Cowden syndrome is a genetic syndrome usually caused by mutations in a gene known as PTEN. Mutations in this gene have been found in about 40-80 percent of people with a clinical diagnosis of CS and about half of all people with a clinical diagnosis of Bannayan-Ruvalcaba-Riley syndrome. The fact that both conditions are caused by mutations in the same gene explains why they share many similarities and why a physician must consider both possibilities when deciding upon a diagnosis and your health care management plan.
Genes serve as the basic unit of heredity, providing the body’s instructions for growth and development. Every cell of the human body has a complete set of this genetic information. Genes are composed of DNA and are housed on structures called chromosomes. There are 23 pairs of chromosomes (46 total). A child receives one chromosome of each pair from his or her mother's egg and one from their father's sperm. In this way, a child inherits half the information needed for development (including one copy of the PTEN gene) from each parent. Tests can be done to look for mutations in genes that can lead to disease.
The PTEN gene functions as a tumor suppressor. Tumor suppressor genes normally ensure that cells do not grow or divide more than they are supposed to. Only one copy of a tumor suppressor gene is needed to control cell growth. This means that when a person has inherited one PTEN gene with a mutation, the other, functional copy is still able to successfully control cell growth. However, if anything damages the second, functional copy of the PTEN gene in any cell, that person can develop either a benign and cancerous growth. Thus, although a person with CS inherits an increased risk for tumor development, they do not inherit the tumor or cancer itself.