psoriasis

The disorder is a chronic or recurring condition which can vary in severity, from minor localised patches to complete body coverage. Psoriasis can also cause inflammation of the joints. Ten to fifteen percent of people with psoriasis have psoriatic arthritis.

Several factors are thought to aggravate psoriasis. Individuals with psoriasis may also suffer from depression and loss of self-esteem. There are many treatments available but because of its chronic recurrent nature psoriasis is a challenge to treat.

History

Psoriasis is probably one of the longest known illnesses of humans and simultaneously one of the most misjudged and misunderstood. Some scholars believe psoriasis to have been included among the skin conditions called tzaraat in the Bible. In more recent times psoriasis was frequently described as a variety of leprosy.

It was during the 20th century that psoriasis was further differentiated into specific types.

Types of psoriasis

The symptoms of psoriasis can manifest in a variety of forms. Variants include plaque, pustular, guttate and flexural psoriasis.

Plaque psoriasis (psoriasis vulgaris) (L40.0) is the most common form of psoriasis. It affects 80 to 90% of people with psoriasis. Plaque psoriasis typically appears as raised areas of inflamed skin covered with silvery white scaly skin.

Flexural psoriasis (inverse psoriasis) (L40.83-4) appears as smooth inflamed patches of skin.

Guttate psoriasis (L40.4) is characterized by numerous small oval (teardrop-shaped) spots. These numerous spots of psoriasis appear over large areas of the body, such as the trunk, limbs, and scalp. Guttate psoriasis is associated with streptococcal throat infection.

Pustular psoriasis (L40.1-3, L40.82) appears as raised bumps that are filled with non-infectious pus (pustules). Pustular psoriasis can be localised, commonly to the hands and feet (palmoplantar pustulosis), or generalised with widespread patches occurring randomly on any part of the body.

Nail psoriasis (L40.86) produces a variety of changes in the appearance of finger and toe nails.

Psoriatic arthritis (L40.5) involves joint and connective tissue inflammation. About 10-15% of people who have psoriasis also have psoriatic arthritis.

Erythrodermic psoriasis (L40.85) involves the widespread inflammation and exfoliation of the skin over most of the body surface. It is often the result of an exacerbation of unstable plaque psoriasis, particularly following the abrupt withdrawal of systemic treatment. This form of psoriasis can be fatal, as the extreme inflammation and exfoliation disrupt the body's ability to regulate temperature and for the skin to perform barrier functions.

Diagnosis

A diagnosis of psoriasis is usually based on the appearance of the skin. There are no special blood tests or diagnostic procedures for psoriasis.

Severity

Psoriasis is usually graded as mild (affecting less than 3% of the body), moderate (affecting 3-10% of the body) or severe. Several other scales exist for measuring the severity of psoriasis.

The Psoriasis Area Severity Index (PASI) is the most widely used measurement tool for psoriasis.

Effect on the quality of life

Psoriasis has been shown to affect health-related quality of life to an extent similar to the effects of other chronic diseases such as depression, myocardial infarction, hypertension, congestive heart failure or type 2 diabetes.

Individuals with psoriasis may also feel self-conscious about their appearance and have a poor self-image that stems from fear of public rejection and psychosexual concerns.

Epidemiology

Psoriasis affects both sexes equally and can occur at any age, although it most commonly appears for the first time between the ages of 15 and 25 years.

The prevalence of psoriasis in Western populations is estimated to be around 2-3%. A survey conducted by the National Psoriasis Foundation (a US based psoriasis education and advocacy group, which is partly funded by pharmaceutical companies) found a prevalence of 2.1% among adult Americans. The study also found that 35% of people with psoriasis could be classified as having moderate to severe psoriasis.

Around one-third of people with psoriasis report a family history of the disease, and researchers have identified genetic loci associated with the condition. Studies of monozygotic twins suggest a 70% chance of a twin developing psoriasis if the other twin has psoriasis. These finding suggests both a genetic predisposition and an environmental response in developing psoriasis.

Onset before age 40 usually indicates a greater genetic susceptibility and a more severe or recurrent course of psoriasis.

Cause

The cause of psoriasis is not fully understood. The first considers psoriasis as primarily a disorder of excessive growth and reproduction of skin cells.

The immune-mediated model of psoriasis has been supported by the observation that immunosuppressant medications can clear psoriasis plaques. However, the role of the immune system is not fully understood, and it has recently been reported that an animal model of psoriasis can be triggered in mice lacking T cells. Animal models, however, reveal only a few aspects resembling human psoriasis.

Psoriasis is a fairly idiosyncratic disease. The majority of people's experience of psoriasis is one in which it may worsen or improve for no apparent reason. Studies of the factors associated with psoriasis tend to be based on small (usually hospital based) samples of individuals. Excessive alcohol consumption, smoking and obesity may exacerbate psoriasis or make the management of the condition difficult.

Treatment

There can be substantial variation between individuals in the effectiveness of specific psoriasis treatments. The decision to employ a particular treatment is based on the type of psoriasis, its location, extent and severity.

Medications with the least potential for adverse reactions are preferentially employed. Medications with significant toxicity are reserved for severe unresponsive psoriasis. This is called the psoriasis treatment ladder.

Over time, psoriasis can become resistant to a specific therapy.

Topical treatment

Bath solutions and moisturizers help sooth affected skin and reduce the dryness which accompanies the build-up of skin on psoriasis plaques. Medicated creams and ointments applied directly onto psoriasis plaques can help reduce inflammation, remove built-up scale, reduce skin turn over, and clear affected skin of plaques.

The disadvantages of topical agents are variabily that they can often irritate normal skin, can be awkward to apply, cannot be used for long periods, can stain clothing or have a strong odour.

Some topical agents are used in conjunction with other therapies, especially phototherapy.

Phototherapy

It has long been recognised that daily, short, nonburning exposure to sunlight helped to clear or improve psoriasis.

Sunlight contains many different wavelengths of light. It was during the early part of the 20th century that it was recognised that for psoriasis the therapeutic property of sunlight was due to the wavelengths classified as ultraviolet (UV) light.

Ultraviolet wavelengths are subdivided into UVA (380–315 nm), UVB (315–280 nm), and UVC (< Ultraviolet B (UVB) (315–280 nm) is absorbed by the epidermis and has a beneficial effect on psoriasis. Narrowband UVB (311 to 312 nm), is that part of the UVB spectrum that is most helpful for psoriasis. Exposure to UVB several times per week, over several weeks can help people attain a remission from psoriasis.

Ultraviolet light treatment is frequently combined with topical (coal tar, calcipotriol) or systemic treatment (retinoids) as there is a synergy in their combination.

Photochemotherapy

Psoralen and ultraviolet A phototherapy (PUVA) combines the oral or topical administration of psoralen with exposure to ultraviolet A (UVA) light.

Dark glasses must be worn during PUVA treatment because there is a risk of cataracts developing from exposure to sunlight.

Systemic treatment

Psoriasis which is resistant to topical treatment and phototherapy is treated by medications that are taken internally by pill or injection. Most people experience a recurrence of psoriasis after systemic treatment is discontinued.

The three main traditional systemic treatments are the immunosupressant drugs methotrexate and ciclosporin, and retinoids, which are synthetic forms of vitamin A. Other additional drugs, not specifically licensed for psoriasis, have been found to be effective. These have all been used effectively to treat psoriasis when other treatments have failed. Although not licensed in many other countries fumaric acid esters have also been used to treat severe psoriasis in Germany for over 20 years.

Biologics are manufactured proteins that interrupt the immune process involved in psoriasis. Unlike generalised immunosuppressant therapies such as methotrexate, biologics focus on specific aspects of the immune function leading to psoriasis. They are very expensive and only suitable for very few patients with psoriasis.

Alternative Therapy

Historical Treatment

The history of psoriasis is littered with treatments of dubious effectiveness and high toxicity.

In the more recent past Fowler's solution, which contains a poisonous and carcinogenic arsenic compound, was used by dermatologists as a treatment for psoriasis during the 18th and 19th centuries. Grenz Rays (also called ultrasoft X-rays or Bucky rays) was a popular treatment of psoriasis during the middle of the 20th century.

Future drug development

Historically, agents used to treat psoriasis were discovered by experimentation or by accident. In contrast, current novel therapeutic agents are designed from a better understanding of the immune processes involved in psoriasis and by the specific targeting of molecular mediators.

Research into antisense oligonucleotides is in its infancy but carries the potential to provide novel theraputic strategies for treating psoriasis.

Prognosis

Psoriasis is a chronic lifelong condition. Many of the most effective agents used to treat severe psoriasis carry an increased risk of significant morbidity including skin cancers, lymphoma and liver disease. However, the majority of people's experience of psoriasis is that of minor localised patches, particularly on the elbows and knees, which can be treated with topical medication. Psoriasis does get worse over time but it is not possible to predict who will go on to develop extensive psoriasis or those in whom the disease may appear to vanish.

"The heartbreak of psoriasis"

The phrase "the heartbreak of psoriasis" is often used both seriously and ironically to describe the emotional impact of the disease.

Notable people who have had psoriasis