Psoriasis is a common skin disorder affecting 1 - 2% of the population. It ranges from very mild, almost unnoticeable, to very severe disabling conditions. It occurs equally in men and women, at any age, and tends to come and go unpredictably. It is not infectious, and does not scar the skin.

The usual age of onset is after 20 years old, but for those with a positive family history, it can be as early as below 10 years old.

Although there is no cure for psoriasis, but with the appropriate treatments, it is very possible to control the disease to the minimum, with the least adverse effect on the patient’s life.

The underlying problem in the cellular level is a disordered cell division and migration process. The skin cells in the basal layer change gradually as they move towards the surface where they are continually shed. This process normally takes between 3 and 4 weeks. In psoriasis, the rate of turnover is dramatically increased to as little as 3 or 4 days. The reasons for this are still not fully understood, but there is certainly a genetic component, which is expressed by some unknown environmental factors.

Clinical Types & Signs

Chronic Plaques Psoriasis

It accounts for over 90% of psoriasis. It is red, thick and covered with silvery white scales. They can take up a variety of shapes and sizes, and have well defined edges from the surrounding skin.

These plaques are distributed mainly on the trunk, scalp, and the outside of the limbs, particularly the knees and elbows. Those on the limbs are usually symmetrical. In the scalp, the scales heap up so that the underlying redness is hard to see.

In the beginning it is mild with only one or two plaques, and becomes more obvious and numerous after a number of years. Only 20% may experience some degree of itch, others do not have any feeling. The severity may vary from time to time, while in the summer it usually improves somewhat because of the ultraviolet light exposure.

Some come up where the skin has been damaged and this is known as the Köbner phenomenon.

Acute Guttate Psoriasis

It is seen most often in children and is sometimes triggered by a sore throat 1 – 2 weeks prior to the onset of psoriasis. The patches are usually small, often less than 1 cm across, but numerous. Again there are some fine white scales on the surface, and it is not difficult to diagnose, although it can be confused with Pityriasis Vesicolor or Pityriasis Rosea. The patches are sometimes itchy.

Acute guttate psoriasis usually disappears after a few months, but may recur when the throat is again infected with streptococci. It is not uncommon to turn to chronic plaques psoriasis some years later.

Flexural Psoriasis

In contrast to chronic plaques psoriasis in other areas, when in body folds such as the armpits or under the breasts, the red well-defined areas are easy to see but are seldom scaly because of the trapped moisture.

Localized Psoriasis

It affects local areas on the scalp, the palms, the soles, or the nails.

Scalp: lots of large and thick scales. Initially they are smaller and may be confused with seborrhoeic dermatitis.

Palms and soles: the skin is very thick and rough, the dryness causes cracks and can be very painful.

Nails: irregular pitting of the surface of the nail, the colour may turn yellow and the nail is very thickened, the nail may separate from the nail bed, and the surface may peel in flakes. These may be confused with fungal infection of the nails.

Erythrodermic Psoriasis

The skin of the whole body is red, dry and inflamed. This is unstable psoriasis and can be dangerous and the patient needs to be admitted to hospital for systemic therapy.

Local Pustular Psoriasis

It involves only the palms and soles, where the red areas are studded with a mixture of new yellow pus spots and older brown dried up pus spots. This is slow to clear and often responds poorly to treatment.

Generalized Pustular Psoriasis

This is usually due to the sudden withdrawal of oral steroid in someone who needs to take it for another reason. Sometimes pregnancy may be a precipitating factor too. There are wide spread pustules, causing pain, and burning sensation. This is a serious complication and is dangerous; again the patient needs to be admitted to hospital for systemic therapy.

Joint Psoriasis

Very few psoriasis cases affect the joints alone, but it can happen without any signs on the skin itself. This usually affects the large joints such as the knees, elbows, or shoulders.

Diagnosis

Psoriasis is usually easy to recognise by the features on the skin, scalp, and nails. If a definitive diagnosis is required, a biopsy can be done by cutting off a very small piece of skin for laboratory analysis.

X rays examinations may find out some typical changes, and would help in arriving the diagnosis when only the joints are affected.

Management & Treatments

Psoriasis cannot be cured. However, treatment to control the signs and symptoms is usually effective. The skin becomes less scaly and may then look completely normal.

There are many different treatment methods available; each has its good and bad points. This will depend on the type of psoriasis and on its severity. Also, when deciding on the treatments, the doctor and the patient need to discuss them in details so as to arrive at a regime that will take into account the patient’s life style, occupation and family circumstances.

Attention is required in some factors outside the usual treatment regime:

• Ultra violet light usually makes psoriasis better, but rarely can make it worse. Over exposure may cause sunburn, which is an injury that can lead to new areas of psoriasis when it heals.
• Some medicines may make psoriasis worse, and the doctor’s advice is required when taking new medicines. These include Lithium, Aspirin, Iodides, and Beta-blockers.
• Alcohol is best avoided, because it can stimulate the onset of psoriasis. Alcohol also causes liver damages, which may prevent the patient from receiving some treatments when necessary.

Topical Therapies

1. Topical Steroid

It is widely used because of its simplicity and efficacy. Weaker steroids often do not work very well on thick patches of psoriasis, but may do better on the face or in the skin folds. The stronger ones have side effects, one of which is to make the skin thinner. Psoriasis sometimes comes back quickly when topical steroid treatment stops.
Therefore the strong preparations are usually avoided by the doctors.

There is also steroid solution available for application on the scalp. The penetration is better if mixed together with salicylic acid.

2. Vitamin D analogues

Recently, two new vitamin D3 preparations, calcipotriol and tacalcitol, have been introduced. They are safe and cosmetically acceptable. They are mainly used in chronic plaques psoriasis.

Treatment is applied either once (tacalcitol) or twice a day (calcipotriol) and can go on for as long as required. Irritation may occur, especially on the face, bottom and genitals. Treatment should be applied to those areas only on the specific instructions of the doctor.

3. Emollient

The purpose is to keep the skin softer and improve the external appearance by removing the flaky scales. 10% urea has a good effect and can be purchased easily from the chemist.

4. Tar preparations

This is a very traditional treatment and is divided into pine tar and coal tar. Coal tar is better for stable chronic plaques psoriasis, but the effect is slower than steroid or calcipotriol.

It used to be done as a tar bath in the hospital out-patient clinic, followed by wrapping the skin with gauze, or photo-therapy. This method is messy, can stain clothing, and requires a lot of medical labour, and is no longer a popular treatment.

Coal tar paste can be applied to the plaques but again is smelly and messy. Now the tar preparations have been improved in the texture and smell, with cream and gel form. Shampoo is also available for washing the hair in scalp psoriasis.

5. Dithranol

This can be used for minor or moderate chronic plaques psoriasis. The strength of the dithranol is gradually increased every 3-5 days, from 0.01% to a maximum of 1%.

Dithranol is often used as short contact therapy, being applied only to areas of psoriasis, and washed off after 30 to 60 minutes. If the areas being treated become inflamed, treatment should stop until this settles, but may then be resumed at a lower concentration. As your psoriasis clears, the treated areas will gradually stain brown. The staining goes away over the next couple of weeks. Many patients can clear their psoriasis in 6 weeks.

Occasionally dithranol irritates the skin, making it inflamed and sore. The face should not be treated, as contact with the eyes must be avoided and staining may be unsightly. Dithranol stains not only the skin and clothing, but baths and showers as well. The latter should be cleaned immediately to avoid permanent staining.

6. Vitamin A analogues

Tazarotene is a vitamin A gel that is applied once daily to patches of psoriasis. Irritation may occur if it is applied to the face or skin folds. It must not be used during pregnancy.

Oral Therapies

1. Vitamin A analogues

Acitretin can be used for moderately severe psoriasis not responding to topical treatments. It is particularly useful for generalised pustular psoriasis. It has a synergistic effect if used together with phototherapy.

It can cause severe birth defects; women must avoid pregnancy for at least six months after taking the medication.

It may cause an increase an increase in the liver enzymes and triglycerides levels, and blood tests are required for this every month. If taking it for longer than a few years, the bone may be abnormally thickened. Other side effects include dryness of the skin, lips, eyes, and even the inside of vagina.

2. Methotrexate

This is taken only once a week, with good effect on different types of psoriasis including the joint psoriasis.

The main side effect is liver damage, and regular blood tests are required to check the liver enzymes levels. When an accumulative dose of 1.5g is reached, a liver biopsy is needed to check for early cirrhosis. The treatment needs to be stopped when this happens.

Those with kidneys problems may excrete the drug more slowly and accordingly a lower dosage should be taken. Other side effects include anaemia, reduction of white blood cells, hair loss and rash. Again, methrotrexate may cause birth defects, and women should discontinue it for at least 3 months before getting pregnant

3. 5-Hydroxyurea

This medication is not as effective as cyclosporine or methotrexate, but unlike the stronger drugs it can be used with phototherapy treatments. Another advantage is that it can be used in patients with some liver damage. Possible side effects include anemia and a decrease in white blood cells and platelets. It should not be taken by women who are pregnant or planning to become pregnant.

4. Cyclosporin A

Cyclosporine works by suppressing the immune system and is similar to methotrexate in effectiveness. Like other immunosuppressant drugs, cyclosporine increases the risk of infection. Other side effects include overgrowth of gum, kidney problems and high blood pressure, the risk increases with higher dosages and long-term therapy.

Phototherapy

This term refers to treatment with various forms of ultraviolet light, sometimes assisted by taking particular tablets. It is helpful if the psoriasis is extensive, or fails to clear with topical treatment or comes back quickly after seeming to clear. Topical therapy will usually continue during the phototherapy.

1. UVB Phototherapy

Artificial sources of UVB light are similar to sunlight. Some physicians will start with UVB treatments instead of topical agents. UVB phototherapy also is used to treat widespread psoriasis and lesions that resist topical treatment. UVB phototherapy also may be combined with other treatments. One combined therapy program, referred to as the Ingram regime, involves a coal tar bath, UVB phototherapy, and application of an anthralin-salicylic acid paste, which is left on the skin for 6 to 24 hours. A similar regime, the Goeckerman treatment, involves application of coal tar ointment and UVB phototherapy.

Because UV exposure may increase the risk of skin cancer, it needs to be followed up carefully and the total accumulative doses of UVB should be recorded.

2. PUVA

This treatment combines oral or topical administration of a medicine called psoralen a couple of hours before exposure to ultraviolet A light (P + UVA). Psoralen makes the body more sensitive to UVA light. PUVA is normally used when more than 10 percent of the body's skin is affected or when rapid clearing is required.

Compared with daily UVB treatment, PUVA treatment two to three times per week clears psoriasis more consistently but less quickly. After 15 – 25 treatments, it can be reduced to maintenance of one treatment every 1 to 2 weeks. When the psoriasis recurs again, a new cycle of treatment can be started again.

It is associated with more side effects, including nausea, headache, fatigue, burning, and itching. Long-term treatment is associated with irregular skin pigmentation. Researchers have found that PUVA is effective and relatively safe when combined with some oral medications (retinoids and hydroxyurea), but appears to be associated with skin cancer when combined with other oral medications (methotrexate or cyclosporine). The patient needs to wear protective goggles during treatment to prevent the happening of eye damages and cataracts

Immunomodulator drugs (biologics)

Biologics work by blocking interactions between certain immune system cells. They have strong effects on the immune system and may pose many of the same risks as other immunosuppressant drugs. They are approved for the treatment of moderate to severe cases of psoriasis, which has failed to respond to traditional therapy, or for people with associated psoriatic arthritis.

They include alefacept, efalizumab, etanercept and infliximab. These drugs are given by intravenous infusion, intramuscular or subcutaneous injection.