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What Is Plaque Psoriasis?

Medically Reviewed by Debra Jaliman, MD on June 21, 2021

Psoriasis is a skin disease that affects about 8 million Americans. It comes in several forms. Plaque psoriasis is the most common.

Plaques are raised red patches covered with a whitish buildup of dead skins cells called scale. They usually show up on your elbows, knees, scalp, and lower back, but you can have them anywhere. Plaques often itch or hurt.

Causes

plaque psoriasis on elbows

Doctors aren't sure why people get plaque psoriasis. It's considered an autoimmune disease. That means your immune system attacks healthy cells as if it's fighting an infection. This causes new skin cells to grow much faster than normal, and they build up in thick patches.

Whether you get plaque psoriasis depends on your genes and your health history:

  • Heredity. Psoriasis seems to run in families. About one out of three people with psoriasis report having a relative with psoriasis. About 10% of people are born with genes that make them likely to get psoriasis. But only about 3% of people get the disease. Still, If both parents have psoriasis, a child has approximately a 50 percent chance of developing the disease.
  • Triggers. Something has to happen to start your immune system's reaction. Sometimes, it's an injury to your skin or a bad sunburn. It could be a certain medicine, like lithium or malaria drugs. An infection, particularly strep, can bring on psoriasis. So can high levels of stress, Smoking, or drinking alcohol.

Psoriasis isn't contagious. It can't be spread by touch or other close contact.

People with psoriasis tend to have other conditions that cause inflammation, like Crohn's disease, diabetes, metabolic syndrome, fatty liver disease, and obesity. If you have it, you may be more likely to get heart disease, depression, and a kind of eye disease called uveitis. You also have as much as a 1-in-3 chance of getting psoriatic arthritis, which causes joint pain, stiffness, and swelling, and joint deformity.

Diagnosis

A dermatologist (skin doctor) can usually tell if you have plaque psoriasis just by talking with you about your medical history and looking at your skin. But since psoriasis can look like eczema and other skin diseases, diagnosing it can be difficult. In some cases, your doctor may need to do a biopsy. They’ll take a tiny sample of your skin and look at the cells under a microscope.

Types of Plaque Psoriasis

There are a number of different terms that help doctors tell one type of plaque psoriasis from another:

Small plaque psoriasis: This version causes lots of little lesions, each one no bigger than a few centimeters. They may remain separate or they could merge. The crusty parts on top are pink with a finer grain and thinner crust than in large plaque psoriasis. Family history of psoriasis is less common in this version of the condition. 

Small plaque psoriasis can happen at any age, but it’s more common after age 40. It often responds well to phototherapy.

Large plaque psoriasis: Here, the lesions are thicker and often larger with edges that are more clear than in small plaque psoriasis. The crusty parts are red rather than pink and show a whitish-silvery scale.

Large plaque psoriasis can emerge anytime but is more common in those younger than 40. Some studies link the condition to metabolic syndrome. (Metabolic syndrome is when you have some combination of obesity, high cholesterol, high blood sugar, or high blood pressure.) It’s harder to treat than small plaque psoriasis, and it’s more likely to run in families. 

Unstable plaque psoriasis: In unstable psoriasis, the plaques of psoriasis lose their sharp, clear edges as they enlarge and sometimes join together. New plaques may appear too.

Chronic, stable plaque psoriasis: This is the most common form of plaque psoriasis and psoriasis in general. Lesions tend to stick around or reemerge after the first outbreak. The most common areas are the elbows, knees, torso, and head and scalp, though there may be other areas too.

Plaques tend to emerge on both sides of your body. For example, if they show up on one elbow, they will appear on the other one as well. 

Treatment

Psoriasis can't be cured. You'll probably go through cycles where the rash looks better and then flares up again. The goal of treatment is fewer and less severe flare-ups.

You may get medicine to put on your skin or you may take pills, or your doctor may recommend a combination of those. Treatment options include:

  • Topical medications. If you have only a few plaques, your doctor will probably try a prescription cream first. You put these directly on your skin. They help with inflammation or slow the growth of skin cells. Examples include anthralin.,corticosteroids, vitamin A, and vitamin D. You can also try over-the-counter topical medicines. Salicylic acid and coal tar are approved to treat psoriasis. Other ingredients may soothe itch and remove scale, including aloe vera, capsaicin, jojoba,and zinc pyrithione. Topical emollients that you put on after a shower or bath can help keep your skin moist.
  • Light therapy. If the rash is more widespread, your doctor may treat it with ultraviolet light. This is done at their office or with a special box you can keep at home. You may also get relief by going out in the sun, but this can raise your risk of skin cancer. Watch how long you spend outside, and cover up or put sunscreen on places where you don't have plaques.
  • Systemic drugs. If you have a severe case of plaque psoriasis, you may need medicines that work throughout your body. They calm your immune system or make your skin cells grow more slowly. But they can cause serious side effects, like depression, aggressive thoughts, liver problems, or a higher risk of skin cancer. You take systemic drugs like acitretin, cyclosporine, and methotrexate by pill, or your doctor will give you a shot.
  • Biologic drugs. Another kind of systemic drug also targets your immune system. Biologic drugs used to treat psoriasis include adalimumab (Humira), brodalumab (Siliq), etanercept (Enbrel), guselkumab (Tremfya), infliximab (Remicade), ixekizumab (Taltz), risankisumab-rzaa (Skyrizi), secukinumab (Cosentyx), and ustekinumab (Stelara). They're given in a shot or through a vein in your arm. They affect a specific type of immune cell or keep certain proteins from causing inflammation. But these drugs can make it harder for you to fight an infection.

Learn more about advanced treatments for psoriasis.

What You Can Do

Most people who get plaque psoriasis have it for the rest of their lives. You can do a few things to deal with it better:

Avoid triggers. Things like stress and smoking don't cause psoriasis. But they can make it worse. Try to figure out what triggers your flare-ups. You may be affected by:

  • Alcohol
  • Allergies
  • Cold, dry weather
  • Hormones

Watch your diet. There's no proof that specific foods make a difference with psoriasis. But losing weight may keep your symptoms at bay, so it makes sense to eat healthy. And a diet low in fatty meat and dairy products and high in fish and colorful fruits and vegetables may help with inflammation. Read more on psoriasis and your diet.

Take care of your skin. A good moisturizer can keep plaques soft and make you less itchy. Avoid harsh soaps.
A bath with colloidal oatmeal or Epsom salts can also soothe your skin. Try using medicated shampoo for scales on your scalp. Learn about more skin care tips for psoriasis.

Get support. Plaque psoriasis can take an emotional toll. You may feel self-conscious about the way it looks or overwhelmed by what it takes to manage it. Many people with psoriasis become depressed. If you think you need some help, talk with your doctor about therapy or medication. It also helps to talk with people who understand what you're going through and can offer strategies for coping. Find out how to get emotional support during psoriasis treatment.

Work with your doctor. Talk with them about how you're doing and any changes to your condition. You may need to change your treatment over time. Don't suddenly stop using a psoriasis drug, or you could cause a more serious illness. Be aware of symptoms that could signal psoriatic arthritis, like joint pain. Read about what you can do to make your psoriasis treatment work.

Show Sources

American Academy of Dermatology: "Psoriasis."

British Association of Dermatologists: “Psoriasis – An Overview.”

Medscape: "FDA OKs Biologic Guselkumab (Tremfya) for Plaque Psoriasis," "Plaque Psoriasis."

National Institute of Arthritis and Musculoskeletal and Skin Diseases: "Psoriasis."

National Psoriasis Foundation.

UpToDate: "Treatment of psoriasis."

Weigle, N., American Family Physician, May 2013.

Bruce E. Strober, MD, PhD, associate director of dermatopharmacology, Department of Dermatology, New York University School of Medicine; co-director of the Psoriasis and Psoriatic Arthritis Center; consultant for Amgen, Biogen, Genentech, Fujisawa, and 3-M.

Jeffrey M. Weinberg, MD, director of the Clinical Research Center, St. Luke's-Roosevelt Hospital Center, New York City; assistant clinical professor of dermatology, Columbia University College of Physicians and Surgeons; consultant for Amgen and Genentech.

Abel, E. "Dermatology III: Psoriasis," ACP Medicine, April, 2005.

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