Familial Adenomatous Polyposis (FAP)
Description
Familial Adenomatous Polyposis (FAP) is a rare genetic disorder characterized by the development of hundreds or even thousands of polyps in the colon and rectum. These polyps have a high risk of transforming into colorectal cancer, making early detection and management crucial. This blog post will delve into the details of FAP, including its causes, symptoms, diagnosis, management, and how individuals can thrive with this condition.
Genes Involved
FAP is caused by mutations in the APC (Adenomatous Polyposis Coli) gene. This gene plays a crucial role in regulating cell growth and division. Mutations in the APC gene disrupt this regulation, leading to uncontrolled cell growth and the development of polyps. Other genes that can cause FAP are:
- MUTYH: This gene helps repair DNA damage. Mutations in MUTYH can increase the risk of colorectal cancer, particularly in individuals with a family history of FAP.
Recognizing the Signs and Symptoms
The primary symptom of FAP is the presence of numerous polyps in the colon and rectum. These polyps are usually asymptomatic in the early stages but can cause various symptoms as they grow and become more numerous. Common symptoms include:
- Blood in the stool
- Diarrhea
- Abdominal pain or cramping
- Changes in bowel habits
- Rectal bleeding
- Weight loss
- Fatigue
In some cases, individuals with FAP may also develop extraintestinal manifestations, such as:
- Osteomas (noncancerous bone growths) in the skull and jaw
- Dental abnormalities
- Desmoid tumors (benign fibrous tumors)
- Duodenal adenomas (polyps in the small intestine)
- Brain tumors
- Skin abnormalities
Causes
FAP is an inherited genetic disorder. Individuals with FAP inherit a mutated APC gene from one of their parents. This means that there is a 50% chance that each child of an individual with FAP will inherit the mutated gene and develop the condition. In rare cases, FAP can arise due to a spontaneous new mutation in the APC gene.
Inheritance/recurrence risk
FAP follows an autosomal dominant inheritance pattern. This means that a single copy of the mutated APC gene is sufficient to cause the condition. If one parent has FAP, there is a 50% chance that their child will inherit the mutated gene and develop the condition. If both parents have FAP, the chances of their child inheriting the condition increase to 75%.
