Muir-Torre Syndrome

Overview

What is Muir-Torre syndrome?

Muir-Torre syndrome is a variant of hereditary non-polyposis colorectal cancer (HNPCC). Cancer begins when normal cells begin to change and grow uncontrollably, forming a mass called a tumor. A tumor can be benign (noncancerous) or malignant (cancerous, meaning it can spread to other parts of the body). People with Muir-Torre syndrome have an increased risk of the types of cancer seen in HNPCC, including colorectal, endometrial (uterine), stomach, ovarian, small bowel (intestinal), urinary tract, and hepatobiliary (liver or bile duct) cancers. However, they are also at risk for developing certain skin changes in adulthood that may form in the sebaceous glands. The sebaceous glands are located just under the skin and produce and oily substance called sebum that is a part of sweat. The typical skin changes found in Muir-Torre syndrome are sebaceous adenomas, sebaceous epitheliomas, sebaceous carcinomas, and keratocanthomas. Most of these skin conditions are associated with noncancerous lumps on the skin, some of which are liquid-containing cysts. Basal cell carcinoma, a common type of skin cancer usually related to sun exposure, has also been reported in people with Muir-Torre syndrome. Only the skin carcinomas are cancerous.

What causes Muir-Torre syndrome?

Muir-Torre syndrome is a genetic condition. This means that the cancer risk can be passed from generation to generation in a family. Two genes have been linked to Muir-Torre syndrome, MLH1 and MSH2. A mutation (alteration) in either of these genes gives a person an increased lifetime risk of developing the types of cancer or benign skin changes listed above. Mutations in the MLH1 or MSH2 gene also cause HNPCC. It is possible that there may be other genes that play a role in Muir-Torre syndrome.

How is Muir-Torre syndrome inherited?

Normally, every cell has two copies of each gene: one inherited from the mother and one inherited from the father. Muir-Torre syndrome follows an autosomal dominant inheritance pattern, in which a mutation needs to happen in only one copy of the gene for the person to have an increased risk of getting that disease. This means that a parent with a gene mutation may pass along a copy of their normal gene or a copy of the gene with the mutation. Therefore, a child who has a parent with a mutation has a 50% chance of inheriting that mutation. A brother, sister, or parent of a person who has a mutation also has a 50% chance of having the same mutation.

How common is Muir-Torre syndrome?

Muir-Torre syndrome is considered to be rare.

How is Muir-Torre syndrome diagnosed?

Muir-Torre syndrome is diagnosed if a person has one or more of the skin changes and one or more of the internal cancers listed above. A person diagnosed with Muir-Torre syndrome can have a blood test to see if they have a mutation in the MLH1 or MSH2 genes. However, not everyone with Muir-Torre syndrome will have a detectable mutation in one of these two genes.

What are the estimated cancer risks associated with Muir-Torre syndrome?

The cancer risks are considered to be similar to the risks of people who have HNPCC
General cancer risks for people with Muir-Torre syndrome