Cowden Syndrome
A Guide for patients and their families
What Causes Cowden Syndrome?
Sarah Burton, UI Health Care
Joy Larsen Haidle, MS, CGC, UI Health Care
Heather Hampel, MS, CGC, Ohio State University
Charis Eng, MD, PhD, Ohio State University
Peer Review Status: Internally reviewed by the
authors
First Published:
Last Revised: April 2002
Cowden syndrome is a genetic syndrome often
caused by a change in a tumor suppressor gene known as PTEN. Changes
in this gene have been identified as the cause of most CS and a
proportion (perhaps half) of Bannayan-Riley-Ruvalcaba syndrome. The
fact that both conditions are caused by changes 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.Every cell of the human body has a complete
copy of our genetic information. Genes serve as the basic unit of
heredity, providing the instructions for growth and development.
Genes are composed of DNA and are housed on structures called
chromosomes. There are 23 pairs of chromosomes (46 total
chromosomes). The first 22 chromosome pairs hold the instructions for
your body to grow, develop; and function properly. The last pair
determines if you are male or female: males usually have one X and
one Y chromosome while females usually have two X
chromosomes.Chromosomes are passed from parent to child. 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 from each parent. A
picture of all the chromosome pairs lined up together is called a
karyotype (Diagram 2). Examination of the chromosomes provides valuable
information because experts can see if there may be a structural
change that may cause a genetic condition.
Diagram 2. Normal male karyotype
Looking at karyotypes is not the only way to
look for a genetic problem. The genes within each chromosome can have
changes as well. These changes are too small to see under a
microscope, so scientists have developed other tests to look for
small changes in the sequence (pattern) of a gene. A change in the
sequence of the PTEN gene causes Cowden syndrome and a proportion of
Bannayan-Riley-Ruvalcaba syndrome.The PTEN gene is located on chromosome 10
(above) and functions as a tumor suppressor. Tumor suppressor genes
keep cell growth in balance; ensuring the cells do not grow (divide)
more than they are supposed to. Only one copy of a gene is needed to
control cell growth. While one gene may be changed, the functional
copy is still able to successfully control cell growth. When an
individual has CS, they have an inherited change in one of their PTEN
genes. Random events* that occur throughout life may cause a change
in the second copy of their PTEN gene, which may make the gene not
work properly. Cells with two non-working copies of the PTEN tumor
suppressor gene are at increased risk for benign and malignant cell
growth. Remember, a person with CS inherits a predisposition or an
increased chance (risk) for tumor growth; they do not inherit cancer
itself.
* Random events that can change our DNA are
uncontrollable. Incidents causing small changes at the cellular level
can occur during normal cell growth or can be caused
by environmental factors such as radiation. Everyone experiences several DNA changes throughout his or her lifetime, but most are not significant enough to be noticed.
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