Genes and Psoriasis: Answers to Your Questions
How did I get psoriasis if no
one in my family has it?
Research suggests that about 10% of us inherit genes that make it
possible to develop psoriasis, but only 2% or 3% actually develop
For psoriasis to appear, it seems that a series of events must
occur. First, the person must inherit the “right” mix of genes that
can cause psoriasis. While others in your family may carry some of
the genes, they may not have had the “right” mix.
It also is possible that some relatives had the “right” mix of genes
but did not get psoriasis because they were not exposed to the
“right” trigger. For psoriasis to develop, the person must be
exposed to a trigger that will turn on the genes that cause
psoriasis. It appears that different genes respond to different
triggers, so what triggers psoriasis in one person may not trigger
psoriasis in another person. Common triggers for psoriasis include
getting strep throat, experiencing an extremely stressful event, and
taking certain medications. Some medications such as lithium, an
anti-malarial, and some beta-blockers (medication used to treat high
blood pressure) can trigger psoriasis.
Lifestyle also may play a role. Smoking, a sedentary lifestyle, and
heavy alcohol consumption are believed to increase the risk of
developing psoriasis in people who are genetically susceptible.
If someone in my family has psoriasis, should everyone in the
family get genetic testing?
If your family wants to know who will develop psoriasis and who will
not, genetic testing cannot provide that information. To date, there
is no way to predict who will get psoriasis. The genetic testing
available today is limited to identifying some of the variations in
DNA that make a person susceptible to developing psoriasis. This is
why the commercially available genetic test for psoriasis is offered
“for informational purposes only.” It can tell you if you have some
of the genes associated with psoriasis, but that is all.
What is the lifetime risk for developing psoriasis when one
parent has psoriasis?
One study that looked at how people inherit psoriasis suggests that
the risk for developing psoriasis is a follows:
Other research suggests that the
risk may be as high as 50% if both parents have psoriasis.
RP, Stuart PE, Nistor I et al. “Sequence and haplotype
analysis supports HLA-C as the psoriasis susceptibility 1 gene.”
Am J Hum Genet 2006; 78: 827-51.
Gudjonsson JE and Elder JT. “Psoriasis.” In: Wolff, K, Goldsmith LA,
Katz SI, et al. (editors) Fitzpatrick’s Dermatology in General
Medicine. 7th ed. New York: McGraw Hill Medical;
2008. p. 169-93.
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