Classic Familial Adenomatous Polyposis

• Classic Familial Adenomatous Polyposis (CFAP) is an inherited genetic disorder.
• It is characterized by hundreds to thousands of adenomatous polyps in the colon and rectum.
• Individuals with CFAP face a nearly 100% lifetime risk of developing colorectal cancer without intervention.
• The condition is primarily caused by a mutation in the APC gene.
• Management typically involves prophylactic surgery to remove the colon and ongoing surveillance.

What is Classic Familial Adenomatous Polyposis (CFAP)?

Classic Familial Adenomatous Polyposis (CFAP) is an autosomal dominant inherited disorder, meaning a person needs to inherit only one copy of the mutated gene to develop the condition. It is defined by the presence of hundreds to thousands of adenomatous polyps, which are benign growths that have the potential to become cancerous, primarily throughout the colon and rectum. Without surgical intervention, individuals with CFAP have a nearly 100% lifetime risk of developing colorectal cancer, often at a relatively young age, typically by their 40s. The severity and onset of polyp development can vary, but the progression to cancer is almost inevitable.

The condition is part of a broader spectrum of FAP-related disorders, but the “classic” form is distinguished by the high number of polyps. Early diagnosis and proactive management are crucial for preventing the development of life-threatening colorectal cancer. Regular screening, often beginning in adolescence, is a cornerstone of managing individuals at risk or diagnosed with CFAP.

Symptoms and Causes of Classic Familial Adenomatous Polyposis

The presentation of Classic Familial Adenomatous Polyposis can vary, but certain indicators are common. Initially, individuals with CFAP may be asymptomatic, with polyps developing silently over time. As the polyps grow and multiply, familial adenomatous polyposis symptoms may begin to appear, often including rectal bleeding, changes in bowel habits such as diarrhea or constipation, abdominal pain, and unexplained weight loss. Beyond the colon, CFAP can also manifest with extracolonic features, which are signs and symptoms outside the large intestine. These may include:

• Desmoid tumors (fibrous growths, often in the abdomen)
• Osteomas (benign bone growths, particularly on the jaw or skull)
• Congenital hypertrophy of the retinal pigment epithelium (CHRPE), which are harmless pigmented lesions in the eye
• Dental abnormalities, such as supernumerary teeth or unerupted teeth
• Gastric or duodenal polyps in the upper gastrointestinal tract

The primary causes of classic familial adenomatous polyposis are mutations in the Adenomatous Polyposis Coli (APC) gene, located on chromosome 5. The APC gene is a tumor suppressor gene, meaning it normally helps control cell growth and prevent the formation of tumors. A mutation in this gene impairs its function, leading to uncontrolled cell proliferation and the development of polyps. Approximately 75-80% of CFAP cases are inherited from a parent who also carries the mutation, following an autosomal dominant pattern. The remaining 20-25% of cases arise from a spontaneous, or de novo, mutation in the APC gene in individuals with no family history of the condition. Genetic testing can confirm the presence of an APC gene mutation and is often recommended for individuals with a family history of CFAP or those presenting with characteristic symptoms.

Treatment Options for Classic Familial Adenomatous Polyposis

Given the nearly 100% risk of colorectal cancer, the management of Classic Familial Adenomatous Polyposis is primarily surgical and prophylactic. The main goal of familial adenomatous polyposis treatment options is to prevent cancer development by removing the affected colon and rectum. The timing of surgery is crucial and typically performed in late adolescence or early adulthood, once the polyp burden becomes significant or high-grade dysplasia is detected. Surgical approaches include:

• Total colectomy with ileorectal anastomosis (IRA): This procedure removes the entire colon, but leaves the rectum intact. The small intestine (ileum) is then connected to the remaining rectum. This option preserves rectal function but requires lifelong endoscopic surveillance of the remaining rectal segment due to the continued risk of polyp formation and cancer.
• Total proctocolectomy with ileal pouch-anal anastomosis (IPAA): This involves removing both the colon and the rectum. A pouch is created from the end of the small intestine (ileum) and connected to the anus, allowing for a more natural bowel movement. This option significantly reduces the risk of colorectal cancer but may be associated with more complex surgical recovery and potential functional issues.
• Total proctocolectomy with end ileostomy: In this procedure, both the colon and rectum are removed, and the end of the small intestine is brought through an opening in the abdominal wall to create a stoma, where waste is collected in an external pouch. This is typically reserved for cases where IPAA is not feasible or desired.

Beyond surgery, ongoing surveillance is critical. For those undergoing IRA, regular endoscopic examinations of the rectum are necessary. All patients, regardless of surgical type, require periodic upper endoscopy to monitor for polyps in the stomach and duodenum, which can also occur in CFAP. Chemoprevention, using non-steroidal anti-inflammatory drugs (NSAIDs) like celecoxib, may be considered as an adjunct therapy to reduce polyp burden or delay surgery in some cases, but it is not a substitute for surgical intervention. Genetic counseling is also an essential component of care, providing guidance to affected individuals and their family members regarding inheritance patterns, screening recommendations, and reproductive options. According to the Centers for Disease Control and Prevention (CDC), early and consistent screening, along with appropriate surgical intervention, is vital for improving outcomes in individuals with FAP.