PsoriasisNet Article
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 this condition.

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:

  • 41% if both parents have

  • 14% if one parent has

  • 6% if one sibling has

  • 2% if neither a parent nor sibling has psoriasis

Other research suggests that the risk may be as high as 50% if both parents have psoriasis.

References:
Nair 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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