Familial Adenomatous Polyposis
Familial adenomatous polyposis (FAP) is a serious genetic disease that poses significant risks to the carrier’s life. It occurs in about one in 10,000 humans.
The cause of the disease is genetically inherited disorder of the so-called APC gene. This gene belongs into the group of “tumor suppressor genes” as it is responsible for proper cell division and cell cycle maintenance. Damaged APC gene increases the risk of uncontrolled cell proliferation and development of a malignant disease, especially colorectal carcinoma.
Congenital mutation of the APC gene has severe consequences in the large intestinal mucosa. The cell proliferation is increased and tens, hundreds or even thousands polyps develop from the intestinal mucous membrane. These polyps are benign (i.e. non-malignant). However, there is a virtually one hundred percent chance that one or more polyps will transform into a malignant colorectal cancer. This happens in a relatively young age, often before 30 years of life. The polyps may be located not only in the large intestine but often in small intestine including the duodenum and in the stomach. The fragile polyps tend to bleed and cause blood in stool occurrence and sometimes even anemia. Large polyps can obstruct the inside of the intestine and cause an acute intestinal obstruction.
The affected people have also increased risk of other malignant tumors occurrence such as malignant thyroid tumors, liver tumors, brain tumors, kidney tumors and multiple benign bone tumors and benign tumors of the subcutaneous tissue. APC mutation together with presence of intestinal polyps and development of any extraintestinal manifestations is known as the Gardner’s syndrome.
The polyps can be diagnosed by a colonoscopy. Colonoscopy allows evaluating the number of polyps, to take a biopsy from suspicious locations and perform a polypectomy (polyp removal). Polyps in the upper part of the gastrointestinal tract may be treated similarly by the upper GI endoscopy. It is advisable to exclude the presence of other tumors by imaging methods such as abdominal ultrasound and computed tomography. The APC gene mutation can be confirmed by genetic analysis. It is necessary to determine whether some other family member have similar problems, because this genetic disease tends to affect the relatives.
The polyps can be removed by polypectomy during a colonoscopy. However, more severe forms of familiar adenomatous polyposis have often present hundreds or thousands polyps and this number can not be solved endoscopically. The ultimate solution is the surgical interventions with removal of the whole large intestine. The rectum is either left intact (and then it must be regularly endoscopically checked) or removed as well. When the rectum is removed, it is possible to create a colostomy or more favorably an ileo-anal pouch.