Psoriasis

Definition
Psoriasis is a chronic skin disease generally characterized by patches of raised, red skin covered by silvery white scales. Psoriasis can develop anywhere on the body, but the scalp, knees, elbows, torso and nails are most commonly affected. The severity of the disease can vary from a few small patches to large areas of affected skin.

Causes/associated factors
The exact cause of psoriasis is unknown, but recent research indicates that it may be related to a defect in the skin's immune system. The immune system includes a type of white blood cell called a T cell. This cell normally helps protect the body against infection and disease. With psoriasis, an immune system malfunction causes activity in the T cells of the skin that trigger inflammation and excessive skin cell reproduction. Psoriasis also has a genetic link, which means it can be hereditary. It is not contagious.
People who have psoriasis often experience periods of time when their symptoms improve and then worsen. Internal or external conditions, known as "triggers," can cause flare-ups. Common triggers include:

emotional stress
skin injuries (including sunburn)
infection
climate changes
reactions to certain drugs (particularly beta blockers and lithium)
heavy alcohol consumption

Signs/symptoms
There are several forms of psoriasis. The most common is plaque psoriasis, which is characterized by itchy or painful, slightly raised areas or plaques of red skin covered by silvery white scales. This occurs when cells in the outer layer of skin reproduce faster, every three to four days (normal skin cells mature in 28 to 30 days) and accumulate on the skin's surface. Fingernails and toenails can also be affected, causing discoloration, splitting and pitting in the nail surface.
Other forms of psoriasis include:

pustular, characterized by small blisters of pus, which may weep
inverse, characterized by dry, smooth red plaques in skin folds (such as the genitals, under the breasts and the armpits)
erythrodermic, characterized by widespread sloughing and inflammation of the skin
guttate, characterized by small, droplike lesions

Diagnosis
Psoriasis is usually diagnosed by a doctor based on a physical exam. A skin biopsy (taking a tissue sample for further evaluation under the microscope) may be done to confirm the diagnosis, but is usually not necessary.
Treatment
There is no cure for psoriasis, but many treatment options are available. The goal of treatment is to ease discomfort and slow the production of skin cells. It may take time to find which treatment methods work best for you. Also, your treatment may be changed periodically if you become resistant to the current treatment or experience unfavorable side effects.

Your doctor may recommend one of the following treatment methods based on the severity of symptoms and the type of psoriasis you have. The treatments may be used alone or in combination with one another.

Topicals
Topical ointments, creams or lotions are usually the first treatment method recommended for mild to moderate forms of psoriasis. These are available in different strengths, some without a prescription. Common topical preparations include:

emollients such as petroleum jelly and lactic acid lotions or creams
corticosteroids
topical retinoids
calcipotriene (a manufactured form of vitamin D3)
coal tar
anthralin
salicylic acid
Phototherapy
Treatment with ultraviolet (UV) light is known as phototherapy, which uses natural or artificial light. Many people find their symptoms improve with regular, short (nonburning) doses of sunlight. If you live in a cold climate or need a more controlled form of light, artificial light may be recommended. A light panel or box fitted with bulbs that emit ultraviolet waves may be used.

Photochemotherapy, also known as PUVA, is a combination of the medication psoralen along with exposure to ultraviolet A (UVA) light. This treatment can be given in the doctor's office. Psoralen, which is available in a pill or topical form, makes the body more sensitive to light. Like any form of therapy, light therapy can have side effects that your doctor will discuss with you.

Systemic
Systemic treatment is reserved for more severe forms of psoriasis. Systemic treatments are given orally or by injection. These drugs act by suppressing the immune system. Because of the potential side effects, close supervision of your response to the treatment is essential. Systemic treatments include:

methotrexate
cyclosporine
systemic retinoids
etanercept
alefacept

Complications
Skin provides an important barrier against infection. A secondary infection may potentially develop whenever you have a crack or opening in the skin. This can become a major concern in cases of moderate to severe forms of psoriasis when large areas of skin are involved.
Between 10 and 30 percent of people who have psoriasis also develop psoriatic arthritis, a joint disease similar to rheumatoid arthritis. Psoriatic arthritis often affects the joints at the ends of fingers and toes, and is accompanied by changes in the nails. It can also affect the wrists, neck, lower back, knees and ankles.


Pregnancy-specific information
The hormonal changes associated with pregnancy may affect psoriasis. Some women notice an improvement in their symptoms during pregnancy. Make sure the doctor treating you for psoriasis is aware that you're pregnant. Some of the medications used to treat psoriasis may be harmful to your unborn baby.

Senior-specific information
Although psoriasis is most common between ages 15 and 35, it can develop at any age. Be sure to notify your doctor of any changes in your skin.