Psoriasis refers to a chronic inflammatory skin condition characterised by well-defined, red, and scaly plaques.

Psoriasis affects about 2-4% of the general population regardless of gender. It can start at any age with peaks of onset between ages 15-25 and 50-60. It lasts a lifetime but fluctuates in severity and extent during different time periods. About 1/3 of patients diagnosed with psoriasis have a family history of this skin condition.

Psoriasis is classified as an immune-mediated inflammatory disease (IMID).  It is multifactorial, however, genetics play a very important role. According to the genome-wide association studies report, the histocompatibility complex HLA-C*06:02 (previously known as HLA-Cw6) is associated with early-onset psoriasis and guttate psoriasis. HLA-C*06:02 is not associated with arthritis, late-onset psoriasis, and nail dystrophy .

Immune factors and inflammatory cytokines (messenger proteins) like IL1β and TNFα are responsible for giving psoriasis its clinical features. Current theories are looking at exploring the pathway of TH17 and the release of the cytokine IL17A. 

Psoriasis usually presents with red and scaly plaques with well-defined edges and symmetric distribution across the affected area.  The scale usually has silvery white color, but in the skin folds it appears shiny with a moist-peeling surface. Scalp, elbows, and knees are the most common sites, but any part of the skin can be affected. If treatment is not administrated, the plaques would become very persistent.

Most patients report experiencing a mild itch; however, some have it more severe which leads to excessive scratching and lichenification. As a result, the skin becomes thickened and leathery with an increased count of skin markings. Painful skin cracks and/or fissures can also occur.

When psoriatic plaques clear up, they may leave pale or brown marks which are expected to fade within several months.

There are some key features that are used as helpful cues in determining appropriate investigations and treatment methods. It is possible that overlap may occur. The first feature is the early age of onset (<35) versus the late age of onset (>50). The early age of onset is observed in 75% of all reported cases. The second feature is acute (e.g. guttate psoriasis) versus chronic plaque psoriasis. The third feature is localised (e.g. only the scalp area is affected), palmoplantar psoriasis versus generalised psoriasis. The fourth feature is small plaques, <3cm, versus larger plaques, >3cm. The fifth feature is thin plaques versus thick plaques. The last feature is the involvement of nails or no involvement at all. 

Injuries (e.g., cuts, sunburn, and abrasions), dry skin, obesity, smoking, heavy alcohol consumption, medications (e.g. beta-blockers and lithium), discontinuing oral steroids or strong topical corticosteroids, stressful events, metabolic syndrome( e.g. obesity, type 2 diabetes, hypertension, hyperlipidaemia) are all of the potential risk factors that can trigger the psoriatic onset. 

The medical assessment of psoriasis involves a careful examination and collection of the patient’s history about the effect of psoriasis on their daily life activities as well as evaluation of comorbid factors.

Mild psoriasis is usually treated with prescribed topical agents alone. The selected treatment method may depend on the affected body site, extent, and severity of psoriasis.

Moderate to severe psoriasis is treated with systematic agents (e.g. Methotrexate) in combination with phototherapy.

Centre for Medical and Surgical Dermatology offers different treatment methods for psoriasis that are unique to each patient. For more information on psoriasis, visit the following link: