What causes plaque psoriasis?

An exact cause for plaque psoriasis is not known, but it seems to be an inherited immune disorder in which the immune system speeds up the normal skin cell production cycle. In normal skin, new skin cells form deep inside the layers of skin. Over time, about a month, they rise to the surface and ultimately fall off when other cells rise. With plaque psoriasis, this process happens too rapidly. Skin cells rise to the surface in a matter of days. Instead of falling off, they pile up into plaques - dry, raised lesions - on the skin.

You get to go to Sweden and collect your Nobel if you can determine without a doubt the answer to this one. The exact cause of plaque psoriasis is still stumping experts, but they have some clues. Since it’s an autoimmune disease, it may be caused by genetics, the environment, or more likely the combination of both. Experts believe that something (skin injury, stress, medication) mistakenly triggers your immune system and results in skin-cell growth being shifted into sixth gear, like a car in the Daytona 500. It produces skin more quickly, and that causes the scales of more rapid dead skin, so it keeps building and building up which is seen as the plaques or raised red/white areas.

No one knows exactly what causes psoriasis. However, it is known that the immune system and genetics play major roles in its development. Most researchers agree that the immune system is somehow mistakenly triggered, which causes a series of events, including acceleration of skin cell growth. A normal skin cell matures and falls off the body in 28 to 30 days. A skin cell in a patient with psoriasis takes only 3 to 4 days to mature and instead of falling off (shedding), the cells pile up on the surface of the skin, forming psoriasis lesions.

Scientists believe that at least 10 percent of the general population inherits one or more of the genes that create a predisposition to psoriasis. However, only 2 to 3 percent of the population develop the disease. Researchers believe that for a person to develop psoriasis, the individual must have a combination of the genes that cause psoriasis and be exposed to specific external factors known as “triggers.”

Triggers include stress, skin injuries, and medications, including lithium, which is used to treat manic depression and other psychiatric disorders. Lithium aggravates psoriasis in about half of those with psoriasis who take it. Other medications that trigger plaque psoriasis include antimalarials (Plaquenil, Quinacrine, chloroquine and hydroxychloroquine), Inderal, Quinidine and Indomethacin.

At this time, it is not known what causes plaque psoriasis. What experts do know is there's a link between the immune system, genetics and plaque psoriasis. The majority of researchers conclude that with plaque psoriasis, the immune system is triggered in error. This results in many events, including the speeding up of skin cell growth. Here's the difference between a normal skin cell and a skin cell in someone with plaque psoriasis:

• It takes 28 to 30 days for a normal skin cell to fully mature and fall off of the body.
• It takes only 3 to 4 days for a  skin cell to full mature in someone with plaque psoriasis.
• With plaque psoriasis, the cells do not fall off the skin. They keep building on the skin's surface to form the raised surfaces of psoriasis or psoriasis lesions.

For a person to develop plaque psoriasis, scientists believe there must be a combination of genetics and exposure to the environmental trigger.