Last updated: December 2023
What is psoriasis?
Psoriasis is a lifelong skin condition characterised by the development of red scaly areas of skin. It is not contagious.
About 50% of people affected with psoriasis have changes to their nails and about 25% of people have pain, swelling and tenderness of their joints.1
Who gets psoriasis?
Psoriasis can develop at any age. The condition usually starts in young adults in their early 30s, with 75% of affected people developing psoriasis before the age of 45 years.
What causes psoriasis?
The exact cause of psoriasis is unknown. It is thought that psoriasis develops in individuals who have an inherited tendency for the immune system in their skin to react abnormally to certain environmental conditions.
Psoriasis is more common in individuals who have relatives with psoriasis.
Psoriasis may also be triggered for the first time by infections such as streptococcal tonsillitis, HIV and other viral infections, as well as by severe emotional stress.
Smoking and excessive alcohol intake may worsen the condition.
Some medications may trigger psoriasis or cause psoriasis to become more severe. These medications include lithium, beta-blockers, anti-malarial medication, and rapid withdrawal of systemic corticosteroids.
What does psoriasis look like?
There are many different types of psoriasis.
- Plaque psoriasis occurs in 90% of people affected by psoriasis.1 It is often characterized by thick, sharply edged (marginated), red, scaly lesions. Plaque psoriasis may be seen on any area of the skin, but the elbows, knees, lower back and scalp are most commonly affected by the condition.
Less common forms of psoriasis include:
- Inverse (flexural) psoriasis occurs in the armpits, groin, between the buttocks, in the belly button (umbilicus), the ears and other areas where skin rubs against skin. It is often characterized by sharp-edged patches with little or no scale.
- Palmoplantar psoriasis occurs on the palms of the hands or soles of the feet. It is often characterized by scaling, redness or pustules (small blister or pimple on the skin containing pus).
- Guttate psoriasis is commonly seen in young adults 2-3 weeks after they have had tonsillitis or a viral infection. It develops rapidly and is often characterized by widespread, small, thin, teardrop lesions. It usually improves over a period of 2-3 months.
- Pustular psoriasis is a very rare form of psoriasis which appears suddenly and presents as small pustules developing in inflamed skin and spreading rapidly.
- Erythrodermic psoriasis is a rare form of psoriasis which can be serious. Red, inflamed areas of psoriasis spread to involve all of the skin. These individuals have usually had a history of stable plaque psoriasis in the past that changes into the widespread erythrodermic variant. Possible triggers of erythrodermic psoriasis may include irritating agents applied to the psoriasis, quick withdrawal of corticosteroids, certain medications or severe emotional stress. Oral medications may be used to control the condition.
How is psoriasis diagnosed?
Psoriasis is usually diagnosed clinically. A biopsy may be needed to distinguish psoriasis from other skin conditions that cause redness and scaling of the skin.
How is psoriasis treated?
Treatment options will vary depending on the individual and their needs. The aim of the treatment is to clear the lesions and control symptoms.
General measures include:
- Daily application of moisturiser to the skin to maintain skin hydration and barrier function.
- Smoking cessation
- Avoiding excessive alcohol intake
- Maintaining optimal weight
Specific treatment may include:
- Topical treatments, such as corticosteroids, Vitamin D analogues, tazarotene, coal tar and dithranol
- Ultraviolet (UV) phototherapy and photochemotherapy, such as narrowband UVB and PUVA.
- Systemic treatments, such as methotrexate, cyclosporin, retinoids, apremilast, deucravacitinib, and biologic agents.
What is the likely outcome of psoriasis?
Psoriasis is a chronic condition. It tends to flare up and down over time. Lifelong treatment and intervention may be needed to keep the skin clear of psoriasis or treat joint disease.