HERIDETARY NON-POLYPOSIS COLORECTAL CANCER - LYNCH SYNDROME

Question 1

Inheritance

Answer 1

Autosomal dominant

Question 2

Mutation

Answer 2

Mutation in DNA mismatch repair gene (MSH2, MSH6, MLH1, PMS2) resulting in microsatellite genomic instability and subsequent mutations

Question 3

Prognosis (3)

Answer 3

• Over half develop CRC, onset in fourth decade
• Accelerated progression from adenoma to CRC. Increased risk several extracolonic malignancies; endometrial is commonest
• Usual history of 3 family members, 2 generations, 1 premature (before 50)

Question 4

Lynch Syndrome I

Answer 4

Patients without multiple polyps who develop predominantly right sided colon cancer at a young age

Question 5

Lynch Syndrome II

Answer 5

Same as Lynch I but additional risk of extracolonic adenocarcinomas of the uterus, ovary, cervix, and breast

Question 6

Screening

Answer 6

Start screening at age 25 with colonoscopy every 1 to 2 years