Familial Adenomatous Polyposis (FAP)
Familial adenomatous polyposis (FAP) is the growth of polyps in the colon and rectal epithelium. FAP is an autosomal dominant genetic disorder that can occur in the upper portion of the small intestine too. Polyps are extra tissues that grow throughout the wall of the colon. Adenomatous polyps range from a hundred to thousands in number spread across the colon that develops into colon cancer after the age of 40 years, or into some other kind of malignancy. FAP is treated only through surgery.
FAP is resultant of germ line mutation in the APC gene, mainly inherited and spontaneous in 25% of the cases. The gene mutation manifestation begins from pre-teen, with appearance of abnormal excessive tissue outgrowth called polyps; the number multiplies with time, spreading throughout the large intestine up to the duodenum and eventually turns into malignant tissues at a later stage. FAP can also lead to other serious complications like duodenal polyps, desmoids and more.
Duodenal Polyps :
The polyps that grow in the upper part of the large intestine and become malignant later; however, these can be detected and removed before they become cancerous.
Periampullary Polyps :
Ampulla is the area where the bile and pancreatic duct empties into the large intestine and polyps can occur in this region. Similar to the duodenal polyps, periampullary polyps can also be diagnosed and treated.
These are benign tissue mass that develop in any part of the body, often in the stomach portion; yet the desmoids cause grave consequence when found in the nerves and blood vessels, pressing against the neurons and obstructing blood supply; thus impairing an organ.
In addition to the above risks, in rare cases FAP syndrome can cause thyroid, liver, adrenal glands cancer or various other types of cancers; benign skin and bone tumours too. FAP syndrome can also lead to unnatural retinal pigmentation and dental complications.
Mostly the polyps silently develop in the colo-rectal canal. However, when the number of colo-rectal polyps increases with time, there is bleeding, which appears in stool or the patient becomes anaemic and lose weight. When the polyps become malignant and reach to an advanced stage, there are abnormal bowel habits and the cancer metastasizes to liver or any other digestive organ. Based on the extent of APC mutated gene inheritance, the polyps can manifest completely or express in an attenuated form; either entirely covering the colorectal region or develop only in the duodenal tract or in both. Thus, an absence of rectal polyps need not necessarily mean FAP is not manifested. Only a thorough colonoscopy can confirm the condition.
Once there is familial polyposis diagnosed in family, other closely related members are under the high-risk bracket of inheriting the gene and should be regularly screened for the condition and meticulously monitored. Colonoscopy and genetic testing are two of the most efficient methods to detect FAP condition. Once detected, a prophylactic colectomy is mandatory before 30 years of age to avert cancer. Prior to the cancerous stage is the most effective time to eliminate the polyps when they are localized and have not spread beyond the rectum and large intestine. The success rate of partial colectomy is high since the cancer causing location itself is removed. However, the recurrence of polyps is possible; thereby necessitating the need of a periodic surveillance of the remainder of the colon.