Familial adenomatous polyposis (FAP)

What are polyps? Polyps are abnormal tissue growths that appear like a small, and flat
bumps or like a tiny mushroom stalks. Most common polys are colon polyps.

“Does this colon polyps are cancerous, how can it be detected, does if I have a family
member affected am I at risk of having it?” – These questions may be wondering you.

Yes, these colon polyps can be cancerous and run within the family, and the condition is
termed as Familial Adenomatous Polyposis (FAP). Where F – familial represents a condition
running within the family, A – Adenomatous representing ‘Adenoma – benign tumour’,
adenomatous is a type of polyps in the colon/ small intestine that can turn cancerous, and P –
Polyposis represents a condition of having lots of colon polyps.

FAP individual develops a numerous number of polyps in the colon, at an early stage of life
may be in around teens, if these colon polyps are not treated it can develop into cancer. The
average age for developing colon cancer in FAP individuals is 39 yrs*.

But there is a condition in which the average age for developing colon cancer in FAP
individuals is 55 years, where this condition is termed as Attenuated Familial Adenomatous
Polyposis (AFAP)*.

But, all polyposis are not cancerous. The noncancerous polyps are termed as desmoid
tumours. Where your doctor can prescribe you for the removal of such desmoid tumors.
Though after removal, this desmoid tumors can grow again post-surgery. Many benign and
malignant tumors in both FAP and AFAP individuals it is found to occur in other parts of the
body also, such as the duodenum, stomach, skin, bones, and other tissues.

FAP is a rare genetic disorder that take place due to the presence of APC gene mutations.
APC stands for adenomatous polyposis coli. APC gene mutation is linked with FAP, AFAP,
Gardner syndrome, and Turcot syndrome. Colon polyposis individuals are also found to have
two mutations in the MUTYH gene, also known as MYH gene associated with MUTYH-
Associated Polyposis (MAP).

FAP is said to pass down within generations mostly in an autosomal dominant pattern of
inheritance that is an effected person pass down the mutated gene to the next generation
where the APC gene mutation is passed on. Though family with MUTYH gene mutation FAP
or AFAP, the pattern of inheritance is an autosomal recessive pattern that each parent carries
a copy of the mutated gene, but do not show any signs or symptoms of the condition*.
But how do you diagnose whether the condition of colon polyps within your family is
Familial Adenomas Polyposis or not? You can undergo genetic analysis by a DNA
sequencing, which would be carried out on your blood sample. Although the genetic tests
would not confirm the condition to be cancer or polyps themselves.

Myriad myRisk would provide you with the genetic testing analysis through DNA
sequencing, where it would detect the genes for FAP, along with which are covered in 35
gene panel that recognise inheritance risk of 8 cancers such as Breast, Ovarian, Colorectal,
Uterine, Melanoma, Gastric, Pancreatic, and Prostate.

References
* “Familial Adenomatous Polyposis (FAP): Inherited,” Cleveland Clinic. [Online].
Available: https://my.clevelandclinic.org/health/diseases/16994-familial-adenomatous-
polyposis-fap-inherited.
* C. N. E. Board, “Familial Adenomatous Polyposis,” American Society of Clinical
Oncology ® Cancer.Net, Doctor-Approved Patient Information, 2018. [Online].
Available: https://www.cancer.net/cancer-types/familial-adenomatous-polyposis.