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Author: Vanessa Ngan, Staff Writer (2014); Updated by Dr Deeva Vather, Paediatric Registrar, Auckland, New Zealand. Editor in Chief: Adjunct A/Prof. Amanda Oakley, Dermatologist, Hamilton, New Zealand, January 2020.
This document incorporates and summarises information from a number of publications, including guidelines published by the National Institute for Health and Care Excellence (NICE) [1,4], UpToDate [2,7,10,16,17,23,26] and the NZ Formulary [20,22]. It is relevant to the treatment of psoriasis in New Zealand.
In this guideline, psoriasis refers to chronic plaque psoriasis, unless otherwise specified.
Psoriasis is a chronic inflammatory skin disorder that is characterised by disfiguring, scaling and erythematous plaques that may be itchy or painful. Although once thought of as a benign dermatological condition with few serious complications, psoriasis is now considered a multisystem inflammatory disease that is associated with, or increases, the risk of other comorbidities. Psoriasis can be both emotionally and physically debilitating and significantly impact the quality of life [1,2].
The prevalence of psoriasis worldwide is 0.5% to 11.4% in adults, and 0% to 1.4% in children .
Psoriasis is a complex immune-mediated disease. T lymphocytes, dendritic cells, cytokines and tumour necrosis factor are key in the pathogenesis .
The clinical features of typical patterns of psoriasis are described below.
Chronic plaque psoriasis is the most common type of psoriasis in children and adults, accounting for 55–90% of cases [2,4]. The scalp, extensor elbows, knees and gluteal cleft are the most frequently involved sites. Plaques are erythematous with defined margins and often have a silvery scale. Scale is less evident after bathing or after the application of a moisturiser. The plaques are frequently pruritic. In people with darker skin, hyperpigmentation may be present .
Guttate psoriasis is characterised by an acute eruption of psoriatic plaques and papules, typically less than 1 cm in diameter. The main sites involved are the trunk and proximal extremities. Guttate psoriasis is strongly associated with a preceding infection, most frequently streptococcal pharyngitis. Typically, it arises in children and young adults who have not had psoriasis before .
Pustular psoriasis has the potential to be life-threatening. It is characterised by rapid-onset generalised erythema, scaling and superficial pustules .
Erythrodermic psoriasis is uncommon, can be acute or chronic, and involves erythema and scaling from head to toe .
Inverse psoriasis is characterised by psoriasis affecting the intertriginous regions, including the axillary, inframammary, inguinal, perineal, genital and intergluteal areas. This type of psoriasis can easily be misdiagnosed, as there is often no visible scale. It affects children more commonly than adults [2,7].
Signs of nail matrix disease include pitting, leukonychia, red spots on the lunula and crumbling of the nail plate. Signs of nail bed involvement include the oil drop sign, onycholysis, subungual hyperkeratosis and splinter haemorrhages .
Koebnerised psoriasis is psoriasis arising in areas of cutaneous injury [8,9].
Approximately 7–42% of people with psoriasis develop psoriatic arthritis .
Comorbidities associated with psoriasis include obesity, metabolic syndrome, cardiovascular disease, malignancy, autoimmune disease (eg, inflammatory bowel disease, coeliac disease and diabetes), chronic kidney disease, non-alcoholic fatty liver disease (NAFLD), depression, and alcohol abuse [8,10].
Severe psoriasis can cause death, particularly extensive erythrodermic and pustular psoriasis .
Psoriasis is a clinical diagnosis. A skin biopsy can be considered when there is diagnostic uncertainty .
Psoriasis is assessed by evaluating:
An objective assessment of psoriasis severity can be made using the static Physician’s Global Assessment (see below) or the Psoriasis Area and Severity Index (PASI). The PASI is generally used in specialist settings .
0 - no plaque elevation above the normal skin
0 - no evidence of erythema, hyperpigmentation may be present
0 - no evidence of scale
|Average score||0 = clear, 1 = nearly clear, 2 = mild, 3 = moderate, 4 = severe and 5 = very severe|
The patient's assessment of the severity of their psoriasis can be assessed using the static Patient's Global Assessment (graded as clear, nearly clear, mild, moderate, severe or very severe)  or a validated self-assessed or patient-oriented PASI score.
Body surface area (BSA) affected can be classified as:
(Note: 0.5% of BSA in adults is approximately equal to the palm of the patient’s hand, excluding fingers )
The following features may indicate severe psoriasis due to the impact on the quality of life:
When assessing the impact of psoriasis on physical, psychological and social wellbeing, questions to consider include:
Quality of life measurement is important to properly assess the full effect of an illness such as psoriasis on patients. Two dermatology specific tools to assess the impact on the quality of life are:
People with psoriasis should be screened for psoriatic arthritis annually. This is best achieved in primary care and specialist settings through the use of a validated tool, such as the Psoriasis Epidemiology Screening Tool (PEST) . Consider a non-urgent rheumatology referral or seeking rheumatology advice if the score is > 2 [1,8].
|Have you ever had a swollen joint (or joints)?||1||0|
|Has a doctor ever told you that you have arthritis?||1||0|
|Do your fingernails or toenails have holes or pits?||1||0|
|Have you had pain in your heel?||1||0|
|Have you had a finger or toe that was completely swollen and painful for no apparent reason?||1||0|
|Consider referral to rheumatology with a score > 2|
Assess risk factors and comorbid disease of psoriasis at presentation and as indicated thereafter.
Children with psoriasis may have higher rates of associated comorbid disease. Recommended screening for risk factors and comorbid disease depend on the child’s age .
Eye conditions may occur more commonly in people with psoriasis (blepharitis, conjunctivitis, xerosis, corneal lesions and uveitis). Consider asking patients about ocular symptoms at each follow-up appointment .
Similarities to psoriasis — seborrhoeic dermatitis presents with erythematous patches with overlying scale. The scalp, ears and intertriginous areas are commonly affected.
Differences from psoriasis — seborrhoeic dermatitis has a fine, greasy scale. The eyebrows, nasolabial folds, central chest and postauricular area are generally involved .
Similarities to psoriasis — atopic dermatitis commonly presents as excoriated areas with erythema, hyperpigmentation and scale. Lichenification may be present.
Differences from psoriasis — atopic dermatitis generally lacks the thick, coarse-scale and well-demarcated borders of psoriasis. Itch is a more prominent feature of atopic dermatitis, and in infants, the napkin area is usually spared.
Occasionally patients are affected by both atopic dermatitis and psoriasis [2,7].
Similarities to psoriasis — fungal infections present with erythematous plaques and pustules. Onychomycosis may be mistaken for nail psoriasis.
Differences from psoriasis — a skin scraping or nail clipping show fungal elements on microscopy and the causative organism is confirmed by culture .
Similarities to psoriasis — cutaneous T-cell lymphoma usually presents with erythematous, scaly plaques and variable itch, and sometimes as erythroderma (Sézary syndrome).
Differences from psoriasis — the plaques of cutaneous T-cell lymphoma tend to be less circumscribed and less scaly, and they are not distributed symmetrically.
Lymphadenopathy and hepatosplenomegaly are common in cutaneous T-cell lymphoma [8,16].
The differential diagnosis of chronic plaque psoriasis also includes:
Pityriasis rosea is an important differential for guttate psoriasis .
While psoriasis is treatable, there is no cure . Successful management is dependent on the patient understanding the chronic nature of psoriasis and the therapeutic options that are available to them. Points to consider include:
An acceptable treatment response is either BSA ≤ 3% or an improvement in BSA ≥ 75% from baseline, 3 months after treatment initiation .
The ideal target for treatment response is BSA ≤ 1% 3 months after treatment initiation maintained at every 6-month assessment interval during maintenance therapy.
Referral to a dermatologist for advice or face-to-face assessment is recommended in the following circumstances:
Note: Public hospital dermatology services in NZ may have more stringent referral criteria due to a dermatology workforce shortage.
Consider patient preferences, cosmetic and practical aspects of treatment, and the body surface area affected .
Tacrolimus and pimecrolimus
Flow charts for topical therapy
Download flow charts as PDF files:
Phototherapy appears to slow keratinisation and reduce the activity of T cells implicated in the formation of psoriatic plaques .
The following are indications for systemic treatment:
Systemic therapy should be initiated in a specialist setting. Monitoring and supervision can occur in non-specialist settings when these arrangements have been formalised and agreed upon .
The NICE guidelines suggest systemic non-biologic therapy should be offered to people with any type of psoriasis if :
Non-biologic systemic therapy outcomes can be optimised with the use of adjunctive topical therapy .
All patients using non-biologic systemic therapy need close monitoring for adverse effects, as per local protocols [20,22,24].
Non-biologic systemic agents include methotrexate, ciclosporin, acitretin and apremilast.
Biologic agents are effective in treating moderate to severe chronic plaque psoriasis. Studies show excellent short and long term results, and treatment is generally well tolerated . While they are often more efficacious than non-biologic systemic therapies, the long term risks are still largely unknown. In addition, biologic systemic therapy is expensive, hence their use in clinical practice remains limited.
In New Zealand, a special authority application is required for a subsidy of biologic treatments [20,22].
Psoriasis often has an unpredictable clinical course. Plaque psoriasis is generally a chronic disease, with fluctuating severity over time. Guttate psoriasis may resolve, relapse or develop into chronic plaque psoriasis. Generalised pustular psoriasis frequently has a variable and protracted course without intervention .
As mentioned above, psoriasis is now recognised as a multisystem inflammatory disease. People with psoriasis have an increased risk of mortality compared to those unaffected by psoriasis [2,31]. Specifically, studies suggest an increased liver, kidney, infectious disease and chronic lower respiratory disease mortality risk. Patients with severe psoriasis also appear to have higher cardiovascular disease and neoplasm mortality risk . The cause of the increased mortality risk is unknown. Postulated contributing factors include systemic inflammation, adverse effects of systemic treatments, comorbid conditions and behavioural risk factors [2,31]. Screening and holistic care may help minimise these risks.
If you are not based in New Zealand, we suggest you refer to your national drug approval agency for further information about medicines (eg, the Australian Therapeutic Goods Administration and the US Food and Drug Administration) or a national or state-approved formulary (eg, the New Zealand Formulary and New Zealand Formulary for Children and the British National Formulary and British National Formulary for Children).
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