Do you know someone who has psoriasis? This common skin disease affects about 7.5 million people in the U.S.

Psoriasis histology image
(Above) The skin's layers in normal skin (at left) versus in psoriasis (at right). These images show epidermal cells (pink upper layer) growing at an abnormally rapid rate in psoriasis.

Psoriasis is an autoimmune disorder

Psoriasis is an autoimmune disorder that causes skin cells to divide and grow much faster than normal, resulting in raised, red scaly patches of skin that itch or burn. Many people with psoriasis also develop symptoms affecting their nails, such as pitting, discoloration or nail separation. Although psoriasis affects people of all ages, psoriasis symptoms often first appear between the ages of 15 and 301.

Psoriasis is treatable but not curable

There is currently no cure for psoriasis. Flare ups of symptoms may come and go throughout life, and can be triggered by stress, skin injury, too much sun, and many other things. Fortunately, symptoms can be effectively treated, often providing periods during which skin is clear.

You cannot "catch" psoriasis

Psoriasis is not contagious, meaning it cannot be spread from one person to another. In general, about two to three percent of people have psoriasis. Your risk for having psoriasis results from the versions of genes you inherit from your parents. If one or both of your parents has psoriasis, your chance of developing psoriasis is increased. About 30 percent2 of those with psoriasis also develop psoriatic arthritis, a form of inflammatory arthritis.

Genetics are at the heart of it all

Michigan Medicine’s Dr. James T. Elder explains, “While genetic differences are at the heart of it all, the genetics of psoriasis (and many other “complex” genetic diseases) is quite different from that of “single-gene” diseases. In single-gene diseases, something is very “wrong” with one particular gene, which by itself is enough to cause the disease. In psoriasis, much smaller differences in a much larger number of genes (63 so far)3 “add up”, to an increased risk for getting psoriasis, especially under certain environmental conditions.

Because the immune system is very important in psoriasis and many other autoimmune diseases, many of the key environmental signals likely involve the immune system (in psoriasis, strep throat is a prime example). This combination of multiple genetic factors, with the environment as the “wild card”, is why it is hard to make a one-to-one connection between one particular gene and who gets psoriasis. Still, the genetic research has created a “Rosetta stone” that is already helping scientists to understand psoriasis and many other diseases.”

Psoriasis image

(Above) In psoriasis, red inflammed skin is often topped with silvery scales of dead skin. Shown: elbow skin.

1. American Academy of Dermatology. “Psoriasis.” Available from: Accessed August 3, 2017.
2. National Psoriasis Foundation. “About Psoriatic Arthritis.” Available from: Accessed August 3, 2017.
3. Michigan Medicine - University of Michigan. "Largest psoriasis meta-analysis to date yields new genetic clues." Available from: Accessed August 3, 2017.


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