Family doctor

WHAT IS PSORIASIS?

Psoriasis is a common skin disorder affecting at least 2% of the population. Although it does not affect physical health it can have an enormous psychological impact. Fortunately there are a wide range of effective treatments and some exciting new developments on the horizon.

Psoriasis can occur at any age. There is a case report of someone developing it for the first time at 101 years of age! Each individual case is different even in the same family. Once psoriasis has appeared there is no cure. It may however disappear for long periods but can always reappear at some stage. It is not a progressive disease and is quite unpredictable in its course.

Psoriasis typically appears as scaly thickened areas of skin particularly on the scalp, tips of the elbows and knees, but can affect just about anywhere. Sometimes it can be quite localised for example to hands and feet or groin. It can affect finger and toenails. About 6% of psoriasis sufferers have arthritis associated but otherwise it has no internal effects.

The exact cause of psoriasis remains a mystery. There can be a genetic predisposition to psoriasis although many cases occur without a family history. There is overactivity of the immune system and an accelerated growth of the epidermis (top skin layer) with abnormalities of keratin (skin protein) production. Stress often aggravates the condition. Minor injury to the skin including sunburn can also trigger a flare. Diet has not been shown to play a role.

These may be divided into three main groups:

These are safe but can be messy. Often much of the treatment can be done at night for convenience.

Tar therapy - it has been known since ancient Egyptian times that tar helps psoriasis although we still don‚Äö?Ñ?¥t fully understand why. Tars are often combined with steroid creams and salicylic acid to remove scale. Over-the-counter tar preparations can help mild psoriasis.

Daivonex (calcipitriol) - is a derivative of Vitamin D. It can be very helpful in some cases although some find it irritating.

Topical steroids - are used particularly in itchy inflamed psoriasis. They can thin the skin if overused and may in some cases actually feed the psoriasis, so should only be used under supervision.

Dithranol cream - can be used for thick stubborn psoriasis particularly on arms and legs. It is applied for only 30 minutes at a time and can be irritating.

Ninety percent of psoriasis sufferers improve with UV light exposure. This includes sunlight, sunbeds, home UVB machines and special UV light machines managed by dermatologists. The last option is the most effective. Both UVB and PUVA can be used. The latter involves taking pills to sensitise skin to the light. Too much UV exposure increases the risk of skin cancer.

These are the most effective treatments for psoriasis but also have the most side effects. There are three main drugs used. All require specialist supervision. None offer a permanent cure.

Acitretin (Neotigason) - This is a Vitamin A derivative (retinoid) related to the drug Roaccutane used in treating severe acne. It can be very effective in selected cases. Side effects include dry skin and lips and sun sensitivity. Pregnancy must be avoided.

Methotrexate - is used once weekly and can totally control severe psoriasis. It is particularly good in cases with arthritis associated. There is a small risk of liver damage and a liver biopsy periodically is recommended.

Cyclosporin - is an immune suppressing drug that has revolutionised organ transplantation. It can be very effective in severe psoriasis. Blood pressure and kidney function must be watched during treatment.

Sometimes an admission to a dermatology unit for tar and daily ultraviolet light treatments can be very effective. The break from day to day stresses is probably part of the benefit.

While it is unlikely that psoriasis will ever be cured, new topical and oral drugs continue to appear and add to the arsenal of weapons against psoriasis. There is interesting work being done on a vaccine for psoriasis, and although early studies are promising it is too early to know what role this may have.

The following pictures depict psoriasis at different sites on the body:

Psoriasis of the scalp.

Psoriasis of the knee.

Psoriasis of the hands.

Psoriasis covering the body.