Psoriasis | Mate tongatonga uri

Psoriasis is a chronic inflammatory skin condition. The skin symptoms of psoriasis are due to abnormally fast cell growth. In normal skin, cells mature in 28 to 30 days. In psoriasis, skin cells are made 10 times faster. This means they don't have enough time to mature. The immature cells stick together, creating the thick scales seen in psoriasis. Patches of psoriasis appear in cycles which may last for weeks or months. 

Psoriasis isn't contagious, so it can't be caught from someone else.

Psoriasis is an autoimmune mediated genetic skin disease. The potential to get psoriasis is in the genes you inherit from your parents. The inheritance is multifactorial, which means there is more than just 1 gene involved. About 1 in 3 people with psoriasis has a family member who has it too.

The skin changes often start between the ages of 15 and 25 or, less commonly, between the ages of 50 and 60. It’s more common in Caucasians. The symptoms usually start for the first time, or existing psoriasis can worsen, after a trigger.

An environmental factor, such as getting a strep throat, triggers your immune system to mistakenly target your skin cells – this is the autoimmune part. A type of white blood cells (called T-cells) mistakenly makes natural chemicals called cytokines, which make your skin cells grow too fast and stick together.

Triggers for psoriasis can include:

• skin injuries, including severe sunburn
• streptococcal tonsillitis or another infection
• a stressful event
• medicines, eg, lithium, beta-blockers, non-steroidal anti-inflammatories (NSAIDs), terbinafine, antimalarials, immunotherapy
• alcohol
• smoking
• hormonal changes – puberty and menopause are common times for flare-ups in women
• stopping oral steroid medicine, eg prednisone tablets. 

Psoriasis usually looks like a patch of dry, red flaky skin. Each patch is called a plaque. 

A psoriasis plaque:

• has a clear edge
• is covered with silvery white scale, unless it's in a fold of skin such as between your buttocks – then it looks shiny and moist and can have peeling skin on top
• looks less red if your skin is darker, and can be thicker, more scaly and look purple or brown
• is most common on your scalp (which might be the only place you have it) your elbows, knees or lower back – but can be anywhere
• can be any size
• isn't usually too itchy but can be very itchy and your skin can become thick and leathery from scratching
• doesn't usually hurt, but if the skin cracks it can be painful – especially if it's on the palms of your hands or soles of your feet
• can appear on an old scar (the Koebner phenomenon)
• sticks around for weeks or months unless it's treated
• can flare up suddenly
• can leave behind a darker or lighter patch of skin after it clears up, which fades over a few months. 

There are many types of psoriasis which can look different and appear in different places on your body. You can have only 1 type or a combination of different types of psoriasis.

• Chronic plaque psoriasis – this is the most common type making up about 90% of all psoriasis. It’s usually on your elbows, knees, scalp and lower back. The plaques are more than 3 cm wide.
• Guttate psoriasis – this is often described as a ‘raindrop’ pattern of small plaques less than 1 cm wide, and is most common following a sore throat. It's usually seen in children.
• Flexural psoriasis (inverse psoriasis) – this looks smooth and shiny and is found in skin folds and on your genitals. Candida yeast often grows in these plaques.
• Sebopsoriasis – an overlap of seborrhoeic dermatitis(external link) and psoriasis, on your scalp, face ears and chest. Malassezia yeast may grow in this type of psoriasis.
• Palmoplantar psoriasis – on your palms and the soles of your feet, often with very thickened, cracked skin.
• Nail psoriasis – this type commonly affects your fingernails, causing pitting, yellowing and ridging of your fingernails. People with nail psoriasis are more likely to have psoriatic arthritis (arthropathy).
• Pustular psoriasis – this type has a pattern of pus-filled spots (pustules). It can affect your palms and soles or all your body.
• Erythrodermic psoriasis – this rare type causes a widespread painful redness of your skin and a high fever. It needs urgent treatment in hospital.
  
  
  

The image below shows 2 different types of psoriasis. 

Image credit: DermNet NZ

See your GP or nurse practitioner for a diagnosis. They will ask you questions about your family history and your symptoms and will have a look at your skin. You may also need to have a skin sample (biopsy) taken to confirm your diagnosis.

Your healthcare provider may use the Psoriasis Area Severity Index calculator(external link) to work out how severe your psoriasis is. They may also ask you to fill in a questionnaire, the Dermatology quality of life index (DQLI)(external link), which has 10 questions about how psoriasis impairs (affects) your quality of life. It produces a score from 0 (not impaired) to 30 (severe impairment).

Your healthcare provider may refer you to a dermatologist (doctor specialising in diagnosing and treating skin conditions) if:

• they're uncertain about the diagnosis of psoriasis
• your psoriasis covers more than 10% of your skin – you can measure this with the palm of your hand which is about the size of 1% of your skin
• you're having an acute flare of pustular or erythrodermic psoriasis
• your psoriasis is in challenging places such as your genitals, hands or feet
• topical treatments (eg, ointments or creams put onto your skin) haven't worked well.

To help control your psoriasis and prevent flare-ups, you need to look after yourself and your skin. Research shows that better general health is associated with less severe psoriasis and fewer flare-ups. 

• Have warm baths with a bath oil or tar solution to soften your psoriasis and lift the scale.
• Use moisturisers as soap substitutes and avoid antiseptics and harsh soaps. Read more about how to use emulsifying ointment in place of soap.
• Use emollients or moisturisers to keep psoriasis soft and prevent it from cracking and becoming sore.
• Cover small patches of psoriasis with waterproof adhesive dressings. If you haven't used this type of dressing before, attach it to the inside of 1 forearm, leave it for 30 minutes, then check for any reaction (some people are allergic to the adhesive).
• Get sunshine in small doses to help clear psoriasis. Take care to avoid sunburn by using SPF 50+ sunscreen, as sunburn can cause flare-ups and lead to skin cancer. A few people find sunshine makes their psoriasis worse. If that's the case for you, you'll need to cover up and stay in the shade. Don't use a sunbed – they don't work for psoriasis because they have the wrong frequency of UV light, and you risk getting skin cancer.
• If you smoke, get support to quit, as smoking may make your symptoms worse.
• Avoid drinking too much alcohol as this can also make your symptoms worse. Read more about recommended alcohol limits.
• Reduce stress and learn how to manage it.
• Don't put pressure on the affected skin, eg, if you have psoriasis on your knees, avoid kneeling.
• Have regular follow-ups with your healthcare provider.
• Use your medicines as prescribed. 
• Exercise regularly.
• Eat a healthy, balanced diet. Talk to your healthcare provider about whether you need a vitamin D supplement. Special diets don't help with psoriasis. 

Apps reviewed by Healthify

You may find it useful to look at some psoriasis and skin care (dermatology) apps.

Psoriasis can't be cured, but it can be controlled with treatment. You can work out a personalised treatment plan with your healthcare provider.

Your plan will take into account your:

• overall health
• age
• lifestyle
• psoriasis severity and the length of time you've had it
• expectations about treatment. 

Various treatments, combinations of treatments and many visits to your healthcare provider may be needed before your psoriasis is controlled. Read more about psoriasis treatment.

Treatments applied to the skin (topical treatments)

These ingredients are often mixed together in a single product. Some topical treatments need a prescription, but many can be bought over-the-counter at your pharmacy or supermarket.

• Emollients and moisturisers, eg, cetomacrogol – these help with dryness and itch, make plaques less thick and help your skin absorb other treatments. They should be used instead of soap when you wash, and also put on your skin every day.
• Coal tar preparations – these help with scale and itch, and are often used on your scalp.
• Salicylic acid – softens the top keratin layer, making it easier to rub off.
• Vitamin D analogs, eg, calcipitriol – stop the abnormal growth of skin cells.
• Topical steroids (eg, hydrocortisone, betamethasone) – stop the abnormal growth of skin cells, narrow widened blood vessels and reduce inflammation.
• Calcineurin inhibitors (eg, pimecrolimus) – damp down your immune system.

Other types of treatment

If your psoriasis isn't well managed with topical treatments, you can be referred to a dermatologist for 1 or more of the following:

Phototherapy

This is light therapy, usually narrow band ultraviolet B light exposure (NB-UVB therapy). It takes about 3 visits each week to a hospital or private dermatology clinic for 5 to 8 weeks. Each light exposure lasts 5 to 20 minutes.

Systemic medicines

These are medicines that work throughout your whole body. They are usually used when psoriasis is widespread or doesn't respond to other treatments. Generally, they're very effective, but they can have potentially serious side effects, as most of them work by suppressing your immune system. For this reason, they need to be used carefully. Non-biological medicines taken by mouth (orally) include cyclosporin, methotrexate, mycophenolate and acitretin. 

Biologic medicines

These are made from living material from humans, plants, animals or microorganisms. Because they act on your immune system, they have risks which need to be carefully talked through. They are only funded in Aotearoa New Zealand if other medicines haven’t worked. They're given by injection. In this group are tumour necrosis factor inhibitors (infliximab, adalimumab and etanercept) which reduce the activity of this cytokine (a protein important in sending messages between cells involved in inflammation and immune responses). 

Monoclonal antibodies (eg, secukinumab and ustekinumab) are used to target interleukins which are another type of cytokine made by white blood cells to regulate immune response. 

Read more about biologic medicines.

Chronic plaque psoriasis usually comes and goes. You may have years between flare-ups. For some people it may eventually go away completely.

Guttate psoriasis usually lasts a few months then goes away completely. However if you’ve ever had an episode of guttate psoriasis you have a higher chance of having chronic plaque psoriasis later in life.

There's no known way of preventing psoriasis but avoiding triggers can help prevent flare-ups.

Health

If you have psoriasis, you're more likely than other people to have some other health problems too:

• About 30% of people with psoriasis will develop psoriatic arthritis. Early morning stiffness is a common sign of this inflammatory joint disease. Other symptoms of psoriatic arthritis include tenderness, pain, discomfort, throbbing or swelling in one or many joints. Read more about psoriatic arthritis.
• Inflammatory bowel disease (IBD).
• Uveitis (a type of eye inflammation).
• Coeliac disease
• Non-alcoholic fatty liver disease (NAFLD)
• Metabolic syndrome – the combination of high blood pressure, being overweight, diabetes and cardiovascular disease.  If this applies to you, then managing these problems well can improve your psoriasis.

Quality of life

Living with a chronic, visible skin disease can have a huge impact on your quality of life. As a result, people with psoriasis are more likely to:

• experience depression
• drink too much alcohol
• smoke
• be unemployed
• avoid social situations.

If psoriasis is affecting your quality of life, talk to your healthcare provider – there's help available. 

Clinical resources and guidelines

Treatment of psoriasis(external link) DermNet NZ, 2023
Chronic plaque psoriasis – an overview of treatment in primary care(external link) BPAC, NZ, 2017
Choosing a topical treatment for patients with chronic plaque psoriasis(external link) BPAC, NZ, 2017
Monitoring patients with moderate to severe psoriasis(external link) BPAC, NZ, 2017
Psoriasis assessment and management(external link) NICE Guidelines, UK, 2017

Continuing professional development

eLearning

Ask an expert – psoriasis(external link) BMJ Learning, UK (requires registration with an annual fee for some users)

Podcast

Psoriasis – Paul Jarrett(external link) Goodfellow Unit, NZ, 2017
Dr Paul Jarrett talks about prescribing tips for psoriasis. Paul is a consultant dermatologist at Counties Manukau DHB and is clinical lead for dermatology, teaching in the department of medicine at The University of Auckland.

Video: Goodfellow Unit MedTalk: Psoriasis

Dr Diana North, Goodfellow GP Advisor talks with Dr Maneka Deo, Specialist Dermatologist, about the management of psoriasis in primary care. 

(Goodfellow Unit, NZ, 2017)