Lynch Syndrome is inherited in an Autosomal Dominant (AD) inheritance pattern. This video, produced by the Genomics Education Programme, offers a simple explanation of AD inheritance and may be useful when explaining genetics to your patients.
Genomics Education Programme: autosomal dominant inheritance
Each person will pass 50% of their DNA onto their offspring. This means that more distant relations will share smaller amounts of DNA with a relative reducing the likelihood that they will share the same gene. This diagram represents the amount of shared DNA between generations.
First degree relatives are at 50% risk of inheriting Lynch Syndrome and are eligible for cascade testing. Ask if your patient has any family members that would benefit from cascade testing.
Genomics Education Programme: Presentation: Patient with suspected Lynch syndrome
Children are offered testing from the age of 18 years onwards. Lynch Syndrome is associated with early adult-onset cancers. Risk reducing interventions such as screening, prophylactic surgery and chemoprophylaxis are not recommended before this age so there would be no advantage to testing a child before they reach the age of consent. However, if a child under the age of 18 years is known to have a first degree relative with Lynch Syndrome, have a low threshold to investigate any symptoms of cancer. Lynch Syndrome UK have produced a Family Gene Kit which is designed to aid first conversations with children about Lynch Syndrome. This and other patient information booklets are available on request from their website.
Lynch Syndrome UK: order free Lynch Syndrome Information Booklet
If a relative chooses not to have genetic testing, they may still be eligible for regular screening colonoscopies depending on the family history. A summary of the British Society of Gastroenterology Guidance regarding this can be found on this GENotes article.
Genomics Education Programme: Presentation: Patient with a family history of bowel cancer