Inheritance:

LS is caused by mutations (pathogenic variants) in the mismatch repair (MMR) gene, which includes MLH1, MSH2/EPCAM, MSH6, and PMS2. MMR is a DNA repair process in which the MMR proteins correct errors that occur during DNA replication. LS is an autosomal dominant condition. First-degree relatives of a mutation carrier have a 50% chance of also carrying the mutation. Any gender can inherit, and pass on, a mutation.

While rare, individuals with MMR mutations should be aware that if they have a child with another person who also has Lynch syndrome due to a mutation in the same gene, the child has a 25% chance of having Constitutional (or, Biallelic) Mismatch Repair Deficiency (CMMRD or BMMRD), characterized by brain, blood, gynecological, and certain pediatric cancers.