Plaque psoriasis is a type of psoriasis that causes thick, raised, scaly patches of skin to develop. Other symptoms include itchiness and inflammation.

Psoriasis is a chronic autoimmune condition that can affect the skin. The scaly patches associated with the condition often form on the elbows, knees, and scalp, and they may last for weeks, months, or years.

It is important that people with psoriasis can identify this condition. Knowing what psoriasis looks like can help people get an accurate diagnosis and prevent them from confusing it with an infection or another severe skin condition.

Plaque psoriasis, which is recognizable due to the scaly plaques it produces on the skin, is the most common type of psoriasis. An estimated 80 to 90 percent of people with psoriasis develop plaques.

Some people will have more than one type of psoriasis. People who have plaque psoriasis may later develop other forms of the condition, such as psoriatic arthritis.

Usually, the turnover of people’s skin cells takes 21 to 28 days. In people with psoriasis, the body attacks healthy skin cells, so new cells develop every 4 to 7 days.

Psoriasis damages patches of skin, leaving areas of redness and irritation. This damage causes the skin to appear scaly and gray and to peel off.

Plaque psoriasis is not an infection, and it is not contagious. However, irritated patches of psoriasis can become infected.

In some people, an infection or injury to the skin can trigger an outbreak of psoriasis. People experiencing their first psoriasis flare-up may mistake their symptoms for an allergic reaction or skin infection.

Doctors typically categorize psoriasis severity according to how much of the body the scaly patches affect.

Some doctors use the Psoriasis Area and Severity Index (PASI) to measure the affected regions of the body and the severity of the symptoms.

Others assess the percentage of the body that the psoriasis plaques affect, assuming that the palm of the hand is equal to one percent of a person’s body surface area (BSA).

Doctors generally classify the severity of psoriasis as follows:

  • Mild psoriasis: Mild psoriasis means that plaques appear on less than 2 percent of the body during a flare.
  • Moderate psoriasis: Moderate psoriasis refers to cases in which plaques cover 3–10 percent of the body.
  • Severe psoriasis: In people with severe psoriasis, plaques cover 10 percent or more of the body.

Severe psoriasis is more likely to have a significant impact on a person’s everyday life.

Research from 2013 found that people with more severe psoriasis were also more likely to have other medical conditions, including lung disease, diabetes, and rheumatic disorders.

A 2016 study identified genetic changes in the skin that related to the severity of psoriasis. The researchers reported that the participants who experienced more severe flare-ups had greater activation of specific genes associated with inflammation.

Plaque psoriasis can occur anywhere on the body, but the most common locations are:

  • the outside of the elbow
  • knees
  • scalp
  • face
  • hands and feet
  • skin folds

Plaque psoriasis may also develop on any area of skin where damage or injury has occurred. For example, it could appear after sunburn, a scrape, infection, or a tattoo.

Although research is promising, doctors cannot yet cure psoriasis. Once a person has had a psoriasis flare, they are likely to have another one.

Patches of psoriasis may clear up after a few months, or they may stay the same, get bigger, or spread across the body. In some people, psoriasis will disappear and not return for years.

Treatment can help reduce the frequency of flares and the severity of symptoms.

People who find that environmental factors trigger their flares can often reduce flare frequency by controlling these triggers, which may include stress or allergies.

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A doctor may prescribe biologics as part of the treatment plan.

Psoriasis has a characteristic appearance that most doctors quickly recognize.

If a doctor suspects psoriasis but is unsure, they may perform a skin biopsy to rule out other causes. The biopsy will involve taking a sample of affected skin and examining it under a microscope.

Treatment depends on the severity of psoriasis. Some people can control their symptoms by avoiding triggers and using over-the-counter (OTC) corticosteroid creams.

People with moderate or severe psoriasis may need medication to control their symptoms. A wide range of medications is available, including:

  • Biologics: These drugs use living cells to target the specific part of the immune system that psoriasis involves. A doctor will usually give the medication by injection in their office.
  • Systemics: These oral or injectable drugs work throughout the body to reduce the severity of autoimmune reactions.
  • New targeted therapies: These drugs also reduce the severity of autoimmune responses but target specific cells. By doing this, they can reduce the risk of side effects.

Other treatment strategies include:

  • lifestyle changes to avoid factors that could trigger a flare
  • prescription-strength steroid creams
  • light or phototherapy, which involves sitting under a sun lamp to speed up healing
  • alternative remedies, including acupuncture, relaxation techniques, and special diets

Many people find that a combination of prescription medications and alternative remedies provides the most relief.

In addition to plaque psoriasis, which is sometimes called psoriasis vulgaris, some other types of psoriasis include:

  • Inverse psoriasis: Inverse psoriasis causes large red patches to form in areas where the skin folds. It tends to affect areas of skin that encounter friction, such as those under the breasts or armpits and along the groin. The lesions are typically flat and shiny.
  • Pustular psoriasis: Pustular psoriasis causes large groups of small, white blisters that may turn red or crack open and bleed. It can affect one or two areas or cover most of the body. Some people also experience nausea, fever, and muscle pain.
  • Palmoplantar psoriasis: Palmoplantar psoriasis affects the soles of the feet and the palms of the hands. The lesions are flat and a pinkish-yellow color.
  • Guttate psoriasis: Guttate psoriasis causes patches of small pink lesions, often on the torso, legs, or arms. It is more common in children than adults.
  • Erythrodermic psoriasis: The rarest and most severe form of psoriasis, erythrodermic psoriasis requires medical treatment. It causes itchy, burning, peeling patches of red skin on much of the body. Some people develop a fever or other symptoms of illness.
  • Psoriatic arthritis: Psoriatic arthritis is a common complication of psoriasis that causes joint pain and inflammation as well as skin symptoms.
  • Nail psoriasis: Nail psoriasis affects the fingernails and toenails, causing them to peel, dent, thicken, or even fall off. People with psoriatic arthritis have a higher likelihood of this condition.

Psoriasis can be frustrating, but it is treatable. People who think that they have psoriasis should see a doctor to discuss treatment options.

Plaque psoriasis is the most common type of psoriasis. It causes patches of thickened skin to develop, often on the arms and around the elbows.

The right treatment can improve a person’s quality of life, reduce the severity of their symptoms, and prevent severe complications, such as psoriatic arthritis.