Plaque Psoriasis: Hereditary Risk

Margaret Bobonich, DNP, FNP-C, DCNP, FAANP: Melodie, you did some work with the National Psoriasis Foundation really focusing on the genetics of psoriasis.

Melodie Young, MSN, RN, ANP-C: Exactly. Probably in the early 90s, there was a call out by researchers, investigators, and clinicians because we kept seeing large numbers of family members who had psoriasis. We also saw other genetic diseases associated with psoriasis—Crohn disease, where there’s increased likelihood, and rheumatoid arthritis, and ankylosing spondylitis. In the clinical setting, we kept seeing a lot of these similar diseases.

The National Psoriasis Foundation raised the money and we wrote a grant at Baylor University Medical Center in Dallas, [Texas], to try to do research. In 1 year, I spent 26 weekends traveling around the country identifying family members, drawing blood, and getting tissue. Because of that, a pretty significant paper was published in Science that revealed the first gene linkages associated with psoriasis. Since that time, there have been many, many more. We also understand it is a very complex disease.

For clinicians, it’s very important that we let our patients know that it is not their fault when they have psoriasis. They are genetically predisposed. There are things that will trigger it and make it come about, which we’re going to talk about today on this panel, but having the genetic predisposition for your immune system to malfunction and for you to begin to have the development of the disease, whether it’s a few local plaques or whether it is very widespread…

Would anyone like to discuss some of the other genetic factors, as well as the immune system’s role in what we know about it causing the disease or causing the disease to become noted?

Douglas DiRuggiero, PA-C: I just want to drive home the point that there is not yet an isolated gene that says that you have psoriasis. If anything, the research that you did and subsequent research since then has shown us that this is a multifactorial problem. Multiple genes have been identified. It’s a combination of a multigenetic predisposition with a lot of environmental factors. How the numbers play out that I’ve seen is that you have about a 15% to 20% chance of getting psoriasis if you have 1 parent who has psoriasis. If both of your parents have psoriasis, you have a 50% chance of having psoriasis yourself. When we look at the twin data, if 1 twin has it, the other has roughly a 25% of getting it—15% to 25%. That is for nonidentical. If they’re identical, it’s a 75% chance. So those genetics play themselves out.

To me, it’s interesting just to note to our colleagues that this is mostly a disease in folks of western or northern European descent. Caucasians. The closer you get to the equator, the less we see it. Then there are some outlying populations where it’s virtually unheard of—in American Indians, the Inuit population, or the native tribes in that area. Even though it’s far away from the equator, it’s not seen there very often. So there are some interesting caveats of looking at patient populations for which psoriasis is going to be far more prevalent in versus almost never seen. I think there are some important things to note as we step forward.

Melodie Young, MSN, RN, ANP-C: It can present differently in certain populations as well. I think that’s one of the reasons it can become easily missed.

Douglas DiRuggiero, PA-C: We don’t see it much in the Pacific Rim populations—folks from China, from Japan, from Korea. It’s just less. And when it does present, it does present in a very different way from what you may be used to seeing, if you’re used to seeing it in a Caucasian. African Americans, again, can have it, but it is much less prevalent. You have to think of other things, because it could be fooling you. So I think there are important things to note.

Melissa Davis, PA-C: It’s important to jump on what you were saying about the 15% to 20% in 1 parent and 50% with 2. I have a lot of patients who say, “Well, nobody in my family has psoriasis,” so they think they can’t have it. They think that maybe we’re not right, because nobody in their family has psoriasis. So I think it’s important to give them that information—to let them know that, “Just because your mom or dad or grandma or grandpa didn’t have it, that doesn’t mean you’re not going to get it,” if that makes sense.

Margaret Bobonich, DNP, FNP-C, DCNP, FAANP: What’s really interesting is I’ve had patients who’ve come in and they’ve said, “Nobody in my family has it.” We have the discussion. We talk about what psoriasis is. They get the diagnosis. We talk about treatment. They come back for the next office visit and they say, “I had no idea. I told my family about this.”

Melissa Davis, PA-C: Yeah, “My grandma.”

Margaret Bobonich, DNP, FNP-C, DCNP, FAANP: “My grandma.” It’s a very personal thing. Many times it’s in very personal or intimate areas, and people don’t talk about that. So genetics is important, and helping patients understand how to discuss it is important.

Transcript edited for clarity.