Lynch syndrome, also known as hereditary nonpolyposis colorectal cancer (HNPCC), is an autosomal dominant genetic disorder characterized by an increased risk of developing colorectal cancer and other malignancies. It is the most common inherited syndrome associated with colorectal cancer, accounting for approximately 3-5% of all cases of this disease. The pathogenesis of the syndrome is due to mutations in the genes of the DNA mismatch repair system (MMR), which leads to microsatellite instability and an increased frequency of mutations in cells. The clinical picture is characterized by early development of colorectal cancer (usually before the age of 50), predominant localization of tumors in the right half of the colon, and a high risk of developing extra-colorectal malignancies.
History of the disease and interesting historical facts
The disorder was first described by Dr. Henry Lynch in 1966, when he discovered a familial cluster of colorectal cancer cases in a single family. Interestingly, the syndrome was initially mistaken for familial adenomatous polyposis due to the similarity of clinical manifestations. In the 1990s, advances in molecular genetics identified the specific mutations responsible for the syndrome. “The discovery of the molecular mechanisms of Lynch syndrome was a turning point in our understanding of hereditary predisposition to colorectal cancer,” notes Dr. Jonathan Lunsford of the Memorial Sloan-Kettering Cancer Center.
Epidemiology
According to the International Agency for Research on Cancer (IARC), the incidence of Lynch syndrome is approximately 1:440 in the general population. In the structure of hereditary colorectal cancer, this syndrome occupies a leading position, accounting for 70-80% of all cases. Statistics show that the risk of developing colorectal cancer in mutation carriers reaches 80% by the age of 70. The average age of diagnosis of colorectal cancer in Lynch syndrome is 44-45 years, which is significantly lower than in sporadic forms of the disease (median 69 years).
Genetic predisposition to this disease
The main genes whose mutations are associated with the development of Lynch syndrome are MLH1, MSH2, MSH6, PMS2 and EPCAM. The most frequently affected genes are MLH1 (50% cases) and MSH2 (40%). A feature of the mutations is their high penetrance - the probability of developing colorectal cancer in the presence of a mutation is 52-82%. At the same time, mutations in the MSH6 gene are characterized by a later onset of the disease and a slightly lower risk of developing cancer compared to other genes of the MMR system.
- What genes are most commonly mutated in Lynch syndrome? The main mutant genes are MLH1 and MSH2, which together account for approximately 90% of all cases.
- How is the disease transmitted? Lynch syndrome is inherited in an autosomal dominant manner, meaning there is a 50% chance of passing the mutation on to each child.
Risk factors for the development of this disease
In addition to genetic predisposition, there are additional factors that contribute to the development of the disease. Among them are chronic intestinal inflammation, smoking, alcohol abuse, and dietary characteristics high in red meat. Studies show that exposure to ionizing radiation can worsen the course of the disease in carriers of mutations. It has also been established that folate deficiency can enhance the effect of mutations in the genes of the MMR system.
Diagnosis of this disease
The diagnostic process includes a comprehensive examination of the patient. The main symptoms include the presence of colorectal cancer at a young age, multiple or bilateral tumors, and a family history of colorectal cancer. Laboratory diagnostics are based on the detection of microsatellite instability and immunohistochemical analysis of MMR system proteins. Radiological studies include colonoscopy with biopsy of suspicious areas. For differential diagnosis, it is necessary to exclude other hereditary syndromes, such as familial adenomatous polyposis and MUTYH-associated polyposis.
Treatment
The therapeutic strategy includes several directions. General treatment includes regular screening and preventive measures. Pharmacological treatment includes the use of chemotherapeutic drugs after surgery. Surgical treatment is the main method and may include segmental resection or total colectomy depending on the extent of the process. Alternative treatments include targeted therapy and immunotherapy in experimental protocols.
List of drugs used to treat this disease
- Fluorouracil (5-FU)
- Oxaliplatin
- Irinotecan
- Cetuximab
- Bevacizumab
- Pemetrexed
Disease monitoring
Regular monitoring includes colonoscopy every 1-2 years starting from the age of 20-25. The prognosis with timely diagnosis and adequate treatment is relatively favorable, but there is a high risk of developing metachronous tumors. The main complications are metastasis, secondary malignancies and the consequences of surgical treatment. According to the Amsterdam II study, five-year survival with early diagnosis is 70-80%.
Age-related features of the disease
At a young age, the disease is characterized by a more aggressive course and rapid progression. In patients over 50 years of age, a less pronounced clinical picture is observed, but the risk of metachronous tumors is higher. A feature of childhood is the prevalence of extraluminal manifestations and difficulties in early diagnosis. In old age, a high frequency of comorbid conditions is noted, which complicates treatment.
Questions and Answers
- How often should a colonoscopy be done for Lynch syndrome? It is recommended to have a colonoscopy every 1-2 years starting from the age of 20-25 years.
- Is it possible to prevent the development of cancer in this syndrome? Although it is impossible to completely prevent its development, regular screening and preventive surgery significantly reduce the risk.
- How does nutrition affect the course of the disease? A diet high in fiber and low in red meat may reduce the risk of developing tumors.
Advice from Dr. Oleg Korzhikov
As an experienced oncogeneticist, I often hear questions about how to live with a diagnosis of Lynch syndrome. The first thing I recommend is not to panic and follow a clear monitoring plan. Many patients wonder whether it is possible to plan a pregnancy - yes, it is possible, but it is important to undergo genetic counseling. The question of the need for prophylactic colectomy often arises - this is an individual decision that is made after a thorough risk analysis. Remember that modern medicine has all the necessary tools for effective disease control.
