Psoriasis is a chronic disease that causes scaling and inflammation of the skin. This occurs when skin cells quickly rise from below the surface of the skin and pile up before they have a chance to mature. Normally, this process takes about a month, but in psoriasis it may occur in a few days. This often results in patches of thick, red and inflamed skin covered with silvery scales. These patches are referred to as plaques and usually itch or feel sore. They can occur on the elbows, knees, parts of the legs, scalp, lower back, face, palms and soles of the feet; however, plaques can develop on the skin anywhere on the body. The disease can also affect the fingernails, toenails, soft tissues of the genitals and the inside of the mouth.

Psoriasis can occur in all age groups, but it primarily develops in adults. Males and females are affected equally by this disease. It affects greater than 3 percent of the U.S. population, which is more than five million adults.

About 30 percent of people with psoriasis experience cracks in the skin around affected joints. This results in joint inflammation that can produce symptoms of arthritis. This condition is called psoriatic arthritis. Another type of psoriasis is called plaque psoriasis and occurs when skin lesions are red at the base and are covered by silvery scales.


Psoriasis is a skin disorder related to a person’s immune system. A specific type of white blood cell, called a T cell, normally helps to protect the body against infection. A person with psoriasis has overactive T cells that trigger immune responses that lead to inflammation and rapid turnover of skin cells. Many individuals with psoriasis have a family history of this disease. Researchers believe that genes for psoriasis are being passed from parent to child.

In addition, a person with psoriasis may have certain times when their skin worsens. This is called having a flare. Certain conditions that may cause flares are infection, stress and changes in climate that can dry the skin.


There are different types of psoriasis and people often present with certain symptoms listed below:

Plaque psoriasis
Skin lesions are red at the base and covered by silvery scales.
Guttate psoriasis
Small drop-shaped lesions can appear on the trunk, limbs and scalp; this type of psoriasis is often triggered by upper respiratory infections.
Pustular psoriasis
Blister of noninfectious pus appear on the skin; this type of psoriasis may be caused by medications, infections, stress or exposure to certain chemicals.
Inverse psoriasis
Smooth, red patches occur in the folds of the skin near the genitals, under the breasts, or in the armpits; symptoms can become worse if there is a friction or if a person sweats.
Erythrodermic psoriasis
Widespread reddening and scaling appears on the skin; this is often caused by severe sunburn or by taking certain medications.
Psoriatic arthritis
Cracks in the skin occur around joints due to psoriasis; this leads to inflammation in the joints which produces symptoms of arthritis.


Psoriasis often looks similar to other skin diseases. Therefore, doctors can have a difficult time diagnosing the disease. Doctors will diagnose a person with psoriasis based on their physical exam and may also need to take a small skin sample and examine it under a microscope.


Specialty drug list

Doctors treat psoriasis based on a “1-2-3” approach. Treatment depends on the severity of the disease, the size of the areas that are affected, the type of psoriasis and the person’s response to previous treatments. In step 1, medicine is applied to the skin (topical treatment). Step 2 uses light treatments (phototherapy). Finally, step 3 involves a person taking medicines either by mouth or by injection. These medicines treat the whole immune system (systemic therapy).

Step 1: Topical treatment
This type of treatment is applied directly to the skin and can be soothing to the patient. Many patients respond well to ointment or cream forms of corticosteroids, vitamin D3, retinoids, coal tar or anthralin.
Step 2: Phototherapy
A doctor will treat a patient with artificial ultraviolet light, administered in their office. This helps to decrease inflammation and slow the turnover of skin cells that cause scaling.
Step 3: Systemic therapy
Doctors may prescribe medicines that are taken by mouth or injected for patients that have more severe forms of psoriasis. Examples of these types of medicines are biologic response modifiers that help to suppress the immune system.

Side Effects

There are different side effects that can occur depending on the type of treatment a person receives:

Topical treatments:

Thinning of the skin may develop after long-term use.
Vitamin D3
Irritation of the skin may occur but can be reduced if used with a corticosteroid.
Irritation of the skin may occur but can be reduced if used with a corticosteroid.
Coal tar
High-strength forms can irritate the skin, have a strong odor and may stain the skin or clothing.
Stains the skin, bathtub and sink, and can turn clothing brown or purple.


Ultraviolet B (UVB) phototherapy
UVB must be given in the doctor’s office because too much light can cause skin damage and increase the risk of skin cancer.

Systemic therapy:

Treatment may cause liver damage and decrease red and white blood cells and platelets.
Biologic response modifiers
Treatment may increase risk of infection.


There are many resources and organizations available to help, providing support, advocacy and information:

American Academy of Dermatology

National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)

National Psoriasis Foundation


National Institutes of Health. NIAMS. Accessed November 30, 2011.