The human body is an intricate network, and genes serve as fundamental blueprints guiding its development and function. The STK11 gene plays a significant role in maintaining cellular health. Understanding gene function and the consequences of its alterations offers insight into various health conditions.
The STK11 Gene’s Normal Function
The STK11 gene, also identified as LKB1, provides instructions for creating the enzyme serine/threonine kinase 11. This enzyme acts as a tumor suppressor, regulating cell growth and division. It prevents uncontrolled cell multiplication that could lead to abnormal growths.
The enzyme also contributes to cell polarization within tissues. It helps determine cellular energy use and promotes programmed cell death (apoptosis), which removes damaged or unnecessary cells. It is also involved in normal development before birth.
Understanding Peutz-Jeghers Syndrome
Mutations in the STK11 gene cause Peutz-Jeghers Syndrome (PJS), a rare inherited disorder. PJS is characterized by hamartomatous polyps, noncancerous growths primarily in the gastrointestinal tract. These polyps are most common in the small intestine but can also appear in the stomach and colon.
The syndrome also presents with unique pigmented spots (mucocutaneous lesions) on the skin and mucous membranes. While polyps are benign, they can cause complications like bleeding, intestinal obstruction, or intussusception. Individuals with PJS also face an increased lifetime risk of developing various cancers.
Identifying Peutz-Jeghers Syndrome
Diagnosis of PJS often begins with recognizing clinical signs and symptoms, which appear during childhood. These include characteristic dark brown or blue-gray pigmented spots around the mouth, nose, eyes, on the fingers, and inside the mouth. These spots usually appear by age 5 but may fade during puberty and adulthood.
Symptoms related to polyps, such as abdominal pain, nausea, vomiting, and rectal bleeding, often emerge between 10 and 30 years of age. Imaging techniques like endoscopy, colonoscopy, or capsule endoscopy, which uses a tiny camera to take pictures inside the digestive system, detect polyps. A definitive diagnosis is confirmed through genetic testing for the STK11 gene mutation.
Living with Peutz-Jeghers Syndrome
Managing Peutz-Jeghers Syndrome involves proactive surveillance and ongoing medical care. Regular endoscopic surveillance, including gastroscopy and colonoscopy, is recommended to detect and remove polyps. Screenings are often advised starting around age 8, with subsequent checks every 1 to 3 years if polyps are found.
Individuals with PJS have an increased risk for various cancers, including those of the gastrointestinal tract, breast, pancreas, lung, ovary, and testicles. Screening for these cancers is a standard part of management, often starting at younger ages than in the general population, such as annual mammograms for women and pancreatic cancer screening. A multidisciplinary medical team coordinates this comprehensive care, which may also include yearly testicular exams for men.
Inheriting Peutz-Jeghers Syndrome
Peutz-Jeghers Syndrome is typically inherited in an autosomal dominant pattern. This means one copy of the altered STK11 gene in each cell is sufficient to increase the risk of developing polyps and tumors. If an individual has PJS, each child has a 50% chance of inheriting the mutated gene.
While many individuals with PJS have an affected parent, approximately 25-50% of cases result from a new (de novo) mutation in the STK11 gene, meaning the mutation was not inherited from either parent. Genetic counseling is an important resource for affected families. It helps individuals understand inheritance risks, discuss testing options, and explore family planning considerations.