Familial Adenomatous Polyposis

Question 1

What is Familial Adenomatous Polyposis?

Answer 1

It is an autosomal dominant cancer predisposition syndrome caused by inherited mutations in the APC gene.
It is characterized by numerous adenomatous polyps form mainly in the epithelium of the large intestine.

Question 2

What variants are known to exist in FAP?

Answer 2

FAP and attenuated FAP (originally called hereditary flat adenoma syndrome) are caused by APC gene defects on chromosome 5

,
while autosomal recessive FAP(or MYH-associated polyposis) is caused by defects in the MUTYH gene on chromosome 1.

Question 3

The second form of FAP, known as ………………. has the APC gene functional but slightly impaired.

Answer 3

attenuated familial adenomatous polyposis

Question 4

a large multifunction tumour-suppressing protein which acts as a “……………….”?

Answer 4

gatekeeper

Question 5

APC regulates β-catenin, a protein that plays a crucial role …………………………………………., but which left uncontrolled also gives rise to numerous cancer

Answer 5

in cell communication, signalling, growth, and controlled destruction

Question 6

What is Signs and Symptoms of FAP?

Answer 6

1- patients with this condition gradually develop hundreds to thousands of colorectal polyps . small abnormalities at the surface of the intestinal tract, especially in the large intestine including the colon or rectum.

2- These may bleed, leading to blood in the stool. If the blood is not visible, it is still possible for the patient to develop anemia due to gradually developing iron deficiency.

3- If malignancy develops, this may present with weight loss, altered bowel habit, or even metastasis to the liver or elsewhere.

FAP can also develop ‘silently’ in some individuals, giving few or no signs until it has developed into advanced colorectal cancer.

Question 7

What’s the function of APC gens?

Answer 7

regulates transcription, cell adhesion, the microtubular cytoskeleton, cell migration, crypt fission, apoptosis, and cell proliferation.

Question 8

Both alleles of APC must be ………. for adenoma formation.

Answer 8

inactivated

Question 9

The high frequency of somatic loss of function in the second APC allele defines FAP as an ……………………………….

Answer 9

autosomal dominant condition.

Question 10

Loss of functional APC usually results in?

Answer 10

high levels of free cytosolic β-catenin ; Free β-catenin migrates to the nucleus, binds to T-cell factor 4, and inappropriately activates gene expression.

Question 11

MAJOR PHENOTYPIC FEATURES

Answer 11

Age at onset: adolescence through mid-adulthood

• Colorectal adenomatous polyps
• Colorectal cancer
• Multiple primary cancers