Scientists believe that at least 10 percent of people inherit one or more of the genes that could eventually lead to psoriasis. However, only 2 percent to 3 percent of the population develops the disease. Researchers believe that for a person to develop psoriasis, that person must have a combination of the genes that cause psoriasis and be exposed to specific external factors known as “triggers.”
How do genes work?
Genes control everything about a person, from height to eye color. When genes are working normally, the body and its cells function normally. When a misstep occurs in the way a gene works, a genetic disease such as psoriasis may result.
Which genes make a person more likely to develop psoriasis?
Research into the genetics of psoriasis didn’t begin until the early 1970s. Recently, it has exploded in scope, thanks to improvements in medical and genetic technology, and increased funding.
In 2006, the Foundation began collecting DNA samples for the National Psoriasis Victor Henschel BioBank. The BioBank is slated to be the world’s largest collection of psoriasis-related DNA in the world available to qualified researchers. The first BioBank DNA samples were released to researchers in 2010.
Scientists have now identified about 25 genetic variants that make a person more likely to develop psoriatic disease. At the University of Michigan, Dr. J.T. Elder and his team of researchers have identified several areas on the human genome where more than one gene may be involved in psoriasis and psoriatic arthritis.
At the University of California-San Francisco, Dr. Wilson Liao is using new genetic sequencing technology to find rare "trigger genes" that may be the leading causes of psoriasis in certain individuals.
Working with DNA samples from a large family that includes many people with psoriasis, Anne Bowcock, Ph.D., a professor of genetics at Washington University School of Medicine in St. Louis, has identified a gene mutation known as CARD14 that when triggered leads to plaque psoriasis.
At the University of Utah, Drs. Gerald Krueger and Kristina Callis Duffin have carefully catalogued the psoriasis of more than 1,200 patients. By comparing the genes of each individual to the way psoriasis shows up on his or her body, the team hopes to understand which genes are involved in specific types of disease.
Using a NPF Discovery grant, British researcher Francesca Capon found that a mutation to the gene called IL36RN might be involved in the three forms of pustular psoriasis.
What triggers psoriasis?
Psoriasis triggers are not universal. What may cause one person's psoriasis to become active, may not affect another. Established psoriasis triggers include:
Stress can cause psoriasis to flare for the first time or aggravate existing psoriasis. Relaxation and stress reduction may help prevent stress from impacting psoriasis.
Injury to skin
Psoriasis can appear in areas of the skin that have been injured or traumatized. This is called the Koebner [KEB-ner] phenomenon. Vaccinations, sunburns and scratches can all trigger a Koebner response. The Koebner phenomenon can be treated if it is caught early enough.
Certain medications are associated with triggering psoriasis, including:
- Lithium: Used to treat manic depression and other psychiatric disorders. Lithium aggravates psoriasis in about half of those with psoriasis who take it.
- Antimalarials: Plaquenil, Quinacrine, chloroquine and hydroxychloroquine may cause a flare of psoriasis, usually two to three weeks after the drug is taken. Hydroxychloroquine is the least likely to cause side effects.
- Inderal: This high blood pressure medication worsens psoriasis in about 25 percent to 30 percent of patients with psoriasis who take it. It is not known if all high blood pressure (beta blocker) medications worsen psoriasis, but they may have that potential.
- Quinidine: This heart medication has been reported to worsen some cases of psoriasis.
- Indomethacin: This is a nonsteroidal anti-inflammatory drug used to treat arthritis. It has worsened some cases of psoriasis. Other anti-inflammatories usually can be substituted. Indomethacin's negative effects are usually minimal when it is taken properly. Its side effects are usually outweighed by its benefits in psoriatic arthritis.
Anything that can affect the immune system can affect psoriasis. In particular, streptococcus infection (strep throat) is associated with guttate psoriasis. Strep throat often is triggers the first onset of guttate psoriasis in children. You may experience a flare-up following an earache, bronchitis, tonsillitis or a respiratory infection, too.
It's not unusual for someone to have an active psoriasis flare with no strep throat symptoms. Talk with your doctor about getting a strep throat test if your psoriasis flares.
Other possible triggers
Although scientifically unproven, some people with psoriasis suspect that allergies, diet and weather trigger their psoriasis.