What is the definition of Muir-Torre Syndrome?
Muir-Torre syndrome (MTS) is a form of Lynch syndrome and is characterized by sebaceous (oil gland) skin tumors in association with internal cancers. The most common internal site involved is the gastrointestinal tract (with almost half of affected people having colorectal cancer), followed by the genitourinary tract. Skin lesions may develop before or after the diagnosis of the internal cancer. MTS is caused by changes (mutations) in the MLH1 or MSH2 genes and is inherited in an autosomal dominant manner. A mutation in either of these genes gives a person an increased lifetime risk of developing the skin changes and types of cancer associated with the condition.
What are the alternative names for Muir-Torre Syndrome?
- Cutaneous sebaceous neoplasms and keratoacanthomas multiple with gastrointestinal and other carcinomas
What are the causes for 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. 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. Mutations in MLH1 and MSH2 have the most severe effect.
Not everyone diagnosed with MTS will have a detectable mutation in one of these genes. Other, unidentified genes may also play a role in the development of the condition.
What are the symptoms for Muir-Torre Syndrome?
Sebaceous adenoma is the most characteristic finding in people with Muir-Torre syndrome (MTS). Other types of skin tumors in affected people include sebaceous epitheliomas, sebaceous carcinomas (which commonly occur on the eyelids) and keratoacanthomas. Sebaceous carcinoma of the eyelid can invade the orbit of the eye and frequently metastasize, leading to death. Tumors at other sites can also metastasize, but are less likely to cause death. Common sites of keratocathomas include the face and the upper side of the hands, but they can occur anywhere on the body.
The most common internal cancer in people with MTS is colorectal cancer, occurring in almost half of affected people. The second most common site is the genitourinary tract. Other cancers that may occur include breast cancer, lymphoma, leukemia (rarely), salivary gland tumors, lower and upper respiratory tract tumors, and chondrosarcoma. Intestinal polyps as well as various benign tumors may also occur.
What is the outlook (prognosis) for Muir-Torre Syndrome?
About 60% of people with MTS develop metastatic disease. Prognosis may depend on the associated internal cancer(s) each affected person has. People with MTS should have regular screening examinations, particularly of the gastrointestinal and genitourinary tracts.
How is Muir-Torre Syndrome diagnosed?
A person is suspected to have Muir-Torre syndrome (MTS) if he/she has one or more of the following:
- History of one or more sebaceous tumors
- Age younger than 60 years at first presentation of sebaceous tumors
- Personal history of Lynch-related cancers
- Family history of Lynch-related cancers
The presence of specific skin tumors in MTS may lead to the correct diagnosis even in the absence of a clear family history. A person diagnosed with MTS can also have genetic testing to see if they have a mutation in one of the genes known to cause MTS. However, not everyone with Muir-Torre syndrome will have a detectable mutation in one of these genes. Other, unidentified genes may also play a role in the development of the condition.
Is Muir-Torre Syndrome an inherited disorder?
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. Thus, the family history may appear negative. A positive family history of MTS is identified in roughly 50% of affected people. 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.