Psoriasis is a skin condition characterized by itchy scales, inflammation, and redness. It usually occurs on the scalp, knees, elbows, hands, and feet.
About 7.5 million people in the United States have psoriasis.
Psoriasis is an autoimmune disease. Immune cells in your blood mistakenly recognize newly produced skin cells as foreign invaders and attack them. This can cause the overproduction of new skin cells beneath the surface of your skin. These new cells migrate to the surface and force out existing skin cells. That causes the scales, itching, and inflammation of psoriasis.
Genetics almost certainly plays a role. Research has shown that susceptibility to psoriasis is inherited. Read on to learn more about the role of genetics in the development of psoriasis.
Psoriasis usually appears between the ages of 15 and 35. It may occur at any age, however. For example, about 20,000 children under the age of 10 are diagnosed with psoriasis every year.
Psoriasis can occur in people with no family history of the disease. Having a family member with the disease increases your risk.
- If one of your parents has psoriasis, you have about a 10 percent chance of getting it.
- If both of your parents have psoriasis, your risk is 50 percent.
- If you have a sibling with psoriasis, you are four to six times more likely to develop psoriasis compared with the general population.
Scientists working on the genetic causes of psoriasis start by assuming that the condition results from a malfunction of the immune system. Research on psoriatic skin shows that it contains large numbers of immune cells that produce inflammatory molecules known as cytokines.
Psoriatic skin also contains gene mutations known as alleles. Early research work in the 1980s led to the belief that one specific allele might be responsible for passing on the disease through families. Researchers later discovered that the presence of this allele, HLA-Cw6, wasn’t sufficient to cause a person to develop the disease.
Use of more advanced techniques has led to the identification of about 25 different regions in human genetic material (the genome) that may be associated with psoriasis. As a result, genetic studies can now give us an indication of a person’s risk of contracting psoriasis. The link between the genes that are associated with psoriasis and the condition itself isn’t yet fully understood.
Psoriasis involves an interaction between your immune system and your skin. That means it’s hard to know which is the cause and which the effect. The many new findings in genetic research have provided important insights, but we still don’t clearly understand what causes a psoriasis outbreak. The precise mechanism by which psoriasis is passed from parent to child is also not fully understood.
Most people with psoriasis have periodic outbreaks or flare-ups followed by periods of remission. About 40 percent of people with psoriasis also experience inflammation of the joints that resembles arthritis. This is called psoriatic arthritis.
Environmental factors that may trigger a psoriasis onset or flare-up include:
- cold and dry weather
- HIV infection
- drugs such as lithium, beta-blockers, and antimalarials
- withdrawal of corticosteroids
Injury or trauma to a portion of skin may sometimes become the site of a psoriasis flare-up. Infection may also be a trigger. The National Psoriasis Foundation notes that infection, and particularly strep throat in young people, is reported as a trigger for psoriasis onset.
Some diseases are more likely in people with psoriasis than in the general population. The incidence of Crohn’s disease, ulcerative colitis, and some other types of inflammatory bowel disease can be about four to seven times greater among people with psoriasis than those without.
People with psoriasis have an increased incidence of:
- heart disease
- type 2 diabetes
- metabolic syndrome
- depression and suicide
- alcohol consumption
Gene therapy isn’t currently available as a treatment, but there’s an expansion of research into the genetic causes of psoriasis. In one of the many promising discoveries, Researchers found a rare gene mutation that’s linked to psoriasis.
The gene mutation is known as CARD14. When exposed to an environmental trigger, such as an infection, this mutation produces plaque psoriasis. Plaque psoriasis is the most common form of the disease. It accounts for about 80 percent of all cases. This discovery helped establish the connection of the CARD14 mutation to psoriasis.
These same researchers also found the CARD14 mutation present in two large families that had many family members with plaque psoriasis and psoriatic arthritis.
This is one of a number of recent discoveries that hold promise that some form of gene therapy may one day be able to help people living with psoriasis or psoriatic arthritis.
For mild to moderate cases, dermatologists usually recommend topical treatments such as creams or ointments. These can include:
- coal tar
- salicylic acid
- vitamin D
If you have a more severe case of psoriasis, your doctor may prescribe phototherapy and more advanced systemic medications, taken orally or by injection.
Researchers have established a link between psoriasis and genetics. Having a family history of the condition also increases your risk. More research is needed to fully understand the inheritance of psoriasis.