Discuss the inherited disorders familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer, their prevalence, responsible genes, and screening recommendations for those confirmed with the inherited gene. Use at least one scholarly source other than your textbook to connect your response to national guidelines and evidence-based research in support of your ideas.
Inherited disorders in the form of familial adenomatous polyposis (FAP) and hereditary nonpolyposis colorectal cancer (HNPCC) pose significant risks for the development of colorectal cancer. Understanding the prevalence, responsible genes, and screening recommendations for individuals with these inherited gene mutations is crucial for early detection and prevention strategies. This paper will discuss FAP and HNPCC, drawing on scholarly sources to align with national guidelines and evidence-based research.
FAP is an autosomal dominant disorder characterized by the presence of numerous adenomatous polyps in the colon and rectum. These polyps have a high risk of progressing to colorectal cancer if left untreated. The prevalence of FAP in the general population is estimated to be around 1 in 8,000 to 10,000 individuals (Kamangar & Dores, 2006). The responsible gene for FAP is the adenomatous polyposis coli (APC) gene. Mutations in this gene lead to the loss of control over cell growth, resulting in the development of polyps. The majority of individuals with FAP inherit the condition from an affected parent, but about 20% of cases occur due to new spontaneous mutations (Lynch, 2007).
HNPCC, also known as Lynch syndrome, is another inherited disorder associated with an increased risk of developing colorectal cancer. It is estimated that HNPCC accounts for approximately 2-4% of all colorectal cancer cases (Lynch, 2007). Unlike FAP, HNPCC is characterized by a few adenomatous polyps or even the absence of polyps. The responsible genes for HNPCC are mainly related to mismatch repair genes, including MLH1, MSH2, MSH6, and PMS2. These genes help repair errors in DNA replication, and mutations in any of these genes can lead to the accumulation of DNA replication errors and subsequent tumor development (Li, Jenkins, & Seo, 2020).
Screening recommendations for individuals with FAP and HNPCC vary and are based on national guidelines and evidence-based research. In the case of FAP, it is recommended that individuals undergo regular colonoscopies starting in their teenage years or early twenties (Lynch, 2007). This is to detect and remove any polyps before they progress to cancer. In addition to colonoscopies, genetic testing is also recommended to identify individuals at risk and guide screening and surveillance strategies (Burn et al., 2011). Annual surveillance of the duodenum through upper endoscopies is also recommended due to the increased risk of duodenal polyps and cancer in FAP patients (West et al., 2019).
For HNPCC, screening recommendations are focused on identifying individuals with Lynch syndrome and managing their colorectal cancer risk. The current guidelines suggest universal tumor testing in all individuals diagnosed with colorectal cancer, irrespective of age or family history (Li et al., 2020). This genetic testing helps to identify individuals with microsatellite instability (MSI) or loss of staining for the MMR proteins, indicating potential Lynch syndrome. If a pathogenic mutation is identified in one of the mismatch repair genes, then cascade testing of family members is recommended. Additionally, colonoscopic surveillance may commence at an earlier age in patients with identified Lynch syndrome mutations (Burn et al., 2011).
In conclusion, familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer are two inherited disorders associated with an increased risk of developing colorectal cancer. The responsible genes for FAP and HNPCC are the APC gene and mismatch repair genes, respectively. Screening recommendations for individuals with FAP include regular colonoscopies, genetic testing, and duodenal surveillance. On the other hand, for individuals with HNPCC, universal tumor testing and cascade testing of family members is recommended, along with earlier age commencement of colonoscopic surveillance. These recommendations are supported by national guidelines and evidence-based research to ensure the effective detection and prevention of colorectal cancer in individuals with inherited gene mutations.