Psoriasis is a chronic immune-mediated inflammatory disease (autoimmune disease) that causes the development of scaly red patches on the skin. These patches are raised and can appear anywhere on the body; however, they typically develop on the knees, scalp and the outer side of the elbows. Some of the people who have this disease state that these patches itch, sting, and burn.

Psoriasis is unfortunately linked to other serious health conditions including cardiac disease, diabetes and depression.

How Common is this Condition?

Studies indicate that more than 8 million Americans have this disease; males and females are afflicted with psoriasis equally. Although at least 10 percent of the population inherits genes that could lead to the development of psoriasis, only about 2 to 3 percent of these people actually develop the disease.

Why Do Some People Develop Psoriasis and Not Others? 

It is believed that this relatively low percentage is due to the absence of one of the genes necessary for the disease to develop. In addition, researchers believe that besides the necessary combination of genes, psoriasis development requires that the individual is exposed to a specific external factor as well. This external factor is referred to as a “trigger.”

When Does Psoriasis Develop?

Psoriasis can develop at any age; however, the typical age of onset ranges between 15 and 35. Approximately 15 percent of individuals who develop psoriasis do so before reaching the age of 10. While infants can have psoriasis, onset at this age is extremely rare and can only be verified with close observation. According to the National Psoriasis Foundation, approximately 20,000 children younger than 10 years old are diagnosed with this disease annually.

Disease Severity: Mild, Moderate, or Severe

The treatment options available usually depend on the severity of the disease. Psoriasis is categorized as mild, moderate or severe. Experts determine severity by the percentage of the body that is affected. According to the National Psoriasis Foundation:

  • Mild: affects less than 3 percent of the body
  • Moderate: affects between 3 to 10 percent of the body
  • Severe: affects more than 10 percent of the body

The amount of coverage is not the only factor doctors use to determine the severity of the disease; the effect that psoriasis has on the individual’s quality of life factors in as well.

For example, if the fingers, palm, and thumb are afflicted with psoriasis, 1 percent of the body surface area is affected, which would categorize the disease as mild. However, the impact that the disease has on the individual’s life must also be considered when determining severity here, too. Considering how much people use their hands, this case could be considered more severe.

Almost 60 percent of the individuals diagnosed with this disease report that psoriasis is a substantial problem that negatively affects their daily life. Of those with this disease, approximately 25 percent are diagnosed with the moderate to severe form. Needless to say, these patients experience more of a negative impact on their lives than those who are diagnosed with the milder form of this disease.

What Does Psoriasis Look Like?

Close up of elbows with psoriatic plaques.
Psoriatic plaques. Image courtesy S Bhimji MD. From Psoriasis, StatPearls Publishing LLC. (Creative Commons Attribution 4.0 International License)

The visual characteristics depend on the type of psoriasis an individual has. There are different forms of this condition, including:

  1. Plaque (psoriasis vulgaris, chronic stationary psoriasis, plaque-like psoriasis)
  2. Guttate
  3. Inverse (flexural psoriasis, hidden psoriasis, intertriginous psoriasis)
  4. Localized Pustular
  5. Generalized Pustular
  6. Erythrodermic (psoriatic erythroderma)

Plaque Psoriasis

Man with scaly red and white psoriatic plaques on his elbows.
Fuss Sergey/Shutterstock.com

Eighty to 90 percent of people with psoriasis have this form of the disease.

What Does It Look Like?

Its lesions are red, raised and inflamed. They are covered by thick, scaly, silver “plaques,” which consist of built-up dead skin cells.

Where Does It Form?

These plaques or patches typically develop on the lower back, scalp, elbows, and knees. When nails are affected, they may become pitted or separate from the nail bed.

What Does It Feel Like?

 It is common for these patches to hurt, itch, crack, and bleed.

Guttate Psoriasis

Guttate psoriasis diagnosed in a 30 year old female with elevated ASO, treatment course unspecified.
Image courtesy of Bobjgalindo/Wikipedia (CC BY-SA 4.0)

Approximately 10 percent of the individuals who develop psoriasis have this form of the disease, making it the second most common type.

What Does It Look Like?

Guttate is characterized by small lesions that look like dots. These dots are typically thick or crusty, which makes them appear similar to the patches seen in plaque psoriasis, only much smaller.

When Does It Occur?

The onset of guttate psoriasis frequently occurs during childhood or once an individual becomes a young adult.

What are Some Triggers for this Form of Psoriasis?

A range of health issues can trigger the onset of this form of psoriasis. These conditions include:

  • streptococcal infections,
  • upper respiratory infections,
  • tonsillitis (inflamed tonsils),
  • and skin injury.

Other triggers are stress and certain kinds of medication (beta-blockers, antimalarials, lithium, etc.).

How is It Treated?

Guttate psoriasis can resolve without any treatment whatsoever and never return or it can go into remission and then reappear later.

Inverse Psoriasis

Flexural or inverse psoriasis; shiny red patch covering an armpit
© Professor Raimo Suhonen. Image Courtesy of DermNet New Zealand (CC BY-NC-ND 3.0 NZ)

The lesions with inverse psoriasis develop in the folds of the body; these lesions become irritated from the sweating and the rubbing together of the skin folds, making this form of psoriasis especially difficult to deal with.

What Does It Look Like?

These lesions are extremely red; they may also be shiny and smooth.

Where Does It Occur?

Areas of the body usually affected include:

  • under the arm,
  • behind the knee,
  • under the breasts,
  • around the genitals,
  • in the groin, and
  • the groove of the buttocks.

Who is at Greater Risk?

This form of psoriasis is more common among those with deep skin folds as well as those who are overweight. Many people who have this form of the disease also have another form of psoriasis elsewhere.

Localized Pustular Psoriasis

Psoriasis manum, severe pustular psoriasis
George Henry Fox/Wikipedia

Pustular psoriasis accounts for fewer than 5 percent of psoriasis cases. Adults develop this form more often than children do.

What Does It Look Like?

Pustular psoriasis displays as white blisters that are full of a non-infectious pus. These blisters are referred to as “white pustules,” each surrounded by reddened skin.

Is Pustular Psoriasis Contagious?

The pus is not representative of an infection; this disease is not contagious.

Where Does It Occur?

Pustular psoriasis usually follows a cycle in which the skin reddens and then the pustules and scales develop. Although this form of the disease can develop on any part of the body, the feet and the hands are usually the body parts affected.

Acute Generalized Pustular Psoriasis

Generalized pustular psoriasis; red area covering the lower back of a man
© DermNet New Zealand (CC BY-NC-ND 3.0 NZ)

Acute generalized pustular psoriasis (von Zumbusch pustular psoriasis) is characterized by pus-filled bumps covering most of the body. 

What Does It Look Like?

The first sign is a sudden change in the skin. It will become dry, red, and tender. Hours later, bumps full of pus will develop over most of the body. Within a day, these bumps begin leaking onto the skin. Once the pus dries, the skin also dries and begins to peel. After the peeling process is complete, a smooth, glazed surface of skin lies beneath. Another flare-up can occur within several days or a few weeks.

What Does It Feel Like?

An individual with this form of the disease may experience a headache, a fever, a feeling of unwellness, and muscle weakness.

How Serious is Acute Generalized Pustular Psoriasis?

This form of psoriasis can be fatal; therefore, seeking medical attention at the onset of symptoms is vital.

Erythrodermic Psoriasis

Erythrodermic psoriasis; scaly red patches all over body
© Professor Raimo Suhonen. Image Courtesy of DermNet New Zealand (CC BY-NC-ND 3.0 NZ)

This form of psoriasis is rare, affecting only about 3 percent of those with psoriasis. It usually affects individuals with unstable plaque psoriasis.

What Does It Look Like?

Symptoms include widespread, fiery red skin that covers the majority of the body.

What Does it Feel Like?

Severe pain and itching are other common symptoms of this form of psoriasis. The skin itself can peel off in sheets.

Inflammation around the ankles signals that water is being retained. In addition, the body’s ability to maintain its temperature may be inhibited, which can lead to shivering. Since erythrodermic psoriasis disturbs the chemical balance within the body, it can furthermore cause fluid and protein loss, which could result in the individual becoming extremely ill.

How Serious is Erythrodermic Psoriasis?

This form of psoriasis is linked to congestive heart failure and pneumonia. Therefore, erythrodermic psoriasis can be fatal. Individuals experiencing these symptoms need to seek medical care immediately.

Disclaimer: this article does not constitute or replace medical advice. If you have an emergency or a serious medical question, please contact a medical professional or call 911 immediately. To see our full medical disclaimer, visit our Terms of Use page.


More about Psoriasis