What Is Psoriasis?

Psoriasis is a chronic (long-lasting) skin disease of scaling and inflammation that affects greater than 3.1 percent of the U.S. population, or more than 6.7 million adults. Although the disease occurs in all age groups, it primarily affects adults. It appears about equally in males and females.

Psoriasis occurs when skin cells quickly rise from their origin below the surface of the skin and pile up on the surface before they have a chance to mature. Usually this movement (also called turnover) takes about a month, but in psoriasis it may occur in only a few days.

In its typical form, psoriasis results in patches of thick, red (inflamed) skin covered with silvery scales. These patches, which are sometimes referred to as plaques, usually itch or feel sore. They most often occur on the elbows, knees, other parts of the legs, scalp, lower back, face, palms, and soles of the feet, but they can occur on skin anywhere on the body. The disease may also affect the fingernails, the toenails, and the soft tissues of the genitals, and inside the mouth.

How Does Psoriasis Affect Quality of Life?

Individuals with psoriasis may experience significant physical discomfort and some disability. Itching and pain can interfere with basic functions, such as self-care, walking, and sleep. Plaques on hands and feet can prevent individuals from working at certain occupations, playing some sports, and caring for family members or a home. The frequency of medical care is costly and can interfere with an employment or school schedule. People with moderate to severe psoriasis may feel self-conscious about their appearance. Psychological distress can lead to depression and social isolation.

What Causes Psoriasis?

Psoriasis is a skin disorder driven by the immune system, especially involving a type of white blood cell called a T cell. Normally, T cells help protect the body against infection and disease. In the case of psoriasis, T cells are put into action by mistake and become so active that they trigger other immune responses, which lead to inflammation and to rapid turnover of skin cells.

In many cases, there is a family history of psoriasis. Researchers have studied a large number of families affected by psoriasis and identified genes linked to the disease.

People with psoriasis may notice that there are times when their skin worsens, called flares, then improves. Conditions that may cause flares include infections, stress, and changes in climate that dry the skin. Also, certain medicines may trigger an outbreak or worsen the disease. Sometimes people who have psoriasis notice that lesions will appear where the skin has experienced trauma. The trauma could be from a cut, scratch, sunburn, or infection.

How Is Psoriasis Diagnosed?

Occasionally, doctors may find it difficult to diagnose psoriasis, because it often looks like other skin diseases. It may be necessary to confirm a diagnosis by examining a small skin sample under a microscope.

There are several forms of psoriasis. Some of these include:

• Plaque psoriasis. Skin lesions are red at the base and covered by silvery scales.
• Guttate psoriasis. Small, drop-shaped lesions appear on the trunk, limbs, and scalp. Guttate psoriasis is most often triggered by upper respiratory infections (for example, a sore throat caused by streptococcal bacteria).
• Pustular psoriasis. Blisters of noninfectious pus appear on the skin. Attacks of pustular psoriasis may be triggered 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. The symptoms may be worsened by friction and sweating.
• Erythrodermic psoriasis. Widespread reddening and scaling of the skin may be a reaction to severe sunburn or to taking corticosteroids (cortisone) or other medications. It can also be caused by a prolonged period of increased activity of psoriasis that is poorly controlled. Erythrodermic psoriasis can be very serious and requires immediate medical attention.

Another condition in which people may experience psoriasis is psoriatic arthritis. This is a form of arthritis that produces the joint inflammation common in arthritis and the lesions common in psoriasis. The joint inflammation and the skin lesions don't necessarily have to occur at the same time.

How Is Psoriasis Treated?

Doctors generally treat psoriasis in steps based on the severity of the disease, size of the areas involved, type of psoriasis, where the psoriasis is located, and the patient's response to initial treatments. Treatment can include:¹

• medicines applied to the skin (topical treatment)
• light treatment (phototherapy)
• medicines by mouth or injection (systemic therapy).

¹All medicines can have side effects. Some medicines and side effects are mentioned in this publication. Some side effects may be more severe than others. You should review the package insert that comes with your medicine and ask your health care provider or pharmacist if you have any questions about the possible side effects.

Over time, affected skin can become resistant to treatment, especially when topical corticosteroids are used. Also, a treatment that works very well in one person may have little effect in another. Thus, doctors often use a trial-and-error approach to find a treatment that works, and they may switch treatments periodically if a treatment does not work or if adverse reactions occur.

Topical Treatment

Treatments applied directly to the skin may improve its condition. Doctors find that some patients respond well to ointment or cream forms of corticosteroids, vitamin D₃, retinoids, coal tar, or anthralin. Bath solutions and lubricants may be soothing, but they are seldom strong enough to improve the condition of the skin. Therefore, they usually are combined with stronger remedies.

Light Therapy

Natural ultraviolet (UV) light from the sun and controlled delivery of artificial UV light are used in treating psoriasis. It is important that light therapy be administered by a doctor. Spending time in the sun or a tanning bed can cause skin damage, increase the risk of skin cancer, and worsen symptoms.

Systemic Treatment

For more severe forms of psoriasis, doctors sometimes prescribe medicines that are taken internally by pill or injection. This is called systemic treatment.

• Methotrexate. Like cyclosporine, methotrexate slows cell turnover by suppressing the immune system. It can be taken by pill or injection. Patients taking methotrexate must be closely monitored because it can cause liver damage and/or decrease the production of oxygen-carrying red blood cells, infection-fighting white blood cells, and clot-enhancing platelets.
• Retinoids. Oral retinoids are compounds with vitamin A-like properties that may be prescribed for severe cases of psoriasis that do not respond to other therapies. Because these medications also may cause birth defects, women must protect themselves from pregnancy.
• Cyclosporine. Taken orally, cyclosporine acts by suppressing the immune system to slow the rapid turnover of skin cells. It may provide quick relief of symptoms, but the improvement stops when treatment is discontinued. Cyclosporine may impair kidney function or cause high blood pressure (hypertension). Therefore, patients must be carefully monitored by a doctor.
• Biologic response modifiers. Biologics are made from proteins produced by living cells instead of chemicals. They interfere with specific immune system processes which cause the overproduction of skin cells and inflammation. These drugs are injected (sometimes by the patient). Patients taking these treatments need to be monitored carefully by a doctor. Because these drugs suppress the immune system response, patients taking these drugs have an increased risk of infection, and the drugs may also interfere with patients taking vaccines. Also, some of these drugs have been associated with other diseases (like central nervous system disorders, blood diseases, cancer, and lymphoma) although their role in the development of or contribution to these diseases is not yet understood.

Combination Therapy

Combining various topical, light, and systemic treatments often permits lower doses of each and can result in increased effectiveness. There are many approaches for treating psoriasis. Ask the doctor about the best options for you. Find out:

• How long the treatment may last.
• How long it will take to see results.
• What the possible side effects are.
• What to do if the side effects are severe.

What Research Is Being Conducted on Psoriasis?

• Skin cell formation. Researchers are trying to learn how skin cells form in order to create healthy skin. At the same time, others are looking at the cells and mechanisms which cause lesions in the skin. If any of these mechanisms can be interrupted, researchers may find a way to stop the disease process.
• Genetics. Significant progress has been made in understanding the inheritance of psoriasis. A number of genes involved in psoriasis are already known or suspected. In a multifactor disease (involving genes, environment, and other factors), variations in one or more genes may produce a greater likelihood of getting the disease. Researchers are continuing to study the genetic aspects of psoriasis and psoriatic arthritis.
• Nervous system. Some researchers are looking at the nervous system to determine what causes pain and itching in psoriasis.
• Immune system. Since discovering that inflammation in psoriasis is triggered by T cells, researchers have been attempting to find ways to quiet immune system reactions in the skin. Among these are studies that try to determine ways to block the activity of T cells or block cytokines (proteins that promote inflammation). If researchers find a way to target only the disease-causing immune reactions while leaving the rest of the immune system alone, resulting treatments could benefit psoriasis patients as well as those with other autoimmune diseases.
• Cardiovascular problems. Research has suggested that psoriasis patients may be at greater risk of cardiovascular problems, especially if the psoriasis is severe, as well as obesity, high blood pressure, and diabetes. Researchers are trying to determine the reasons for these associations and how best to treat patients.

-NIH