Scientists have found environmental factors and triggers — such as smoking, specific infections, and obesity — are associated with psoriasis. These factors don’t tell the whole story, however: Genetics also play a role.

Psoriasis is an inflammatory skin disease that causes skin cells to grow abnormally fast. Psoriasis is considered an autoimmune disease, and it affects about 2 percent to 3 percent of the world’s population.

Understanding the role of genetics in psoriasis can help someone with the condition learn why it occurs and why certain treatment approaches may work. The genetics of any disease can be very complicated, but as scientists learn more, they may be able to develop better treatment options for prevention and intervention.

Is Psoriasis Hereditary?

Psoriasis seems to run in some families. About 40 percent of people with psoriasis or other psoriatic diseases have a family history of psoriasis or psoriatic arthritis (PsA) in a first-degree relative (parents or siblings).

MyPsoriasisTeam members often discuss the link to psoriatic disease in their families. “My sister and I both have psoriasis, but our parents don’t,” one member wrote. Another said, “I have psoriatic arthritis and so does my daughter.”

Having a family member with psoriasis is a risk factor for developing psoriasis at a younger age, as well as for nail disease and joint inflammation.

Can You Pass Psoriasis Down to Your Children?

According to some research, if both parents have psoriasis, their child has a 65 percent chance of developing the condition. A person’s risk of developing psoriasis is 28 percent if only one parent has the disease.

Studies of identical twins suggest that genes are not the only factor determining whether a person will develop psoriasis. Identical twins share nearly all the same genetic material. Therefore, if the cause of psoriasis was entirely genetic, one twin would have a nearly 100 percent chance of developing it if the other twin had it.

However, this is not the case. Twin studies suggest that if one identical twin has psoriasis, the other twin has a 35 percent to 72 percent chance of developing it. These findings suggest that although certain genes may increase a person’s likelihood of developing psoriasis, genetics aren’t entirely responsible for causing the condition.

A Deeper Look at Genes Associated With Psoriasis

The term “locus” means the location of a gene on a chromosome. “Loci” is the plural form, meaning multiple locations. Scientists have found several loci that contain genes associated with psoriasis. Many different researchers have identified the PSORS1 locus as being associated with psoriasis.

The PSORS1 locus is next to other genes that tell your body how to make proteins known as human leukocyte antigens (HLAs). These proteins typically help the immune system recognize and attack foreign invaders. However, some evidence suggests certain HLA proteins may activate T cells (immune cells) to attack the body’s tissues.

One HLA gene associated with the development of psoriasis is HLA-Cw6. Studies have shown that about 46 percent of people with plaque psoriasis carry the HLA-Cw6 gene, compared to only 7.4 percent of the general population. However, it is possible to have the HLA-Cw6 gene without developing psoriasis. The HLA-Cw6 gene and the PSORS1 locus have also been associated with PsA.

Genome-Wide Association Studies in Psoriasis

A genome-wide association study (GWAS) scans the genetic material of large groups of people to help understand what genetic mutations (changes in the DNA) are associated with particular health conditions.

GWAS researchers have identified several gene changes (called variations) associated with inflammation, the immune system, and the risk of developing psoriasis. The immune system is made up of many complex pathways, like assembly lines in a factory. When you make a change to one part of the assembly line, it can affect the operations of the whole factory. Genes are like blueprints, and when they change, the products in and at the end of the assembly line can change. Cytokines are small proteins that act like products in the immune system assembly line.

Some cytokines and other proteins associated with psoriasis include:

• Interleukin (IL)-12B
• IL-23 receptor
• Nuclear factor-kappa B
• Tumor necrosis factor (TNF)-alpha
• IL-17A

Many of these proteins speed up the growth of skin cells and affect the activity of immune cells. Some of these gene changes are also associated with the development of PsA.

The findings from GWAS about genes and proteins linked to psoriasis can help scientists find new treatments. In fact, they’ve developed several biologic medications to target and block TNF-alpha, IL-17A, or IL-23 for treating psoriasis and PsA.

Does Psoriasis Skip a Generation?

Some members of MyPsoriasisTeam have wondered whether they inherited psoriatic disease from their grandparents. More research is needed to evaluate whether psoriasis or PsA can skip a generation and be passed from grandparent to grandchild. However, one study found that the risk of developing psoriasis if a grandparent had it was about half the rate observed when a parent had psoriasis.

What To Do if You’re Worried Your Child Might Have Psoriasis

If you have psoriasis, you may be worried that your children will also develop the condition. About one-third of people with psoriasis develop the condition before the age of 16 (called early-onset psoriasis). Additionally, early-onset psoriasis seems to be more common in children with a family history of psoriasis.

Be aware of common signs and symptoms of psoriasis in children. Plaque psoriasis is the most common type of psoriasis in children and adults. It can look like silvery or gray scales and purple or red plaques on the elbows, knees, scalp, and back. On darker skin tones, plaque psoriasis could show up as darker or more pigmented patches. The red or purple plaques might not be as noticeable, so it’s important for people with darker skin to recognize the differences in how psoriasis looks.

Guttate psoriasis is another type of psoriasis that affects children and young adults. It can be triggered by a bacterial infection. Lesions will usually look like small, scaling spots on the arms, legs, chest, back, or stomach.

Discuss your concerns with the pediatrician. They can assess whether your child might have psoriasis or refer you to a dermatologist for a diagnosis and treatment recommendations.

The Bottom Line

Scientists have discovered that smoking, certain infections, and obesity can trigger psoriasis, showing a link between environmental factors and the condition. But it’s essential to know that this isn’t the whole picture — genes also play a role. Understanding this mix of environmental factors and genetics is key to understanding more about psoriasis and improving prevention and treatment.

Talk With Others Who Understand

MyPsoriasisTeam is the social network for people with psoriasis and their loved ones. On MyPsoriasisTeam, more than 125,000 members come together to ask questions, give advice, and share their stories with others who understand life with psoriasis.

Is psoriasis hereditary in your family? Share your experience in the comments below, or start a conversation by posting on your Activities page.