Dr Colin Theng, Consultant Dermatologist at the National Skin Centre, gives AsiaOne the facts on this chronic inflammatory skin condition that affects 40,000 Singaporeans.

What is psoriasis?

Psoriasis is a chronic inflammatory skin condition. It presents with inflamed, scaly lesions that can itch, crack and bleed, and can be disfiguring. This commonly occurs on the scalp, elbow and back and shin although any part of the body may be affected.

Daily activities that most people take for granted, such as going for a swim, can be difficult for psoriasis patients. What's more, studies have shown that up to 30 percent of people with psoriasis also develop psoriatic arthritis - a painful disease that causes stiffness and swelling in and around the joints.

Psoriasis is an incurable skin disorder, although many treatments are available that can result in excellent control of the disease.

It is now known that the immune system plays an important part in the pathogenesis of the disease. The T cells which are a type of white blood cells are activated and cause release of chemicals called cytokines which result in the inflammation of the skin. This leads to the skin cells regenerating too quickly resulting in psoriasis.

In Singapore, it is estimated that at least 40,000 people have psoriasis. Globally, psoriasis affects about 125 million people.

Who are likely to be affected by psoriasis? Is it hereditary?

There are two peaks age groups in which psoriasis first presents and these are the 20s-30s age group and 50-60s. While the exact cause of psoriasis is unknown, genetic factors do play an important part in the disease. The disease is seen to run in some families and twin studies have shown up to 70% concordance rate in identical twins.

Environmental factors also play an important role and these factors may influence the expression of the genes and it is likely that an interplay of genetic and environmental factors lead to the expression of the disease.

Is there any way to prevent psoriasis?

There is no way to prevent psoriasis. We do know, however, that several factors may aggravate the disease. Some of these triggers include emotional stress, some types of infection, or reaction to certain drugs. By avoiding these triggers, psoriasis exacerbations may be prevented.

What are the common treatments for psoriasis in Singapore ?

Psoriasis and psoriatic arthritis have no cure, but many different therapies are available to control the disease. Existing treatments have had some success but often have undesirable side effects.

In recent years, the arrival of biologic treatment agents has revolutionised psoriasis treatment.

Biologics agents are developed from latest bioengineering technology and target specific pathways of the immune system. By inhibiting these specific immune pathways, they result in a decrease in the inflammatory process and control of the disease.

An example of a biologic agent is Etanercept, which is the latest biologic agent to receive HSA approval in Singapore for the treatment of psoriasis. The main advantage of the biologic agents is the relative lack of end-organ toxicity such as kidney and liver toxicity compared with the traditional systemic treatments.

However, side effects of biologic treatment include an increased susceptibility to infections.

As for existing treatments,topical medications are most commonly prescribed. They are usually used in the treatment of mild disease and include topical steroids as well as coal tar.

Systemic treatments such as phototherapy (ultraviolet radiation) and oral medications are usually reserved for patients with moderate to severe disease or those who do not respond well to the topical medications.

Phototherapy is an effective treatment but requires the patient to attend treatment about 2-3 times a week for about 2 to 3 months. Side effects include skin aging, sunburn and increased incidence of skin cancers.

Oral systemic agents such as methotrexate, acitretin and cyclosporin are effective in controlling the disease but have side effects which include liver and kidney toxicity and are also usually reserved for patients with moderate to severe psoriasis.

Dr Colin Theng is currently a Consultant Dermatologist at the National Skin Centre. He is the Chief of the Psoriasis and Phototherapy Unit at the National SkinCentre. His subspecialty interests include psoriasis, photobiology and phototherapy. He is currently President of the Psoriasis Association of Singapore, a position he has held since 2005.