Familial adenomatous polyposis
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Familial adenomatous polyposis (FAP) is a rare inherited condition where the large intestine develops a number of precancerous polyps as a result of defect in the adenomatous polyposis coli (APC) gene, it also increases the risk of developing cancer. Most people get the gene from one of their parents. However, the genetic mutation happens naturally in 25–30% of each person.
FAP causes the colon and rectum to develop polyps. Additionally, the upper gastrointestinal tract, particularly the first part of the small intestine, is susceptible to the development of polyps. When the patient is in their 40s, the polyps in their colon and rectum could develop into cancer if left untreated.
Patients with FAP have a nearly 100% lifetime risk of colorectal cancer if they are not treated. The risk of colorectal cancer increases as the patient gets older. The large intestine must typically be surgically removed in order to prevent cancer in those with familial adenomatous polyposis. Duodenal polyps can also develop cancer, but they are typically treatable with close monitoring and routine polyp removal.
Symptoms
The primary symptom of FAP is the development of hundreds or even thousands of polyps in your colon and rectum, which often begin by your mid-teens. By the time you are in your 40s, the polyps certainly will turn into rectal or colon cancer.
Early-stage of colorectal cancer is usually asymptomatic until the disease has progressed to the late stage, but they may include:
- Rectal bleeding, dark stool, or blood in stool
- A constant change in the bowel habit such as diarrhea or constipation
- Abdominal pain
- Unexplained weight loss
- Fatigue
In addition to FAP, abnormalities in other area of the body may indicate the presence of FAP. These may include:
- Dental abnormalities (unerupted teeth)
- Cyst of the skin
- Lump on bone of legs, arms, and skull
Causes
The APC gene has mutations that affect how well the gene’s protein is supposed to work, which is the cause of the disease. Cells are more likely to develop into cancer as a result of this unregulated cell growth. A mutation in APC was typically passed down from a parent who also had FAP to the majority of patients. A gene abnormality that is typically inherited from a parent is the cause of familial adenomatous polyposis. However, some people are born with the disease-causing gene anomaly.
15% of FAP patients develop desmoid tumors, which are fibrous tissue overgrowths that are rare condition. Sometimes hard, white sheets of desmoid tissue form and cause issues without becoming a tumor. They typically develop inside the abdomen after an abdominal operation and tend to surround the arteries (blood vessels) leading to the colon. This makes their removal challenging or impossible unless a significant portion of the small bowel is also removed. Desmoid tumors frequently recur even after removal. The second most frequent cause of mortality in FAP patients is desmoid disease.
Risk factors
The primary risk to develop familial adenomatous polyposis (FAP) is when someone from the family have this condition such as the parent, or siblings.
Diagnosis
A frequent screening program should begin early in the childhood if the patient is at risk. During yearly checkups, polyp development that is not yet malignant can be found.
- Screening
- Computed tomography (CT) scan or magnetic resonance imaging (MRI): This procedure will provide an image of the abdomen and the pelvic area. This imaging test could also be used to properly evaluate desmoid tumors.
- Sigmoidoscopy: To examine the rectum and sigmoid colon, a flexible tube is insert into your rectum. It is recommended to have an annual sigmoidoscopies starting at age 10 to 12 for those who have been genetically diagnosed with FAP or for those who have family members at risk but have not had genetic testing.
- Colonoscopy: To examine the entire colon, a flexible tube is insert into your rectum. Once colon polyps are identified, you must undergo an annual colonoscopy until your colon is surgically removed.
- Esophagogastroduodenoscopy (EGD): The stomach, esophagus, and upper small intestine are all examined using this type of screening procedure. Healthcare provider could also conduct a biopsy during this procedure by taking a small tissue sample.
- Genetic testing: If someone have the defective gene that causes FAP, a simple blood test can reveal this. They might be able to tell if someone is at risk for FAP issues through genetic testing. Healthcare provider could advise genetic testing if they have a family member that had been diagnosed with FAP. Saving children at risk from years of screening and emotional hardship is one benefit of eliminating FAP. Children who do have the gene have a significantly lower risk of developing cancer with the right screening and care.
- Other test: When FAP is diagnosed, or when the patient is in the middle of their adolescent years, the thyroid is examined annually using an ultrasound scan. Other test will also be recommended to assess and evaluate for any other medical problems that may develop upon having FAP.
Treatment
Healthcare provider will initially remove any small polyps discovered during the colonoscopy procedure. Usually by the late teens or early 20s, the polyps will accumulate to a point where they are too many to remove one by one. To stop colon cancer, patient will then be required to have surgery. A polyp that is malignant will also require surgery.
- Colorectal minimally invasive surgery: A few tiny incisions that only need one or two stitches to seal may be used by the surgeon to execute the surgery laparoscopically. The recovery time will likely be accelerated in regard to this less invasive procedure.
Patient might have one of the following procedures to have all or a portion of your colon removed, depending on your circumstances:
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- Subtotal colectomy with ileorectal anastomosis: Rectum is left untouched.
- Total proctocolectomy with a continent ileostomy: Surgery that involves the removal of the colon and rectum and the creation of an opening (ileostomy), typically on the right side of your abdomen.
- Total proctocolectomy with ileoanal anastomosis: (also known as J-pouch surgery), which involves attaching a portion of the small intestine to the rectum after the colon and rectum are removed.
- Follow-up treatment: Surgery does not necessarily cure FAP. The sections of the colon, stomach, and small intestine that are still in place or that have been rebuilt can still develop polyps. Endoscopic removal of the polyps might not be sufficient to lower the risk of cancer depending on their quantity and size. Additional surgery might be recommended.
Following colorectal surgery, the patient will require routine monitoring for familial adenomatous polyposis complications and, if necessary, treatment. The doctor may recommend extra therapy for the following conditions based on the screening results:
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- Duodenal polyps and periampullary polyps: Due to the possibility of these types of polyps developing into cancer, a healthcare provider may advise surgery to remove the upper portion of the small intestine (duodenum and ampulla).
- Desmoid tumors: Nonsteroidal anti-inflammatory medicines, anti-estrogens, and chemotherapy may all be prescribed to the patient. However, surgical procedure might still be recommended.
- Osteomas: Healthcare providers will recommend to surgically remove these noncancerous bone tumors for any cosmetic reasons and pain relief.
