Question

• Discuss the inherited disorders familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer, their prevalence, responsible genes, and screening recommendations for those confirmed with the inherited gene.

Answer 1

FAMILIAL ADENOMATOUS POLYPOSIS

Familial adenomatous polyposis is an inherited disorder which presents multiple adenomatous polyps in the colon.The patient will develop colon cancer if it is not treated.

Prevalence:

It is seen in both males and females.0.5% of colon cancers are due to familial adenomatous polyposis. According to the reports it has affected 50,000 American families and seen in 1-9 per 100,000 individuals.

Responsible genes:

The responsible gene is adenomatous polyposis coli (APC) gene.

Screening recommendations:

• By 34 years of age,polyps will be manifested in an individual with familial adenomatous polyposis.The children of an affected parent are at 50% risk for developing the disease.
• Sigmoidoscopy examinations should be done from 11 years of age.
• Prophylactic total colectomy should be suggested to prevent colon cancer.

HEREDITARY NON POLYPOSIS COLO RECTAL CANCER (HNPCC)

Hereditary non polyposis colorectal cancer or Lynch disease is a form of colorectal cancer which is caused by an abnormality in our body's DNA repairing gene.It increases the risk of endometrial cancer.

Prevalence:

130,000 cases of lynch disease are diagnosed every year in United States and is the most common form of cancer.Both men and women are equally affected.Between 1-in-500 and 1-in-1000 are affected with the disease.

Responsible genes:

Mutation in MLH1, MSH2, MSH6 or PMS2 gene.

Screening recommendations:

• Colonoscopy

Start colonoscopy at the age of 21 or if there are persons diagnosed with colorectal cancer in the family start 10 years earlier than the age of the youngest person diagnosed.Do screen every alternate year and after 40,screen every year.

• Trans vaginal ultra sound,pelvic examination

Start at 25-35 years of age and repeat it every year.

• Biopsy of the endometrium

It should be done when symptoms appears.

• Urine cytology

Start at 30 years if anyone in the family is diagnosed with ureter or renal pelvis cancer. Do screen every 2 years.