Common Psoriasis Vocabulary Explained

Psoriasis is a chronic inflammatory disorder affecting about 2 to 3 percent of adults 20 years old and older. Identifying psoriasis requires looking for characteristic skin changes, including:

  • thickening of skin
  • scaling
  • redness

Here is some of the most pertinent psoriasis vocabulary and symptoms a patient and their loved ones should become familiar with.

Psoriasis Skin Plaques

Dave Bolton/E+/Getty Images

Plaque-type psoriasis, psoriasis vulgaris, is the most common form. The three hallmarks of a plaque of psoriasis are:

  • thickened skin, a plaque, which can vary from barely perceptible to several millimeters thick
  • red skin, which ranges in color from a faint pink to deep red 
  • skin scales, which can range from virtually absent to thick oyster-shell like adherent plates known as ostraceous scales

Auspitz's Sign and Psoriasis

Chris Mansfield/E+/Getty Images

When you scrape or pick off adherent psoriatic scales, pinpoint bleeding known as Auspitz's sign may occur. The pinpoint areas represent the tops of tiny capillaries which undulate vertically throughout the thickened psoriatic skin.

The Koebner Phenomenon

petek arici/E+/Getty Images

The Koebner phenomenon (Koebnerization, isomorphic response) occurs when a new area of psoriasis develops in injured skin. For example, after a surgery, psoriasis may develop around the surgical scar.

This phenomenon may also help explain why psoriasis tends to occur on areas of constant low-intensity trauma such as elbows and knees.

In patients suffering from dandruff or seborrheic dermatitis of the face and scalp, psoriasis can superimpose itself due to irritation and scratching and a crossover or combination dermatitis known as "sebopsoriasis" develops.

Guttate, Pustular and Erythrodermic Psoriasis

Guttate psoriasis diagnosed in a 30 year old female with elevated ASO
Bobjgalindo/Wikimedia Commons

These less common forms of psoriasis differ dramatically from the typical plaque type:

  • In Guttate (drop-like) psoriasis, tiny papules (lesions which can be felt and are less than 1cm in diameter) appear sprinkled throughout the skin.
  • Pustular psoriasis can occur in smaller areas or involve most of the body with innumerable tiny white pustules.
  • Erythrodermic Psoriasis occurs when the entire body turns bright red and scaly. In this instance, you may need a skin biopsy to separate erythrodermic psoriasis from other diseases. 

Typical Locations for Psoriasis

© Dean R. Goodless, M.D.

Plaque-type psoriasis typically involves specific locations on the body including:

  • the scalp
  • elbows and knees
  • genitals
  • belly button
  • buttocks area

In damp areas such as the armpits, under breasts or in the groin, scales become macerated (wet and pasty) and the lesions take on a moist, red and raw appearance closely mimicking a yeast infection in appearance.

On the scalp, a severe form of dandruff-like flaking and scaling can be seen.

Psoriasis of the Hands and Feet

Hands affected by psoriasis on fingers and knuckles. A close view of redness caused by psoriasis on hands resting on a white table. Premium Access XSSML 2125 x 1416 px | 7.08 x 4.72 in @ 300 dpi | 3.0 MP Size Guide Add notes DOWNLOAD AGAIN Details Credit: Alobeti Creative #: 657445350 License type: Royalty-free Collection:
iStock/Getty Images

Psoriasis of the hands and feet can have either a plaque-like appearance or a pustular appearance. In psoriasis patients, pustules form as a part of the inflammatory response.

Very thickened plaques on the palms or soles, being somewhat inflexible, may crack with movement. The resulting fissures can be painful and sometimes become infected.

Severe foot lesions can result in disability by limiting your ability to walk.

Psoriasis In Finger and Toenails

petek arici/E+/Getty Images

Treatment of nail psoriasis can be difficult. Nail changes commonly seen include:

  • thickening
  • lifting
  • pitting of the nails
  • "oil spotting," darkened areas where the nail appears translucent similar to the effect of placing a drop of oil on a sheet of paper, are fairly specific for this disease

Psoriatic Arthritis

Psoriatic arthritis is inflammatory arthritis affecting about 11 percent of patients with moderate to severe psoriasis. 

Was this page helpful?

Article Sources

  • Camisa C. Handbook of Psoriasis, 2nd Ed. Blackwell Publishing, USA (2004)
  • Rachakonda, et al. Journal of the American Academy of Dermatology: Psoriasis prevalence among adults in the United States. (2014)
  • The Cleveland Clinic: Psoriasis