Which are the causes of Peutz-Jeghers syndrome?

TL;DR: Peutz-Jeghers syndrome is a rare genetic disorder primarily caused by a mutation in the STK11 (also known as LKB1) gene, which provides instructions for making a protein that acts as a tumor suppressor. This inherited condition follows an autosomal dominant pattern, meaning a single copy of the altered gene from one parent is sufficient to cause the syndrome, though approximately 25% of cases arise from new, sporadic mutations in individuals with no family history.

What is the genetic cause of Peutz-Jeghers syndrome?

The primary cause of Peutz-Jeghers syndrome is a pathogenic variant (mutation) in the STK11 gene located on chromosome 19p13.3. Think of the STK11 gene as a "master switch" that regulates cell growth and division; when this gene functions correctly, it produces a protein that prevents cells from growing or dividing too rapidly. In individuals with Peutz-Jeghers syndrome, this gene is mutated, causing the protein to malfunction or be absent. Without this crucial tumor-suppressor mechanism, cells in the gastrointestinal tract and other tissues can grow uncontrollably, leading to the development of characteristic benign polyps known as hamartomas.

Is Peutz-Jeghers syndrome always inherited from parents?

While Peutz-Jeghers syndrome is often described as an inherited condition, it is not always passed down through generations. It follows an autosomal dominant inheritance pattern, meaning if one parent has the mutation, each child has a 50% chance of inheriting it. However, clinical data indicates that about 25% of cases occur in people with no family history of the disorder. These are known as de novo or sporadic mutations, which occur spontaneously in the egg or sperm cell at the time of conception or during early embryonic development. Currently, there are no known environmental triggers, such as diet or lifestyle choices, that cause the initial onset of Peutz-Jeghers syndrome.

How does the mutation lead to disease symptoms?

The absence of functional STK11 protein leads to a cascade of cellular issues. The following factors contribute to the clinical presentation of Peutz-Jeghers syndrome:

• Hamartomatous Polyps: The primary clinical feature, usually appearing in the small intestine, stomach, and colon during childhood or adolescence.


• Cellular Signaling Disruption: The loss of the STK11 gene disrupts the mTOR signaling pathway, which is a key regulator of metabolism and cell growth.


• Increased Cancer Risk: Because the body loses a critical "brake" on cell division, individuals with Peutz-Jeghers syndrome have an increased lifetime risk of developing various cancers, including gastrointestinal, breast, and reproductive tract cancers.

Is the cause of Peutz-Jeghers syndrome fully understood?

While we have a clear understanding of the STK11 gene's role, research into Peutz-Jeghers syndrome continues. Scientists are currently investigating why some people with the same mutation exhibit more severe symptoms than others, a concept known as variable expressivity. Furthermore, in approximately 10% to 20% of patients who meet the clinical criteria for Peutz-Jeghers syndrome, a mutation in the STK11 gene cannot be identified using standard testing. This suggests that there may be other, as-yet-undiscovered genetic modifiers or rare mutations in other genes that contribute to the development of the condition.

Next steps

• Consult a clinical geneticist to discuss genetic testing options for you and your family members.


• Speak with a gastroenterologist regarding a routine surveillance program, as early detection of polyps is essential for managing the condition.


• Connect with the 167 community members on DiseaseMaps.org who are living with this condition to share experiences and coping strategies.


• Maintain a detailed family medical history to assist your medical team in assessing cancer risk.

Medical disclaimer: This information is for educational purposes only and does not constitute medical advice; please consult a qualified healthcare provider for diagnosis and treatment.

References

• NIH Genetic and Rare Diseases (GARD) Information Center: Peutz-Jeghers Syndrome.


• OMIM (Online Mendelian Inheritance in Man): Entry #175200 (Peutz-Jeghers Syndrome).


• Orphanet: Rare Disease Database (ORPHA:713).


• PubMed/NCBI: Clinical reviews on STK11-related tumor suppression pathways.