mistakes that are made when DNA is copied before cells divide. When one of these genes is mutated and causes the related protein to be absent or nonfunctional, the number of DNA mistakes that do not get repaired increases substantially. The affected cells do not function normally, increasing the risk of tumor formation. The MSH2 gene is responsible for MTS in the majority of cases.^[3][4] Mutations in MLH1 and MSH2 have the most severe effect.^[2]

Not everyone diagnosed with MTS will have a detectable mutation in one of these genes.^[5] Other, unidentified genes may also play a role in the development of the condition.

Muir-Torre syndrome (MTS) is a genetic (typically inherited) condition in which mutations in specific genes significantly increase a person's risk to develop the skin changes and cancers associated with the condition. Once a person has a genetic predisposition to developing cancer, environmental factors can "trigger" the development of certain cancers (as is generally the case with all hereditary cancer predisposition syndromes). To our knowledge, there is no evidence that exposure to herbicides may be directly responsible for causing MTS.

Muir-Torre-syndrome (MTS) is a variant of Lynch syndrome and is inherited in an autosomal dominant manner. This means that having only one changed (mutated) copy of the responsible gene in each cell is enough for a person to develop the condition. When a person with an autosomal dominant condition has children, each child has 50% (1 in 2) chance to inherit the mutated copy of the responsible gene. It is important to note that people who inherit a mutated gene that causes MTS inherit an increased risk of cancer, not the disease itself. Not all people who inherit a mutation in an associated gene will develop cancer. This phenomenon is called reduced penetrance.

The majority of people diagnosed with a form of Lynch syndrome have inherited the mutated gene from a parent. However, because not all people with a mutation develop cancer, and the variable age at which cancer may develop, not all people with a mutation have a parent who had cancer.^[6] Thus, the family history may appear negative. A positive family history of MTS is identified in roughly 50% of affected people.^[3] The percentage of people with Lynch syndrome who have a new mutation in the gene that occurred for the first time (and was not inherited from a parent) is unknown but is estimated to be extremely low.^[6]