Hereditary Cancer and Genetic Testing

General information for people with inherited MLH1 mutations

Both men and women can carry a mutation in the MLH1 gene.

Inherited mutations in the MLH1 gene are associated with Lynch syndrome. Other names for Lynch syndrome include Hereditary Nonpolyposis Colorectal Cancer (HNPCC) and Muir-Torre syndrome, which refers to a subset of Lynch syndrome in which people have an increased risk of developing rare skin tumors.

People with inherited MLH1 mutations have increased risk for many cancers but particularly cancers of the large intestine (the colon and the rectum) and uterus (endometrium). See our Cancer Risk section for more information.  There are guidelines for screening and prevention for certain cancers in people with an MLH1 mutation. Clinical trials may also be available for people who test positive for an MLH1 mutation. See our Risk Management section for more information about screening options in people with MLH1 mutations.

People with an inherited MLH1 mutation who have been diagnosed with cancer may qualify for specific treatments or clinical trials. Visit our Cancer Treatment section for more information about treatment for people with an MLH1 mutation.

Children who inherit a MLH1 mutation from both their mother and father can have a rare syndrome known as “constitutional mismatch repair deficiency (CMMRD),” which can cause high risks of various cancers in childhood and young adulthood. See our Other Considerations section for more information about this disease.

The name MLH1 stands for "MutL homolog 1." The gene is located on chromosome 3. The MLH1 gene protein plays an important role in repairing DNA damage.


If you are a person with an MLH1 mutation, you can find peer support through the following resources:

Last updated September 03, 2021