Psoriasis

Causes

Autoimmune response

Psoriasis is an autoimmune condition, meaning that it is caused by immune system mistakenly damaging healthy skin cells. It cannot be passed on from one person to another.

Psoriasis occurs when white blood cells produce a number of damaging chemicals in the skin, as if fighting an infection or healing a wound.

In turn, this immune response is thought to trigger changes that cause the skin cells to multiply at an unusually rapid rate. Normally, new skin cells mature and grow on their way to the skin surface, where they eventually flake off and leave the body. This cycle takes 3-4 weeks in healthy skin. However, in skin affected by psoriasis, new skin cells reach the skin surface in 2-6 days. The older skin cells are not able to flake off fast enough and build up in thick, scaly patches.

Formation of dry skin plaques during psoriasis. 

Genetic factors

Four specific genes have been linked to the development of psoriasis: PSOR1, PSOR2, PSOR3 and PSOR4. Changes or variations in the expression of these genes are linked not only to psoriasis, but to other autoimmune conditions such as type 1 diabetes, Graves' disease, coeliac disease and rheumatoid arthritis. As psoriasis tends to run in families, it may be that one or more of these genes are passed down from parents to children.

Environmental factors

Other environmental factors that do not directly cause psoriasis, but can trigger the condition or make your symptoms worse include:

• Skin injury;
• Smoking;
• Infections;
• Cold weather;
• Heavy alcohol consumption, and;
• Stress.

Types

There are several types of psoriasis:

Plaque psoriasis

Also known as psoriasis vulgaris, this is the most common type of psoriasis, accounting for around 80% of all cases. Plaque psoriasis usually appears as raised, inflamed, red patches - called plaques - covered by silvery-white scales. It often develops on the scalp, knees, elbows and lower back.

Guttate psoriasis

Guttate psoriasis often occurs in children or young adults and appears as small red spots on the abdomen, arms and legs. These spots are usually not as thick as the patches that develop in plaque psoriasis. Although the rate of guttate psoriasis is quite low, it is still the second-most common type of psoriasis.

Nail psoriasis

Psoriasis of the fingernails and toenails causes discoloration, abnormal nail growth and a pitted appearance. The nails may also become loose, separate from the nail bed, or crumble.

Scalp psoriasis

This type of psoriasis appears on the scalp as red, itchy, silvery scales that may flake off when the hair is brushed or combed.

Inverse psoriasis

Inverse psoriasis is characterized by smooth, red patches of skin without the scaly plaques. As the condition is aggravated by sweat and friction, symptoms typically affect the groin, genitals, armpits, the skin under the breasts and anywhere else where skin can rub against itself. It also can arise in the skin folds of people who are overweight. Inverse psoriasis is also known as flexural psoriasis or intertriginous psoriasis.

Pustular psoriasis

This type of psoriasis is quite uncommon and usually seen in adults. The condition is characterized by white, pus-filled blisters surrounded by red skin. Pustular psoriasis is often restricted to the palms or soles of the feet, but occasionally can cover a large area of the body.

Erythrodermic psoriasis

Also known as exfoliative psoriasis, this type of psoriasis is the least common. This is a serious condition that requires immediate medical attention. It is characterized by a red, peeling rash across the entire body, which may burn or itch intensely. Erythrodermic psoriasis can be a side effect of severe sunburn or certain medications, such as oral corticosteroids. It may also occur if another type of existing psoriasis is poorly controlled.

Psoriatic arthritis

This painful inflammation of the lining of the joints is caused by the body's damaging immune response to psoriasis. Some estimates suggest that no more than one in five people with psoriasis will develop psoriatic arthritis. The severity differs from person to person, ranging from mild pain and swelling, right through to severe joint damage and disability in two out of five cases. In addition to the usual skin symptoms of psoriasis, psoriatic arthritis is characterized by pain, swelling and stiffness in one or more joints. There may also be pain and redness in the eyes and changes in the nails, such as thickening, discoloration and separation from the skin.

Generalized pustular psoriasis

Also known as von Zumbusch psoriasis, this rare condition is a serious form of pustular psoriasis. It is characterized by large areas of red skin that become painful and tender. Blisters usually form within hours of these initial symptoms and then dry over the next two days. As generalized pustular psoriasis is also accompanied by fever and a toxic reaction, hospitalization is usually required for administration of fluids and antibiotics through a drip.

Signs and symptoms

Psoriasis can range from a few patches of dandruff-like scaling to major outbreaks that cover large areas. The condition also varies in severity from being a mild inconvenience to being disfiguring, disabling and painful.

Symptoms tend to come and go, with the condition flaring for a few weeks to months, then fading or going into complete remission for some time. Psoriasis signs and symptoms vary between individuals, but usually include more than one of the following:

• Red patches of skin covered with silvery scales (plaques);
• Itching, burning or soreness;
• Dry, cracked skin that may bleed;
• Small, scaling spots (more commonly seen in children);
• Thickened, pitted or discolored nails;
• Swollen and stiff joints;
• Inflammation of the eyelid or eyelid lining (conjunctivitis), and;
• Pain (especially in erythrodermic psoriasis, when plaques have been scratched, or in joints affected by psoriatic arthritis).

Methods for diagnosis

A doctor will generally diagnose psoriasis by looking closely at your skin, nails and scalp.

In some cases, the doctor may swab your skin or take a small tissue sample (biopsy) for closer inspection under a microscope. These tests may help to determine the type of psoriasis and also rule out other skin conditions.

Types of treatment

As there is no cure for psoriasis, the aim of treatment is to control symptoms and prevent infection. The choice of treatment will depend on the severity of the condition and how the skin responds to different medications. A doctor may suggest one or more of the following treatment options:

Self care

Avoiding triggers

Triggers for psoriasis should be identified in consultation with a doctor so that they can be avoided. For example, if smoking makes symptoms worse, exposure to cigarette smoke could be limited or avoided.

Personal care

Bathing every day with lukewarm water and mild soap can help to remove scales and reduce inflammation. Drying carefully, moisturizing, and putting on loose, smooth clothing after bathing may also help to prevent irritation.

Your doctor may also suggest applying an oil-rich moisturizer and then wrapping the affected skin with plastic wrap overnight to help relieve redness and scaling. To avoid scratching, additional measures could include keeping the nails short, wearing cotton gloves at night or covering the affected area with a dressing.

Lifestyle

To manage your psoriasis, a healthy diet rich in fruit, vegetables and wholegrains and low in alcohol is usually recommended. While there is no specific link between certain foods and psoriasis, alcohol is known to aggravate psoriasis and reduce the effectiveness of some treatments.

A doctor may also encourage outdoor activities or controlled sunbathing to improve symptoms through safe, moderate exposure to sunlight. However, while exposure to sunlight or ultraviolet (UV) light is usually helpful, it can also cause a flare-up of symptoms in a small number of people. When this occurs, the condition is known as photosensitive psoriasis. Unlike other types of psoriasis, it improves in winter and gets worse in summer.

Medications

Creams, lotions and ointments

The choice of creams, lotions and ointments (collectively known as emollients), used by your doctor, may depend on the location and severity of symptoms. They help soften the skin and keep it moist under a protective layer. Common emollients include paraffin preparations, sorbolene, aqueous creams and bath oils.

Corticosteroids

If the skin is inflamed, a corticosteroid cream may be prescribed for application directly onto the skin. For mild to moderate cases, hydrocortisone or clobetasone butyrate are common corticosteroid medications. For severe symptoms or stubborn plaques, a stronger option may be recommended. Corticosteroid foams and solutions are also available to treat psoriasis on the scalp.

Corticosteroids are used to quickly reduce inflammation, block new skin cell production and relieve itching. When applied as a cream, side-effects can include thinning of the skin, acne and red skin sores.

In cases where symptoms do not respond to creams, a doctor may inject corticosteroid medication, such as triamcinolone acetonide, directly into the plaques.

Other medications

Some other medications commonly prescribed for initial treatment of psoriasis include creams or ointments containing coal tar, dithranol (also known as anthralin), or a derivative of vitamin A (retinoids) or vitamin D.

Tazarotene is a common vitamin A derivative used to treat psoriasis, while calcipotriene, calcitriol and tacalcitol are examples of vitamin D derivatives. Creams to remove scaling may contain salicylic acid or lactic acid.

Light therapies

Also known as phototherapies, these treatments are generally recommended when symptoms are widespread or when previous treatments have not been effective. They may be used alone or together with other medications. Light therapies used in the treatment of psoriasis include:

Ultraviolet B (UVB) therapies

An early form of UVB phototherapy, known as broadband UVB therapy, involves controlled application of UVB light to the skin from an artificial light source. This treatment causes mild burning as a side-effect, characterized by redness, itching and dry skin.

A more recent version of UVB treatment, called narrow-band UVB therapy, is more effective, but causes more severe burning. Nevertheless, it is the most commonly used light therapy to treat psoriasis.

Photodynamic therapy

Also known as psoralen plus ultraviolet A (PUVA), photodynamic therapy involves taking the light-sensitizing medication, psoralen, prior to application of ultraviolet A (UVA) light. This treatment is usually given 2-3 times per week, with additional treatments every 2-4 weeks, until the condition clears. UVA light penetrates the skin more deeply than UVB light. While this makes it more effective, photodynamic therapy is used sparingly due to the risk of skin cancers.

Laser therapies

A device, known as an excimer laser, may provide more effective treatment than narrowband UVB therapy in certain people with mild to moderate psoriasis. Using this laser, a very precise area of skin can be targeted.

Another type of device, called a pulsed-dye laser, gives off a high-intensity light that destroys the tiny blood vessels (capillaries) in the skin affected by psoriasis. The pulsed-dye laser is also used in cosmetic procedures, such as removal of birthmarks and skin redness.

Oral or injected medications

If initial treatments do not work, a doctor may prescribe an oral or injected medication that works throughout the entire body. When medications are given in this way, they are known as systemic medications.

Some examples of systemic medications include methotrexate, cyclosporin, and infliximab. These medications have powerful effects on the immune system and can produce serious side-effects. For this reason, they are usually only prescribed by a specialized doctor (dermatologist or rheumatologist).

Potential complications

A number of complications can arise from psoriasis depending on the type, severity and location of the symptoms. Complications can include:

Heart disease

Psoriasis has been linked to an increased risk of heart conditions including heart attack, hardening of the arteries (atherosclerosis), high blood pressure (hypertension), diabetes and stroke.

Folate deficiency

Severe cases of psoriasis may lead to low levels of folate, a B-group vitamin that is important in blood cell formation and prevention of birth defects.

Cancer

In severe cases of psoriasis, a family of medications known as immunomodulators (or calcineurin inhibitors) may be prescribed. These medications are only used sparingly as they have been shown to increase the chance of developing cancers of the skin and of the lymph nodes. There is also evidence to suggest that long-standing, severe psoriasis is linked to a higher risk of developing cancers, which is not directly related to any treatment.

Poor body temperature regulation

The peeling rash that occurs in cases of erythrodermic psoriasis can disrupt the ability of the skin to act as a natural barrier and temperature regulator. As a result, people with this type of psoriasis may have problems with controlling normal body temperature.

Psychological effects

For some people, severe or long-term symptoms may affect quality of life or result in psychological issues, such as depression, distress, low self-esteem or embarrassment.

Prognosis

There is no cure for psoriasis, but the condition can be treated and may go into remission for a long time before returning. With effective treatment, it often does not affect general health, although in some cases, psoriatic arthritis may develop.

Prevention

While there is no way to prevent psoriasis, steps may be taken to decrease the chances of symptoms returning or worsening. In general, these steps closely resemble the self-care treatment options, which include good skin maintenance habits and avoiding factors that trigger psoriasis. Daily baths or showers are usually recommended, but harsh soaps or excessive scrubbing can irritate the skin.