1.1. Epidemiology

The prevalence of psoriasis is estimated to be around 1.3–2.2%³⁰⁶ in the UK, with the greatest prevalence being in white people. Men and women are equally affected. It can occur at any age although is uncommon in children (0.71%) and the majority of cases occur before the age of 35 years. Psoriasis is associated with joint disease in a significant proportion of patients (reported in one study at 13.8%)¹⁵⁷.

1.2. Clinical features

Plaque psoriasis is by far the most common form of the condition (90% of people with psoriasis) and is characterised by well delineated red, scaly plaques³⁰⁶. The extent of involvement is variable, ranging from a few localised patches at extensor sites, to generalised involvement involving any site. Rarely, psoriasis may involve the whole body, erythroderma. The appearance of plaque psoriasis may be modified by site. Flexural (also known as inverse or intertriginous) psoriasis refers to plaque psoriasis at submammary, groin, axillary, genital and natal cleft sites, and is typically less scaly. Seborrhoeic psoriasis (‘sebopsoriasis’) is similar in appearance and distribution to seborrhoeic dermatitis (hence the name) and may occur in isolation or associated with plaque psoriasis elsewhere. Other types of psoriasis include guttate psoriasis (an acute eruption of small (< 1 cm) papules of psoriasis which appear over a period of a month or so and is preceded by a streptococcal infection in around 2/3rd of people), and pustular psoriasis which includes generalised pustular psoriasis (GPP) and localised forms (ie: palmoplantar pustulosis and acrodermatitis continua of Halopeau). Distinctive nail changes occur in around 50% of all those affected and are more common in those with psoriatic arthritis. Occasionally combinations of the different types develop simultaneously or sequentially over time in the same person. Plaque psoriasis is usually the type referred to by both healthcare professionals and patients when using the term ‘psoriasis’³⁷⁵. Unless stipulated otherwise, the term psoriasis refers to plaque psoriasis in this guideline. The phrase ‘difficult-to-treat sites’ encompasses the face, flexures, genitalia, scalp, palms and soles and are socalled because psoriasis at these sites may have an especially high impact, may result in functional impairment, require particular care when prescribing topical therapy and can be resistant to treatment.

1.3. Disease impact

Death directly due to psoriasis is rare, but the chronic, incurable nature of psoriasis means that associated morbidity is significant. People with psoriasis, like those with other major medical disorders, have reduced levels of employment and income as well as a decreased quality of life. The impact of psoriasis encompasses functional, psychological, and social dimensions²⁰⁵. Factors that contribute to this include symptoms specifically related to the skin (for example, chronic itch, bleeding, scaling and nail involvement), problems related to treatments (mess, odour, inconvenience and time), psoriatic arthritis, and the effect of living with a highly visible, disfiguring skin disease (difficulties with relationships, difficulties with securing employment and poor self esteem). Even people with minimal involvement (less than the equivalent of three palm areas) state that psoriasis has a major effect on their life. The combined costs of long-term therapy and social costs of the disease have a major impact on healthcare systems and on society in general. About a third of people with psoriasis experience major psychological distress, and the extent to which they feel socially stigmatised and excluded is substantial³³². Healthcare professionals, including dermatologists, often fail to appreciate the extent of this disability and even when it is correctly identified, some estimates suggest that less than a third of people with psoriasis receive appropriate psychological interventions.

1.4. Comorbidities

Aside from the burden of psoriatic arthritis, and psychological morbidity, a number of studies have suggested that people with psoriasis may also be at risk of cardiovascular disease. It is unclear whether this increase directly relates to the psoriasis itself, or an increased incidence of traditional cardiovascular risk factors reported in people with psoriasis^180,322. Risk factors include obesity, type 2 diabetes mellitus, metabolic syndrome, excess alcohol intake or alcoholism, smoking and hyperlipidaemia (which may be partly iatrogenic due to agents such as ciclosporin and acitretin). Community- and hospital-based studies suggest that people with psoriasis, particularly those with severe disease, may also be at increased risk of lymphoma and non-melanoma skin cancer. The relative influence of known confounders such as concomitant therapy with immunosuppressants, phototherapy, smoking, and alcohol is unclear.

1.5. Approach to Management

The significant impact of psoriasis on wellbeing suffered by affected individuals, underlines the need for prompt, effective treatment, and long-term disease control. Treatments available for psoriasis are varied. For the purposes of this guideline, first-line therapy describes the traditional topical therapies (such as corticosteroids, vitamin D and analogues, dithranol and tar preparations). Second-line therapy includes phototherapy, broad- or narrow-band ultraviolet [UV] B light, with or without supervised application of complex topical therapies such as dithranol in Lassar’s paste or crude coal tar and photochemotherapy, psoralen plus UVA light [PUVA], and non-biological systemic agents such as ciclosporin, methotrexate and acitretin. Third-line therapy refers to systemic biological therapies that use molecules designed to block specific molecular steps important in the development of psoriasis such as the TNF antagonists adalimumab, etanercept and infliximab, and ustekinumab, anti-IL12-23 monoclonal antibody^{266,267,269,273}. These agents are approved for use by NICE, subject to certain disease severity criteria, and acquisition costs are high. All of these interventions can be associated with long-term toxicity and some people with psoriasis have treatment-resistant disease. In common with many long term conditions, poor adherence to prescribed treatment can prevent optimal outcomes, and is influenced by multiple factors including those related to the treatment itself (for example complex, cosmetically unacceptable topical regimens), quality of communication between clinician and patient, as well as beliefs and perceptions of the individual affected.

The approach to therapy is, to a large degree, governed by the extent and severity of disease. In general, people whose disease is localised to <3% body surface area or 3 palms worth, which comprises the vast majority of people affected with psoriasis²⁰⁴, can be managed with topical therapy alone. Attention to cosmetic acceptability, formulation, local side effect profiles, and practicalities of application are important to achieve optimal outcomes with topical therapies. In people with psoriasis that is extensive, where topical therapy would be impractical or ineffective or that is associated with psoriatic arthritis, second line therapies tend to be used. Recent guidelines from the British Association of Dermatologists (which are in line with NICE guidance and the UK marketing authorisation for these drugs)³⁷⁴ recommend that third-line biological therapies should be generally reserved for people with severe disease for whom second line treatments have failed or cannot be used. There are important exceptions to this general over view however, as even localised disease can be resistant to treatment and may have a very significant impact on patients’ functional, psychological or social wellbeing, such that escalation to second line or even third line therapy is appropriate. Equally, some people with extensive disease, will only seek advice and be interested in treatments for localised sites that are especially bothersome, for example, visible sites such as the face or backs of hands. Setting aside psoriatic arthritis, there is no compelling evidence that any of the interventions have a disease modifying effect or impact beyond improvement of the psoriasis itself and so, with the exception of the minority of patients with unstable and life threatening forms of psoriasis, the approach to therapy and risk/benefit assessment of the different interventions is strongly influenced by the impact the psoriasis is having on the wellbeing of the individual affected.

1.6. Service configuration and pathways of care

Most people with psoriasis are managed in primary care⁴⁵; one study found that specialist referral is required in up to 60% at some point in their disease course^277,355. These data are based on adult populations, but approach to care in children and young adults is similar. Commonly cited triggers for referral for specialist opinion include: diagnostic uncertainty; request for further counselling or education including demonstration of topical treatment; failure to respond to appropriately used topical therapy for three months; psoriasis at sites that are difficult to treat and/or at high impact sites; if unresponsive to initial therapy; adverse reactions to topical therapies; need for systemic therapy, phototherapy, day treatment, or inpatient admission; disability preventing work or excessive time off work; significant psychosocial disability; presence of psoriatic arthritis and; life threatening forms of psoriasis where urgent referral may be justified.

Ongoing supervision of those on systemic therapy occurs in specialist settings, sometimes with shared care arrangements for drug monitoring in primary care. Supra-specialist (level 4, tertiary) centres with access to multidisciplinary teams with experience in complex interventions and associated multi-morbidities provide specialist care for the minority of people. A recent UK audit in the adult population demonstrated wide variations in practice, and in particular, access to specialist treatments (including biologics), appropriate drug monitoring, specialist nurse support and psychological services⁸². No comparable audit has been carried out in children. Recommended indications for referral from primary to specialist care have been published⁴⁶ but there are no formal standards/indications for supra-specialist level care (level 4).

Delivery of care in all specialist (level 3 and 4) settings⁴⁵ largely follows the traditional model of outpatient consultations with daycare/inpatient admission for more severe disease. People on biological therapy attend secondary or tertiary care centres for monitoring whilst the drug itself is delivered by community based companies.

Good communication between healthcare professionals and patients is essential. It should be supported by evidence-based written information tailored to the patient’s needs. Treatment and care, and the information patients are given about it, should be accessible to people with additional needs and culturally appropriate. Families and carers should also be given the information and support they need.

1.7. Psoriasis in children and young people

Psoriasis in childhood is less common than adults. It tends to present in later childhood with a median age of onset between 7 and 10 years and an estimated UK prevalence of 0.71%^{91,203,260,363}. Since one third of adult patients with psoriasis present before 20 years of age they are an important group to consider in the overall disease management²⁰. A positive family history of psoriasis is associated with a reduced age of onset of the disease^16,145.

Paediatric practice tends to mirror that in adults, and in this guideline, recommendations relate to everyone with psoriasis irrespective of age, unless otherwise stated. The term ‘children’ refers to those up to 12 years, who become ‘young people’ thereafter, before merging with the adult population by 18 years of age. Within the recommendation, the term ‘people’ is used to encompass all ages. Adult and paediatric healthcare teams should work jointly to provide assessment and services to young people with psoriasis. Diagnosis and management should be reviewed throughout the transition process, and there should be clarity about who is the lead clinician to ensure continuity of care.

Points of particular relevance to the paediatric population include the following:

• Plaque type psoriasis is also the most common form in the paediatric population. Other forms are guttate psoriasis with relapses following infections³²⁶ and in very young children, less than two years of age, napkin psoriasis. This typically affects the inguinal folds and then spreads to involve the trunk and limbs⁶².
• As with any condition occurring in children and young people, psoriasis may impact on the person’s psychological and emotional development and educational needs. During adolescence, the impact of psoriasis can be especially challenging when issues around body image and appearance are particularly salient. All these aspects need to be considered in context of the individual, family and carers, and appropriate support provided. There is a lack of data on interventions in children and young people with psoriasis. The GDG agreed to base treatment recommendations on RCTs with extrapolation to children if no separate paediatric evidence was found. Any exceptions to this principle are noted in the LETR tables of the relevant review questions. Note that only two studies^62,295 that specifically addressed psoriasis in children were identified and included in the guideline.
• Psoriasis in children and young people is currently managed as part of the general paediatric dermatology case mix by consultant dermatologists who also care for children. There are no specialised paediatric psoriasis clinics although combined paediatric dermatology and rheumatology clinics are in existence in some centres to manage psoriasis and psoriatic arthritis in children. Due to the drug licensing restrictions, children with relatively mild disease are often referred to secondary care for treatment.
• Most topical agents have licensing restrictions from specific ages and systemic therapies are currently not licensed for the treatment of psoriasis in children of less than 16 years of age apart from Etanercept (the only biological therapy currently licensed for children of less than 16 years of age). Ultimately the prescriber must take responsibility for using drugs outside of their licensed indications but it is important to involve the parents and, if possible the child, in a discussion about risks and potential benefits, especially when considering interventions such as PUVA and systemic drugs. In all discussions with patients about their treatment the clinician should establish that the patient has the capacity² to make a fully informed decision about their care, and the ability to understand the potential benefits (and risks) of treatment.
• In the case of children, clinicians would normally involve those with parental responsibility in the clinical decision-making process. Clinicians should also consider the maturity and competence of the child to understand and make decisions about their own care. Children can consent to treatment when they are able to understand the risks and benefits but they cannot legally refuse treatment against their parents’ wishes until they are 16 years old. It is important to consider the young person’s cognitive developmental stage when discussing the disease and treatment options. Using appropriate terminology will help children and young people participate actively in decision-making.
• As children mature into young people and adults they should be encouraged to take more responsibility for managing their condition. Arrangements for transition to adult care (e.g. joint clinics with adult and paediatric dermatology teams) should be an integral part of the service. The relevant principles are considered in a Department of Health publication⁷⁵.
• When managing psoriasis in children and young people, treatment choice should be carefully considered to avoid or minimise long-term sequelae. This aspect is especially pertinent in relation to phototherapy.

1.8. Aims of the Guideline

Psoriasis is a common, chronic disease, which for many people, is associated with profound functional, psychological and social morbidity and important comorbidities. Effective treatments are available. Some treatments are expensive; all require appropriate monitoring and some may only be accessed in specialist care settings. Evidence indicates that a substantial proportion of people with psoriasis are currently dissatisfied with their treatment.

This guideline aims to provide clear recommendations on the assessment and management of psoriasis for all people with psoriasis. The diagnosis of psoriasis has not been included within the scope, partly for pragmatic reasons given that to cover psoriasis management itself is a considerable task, but also because there are no agreed diagnostic criteria or tests available and accurate diagnosis remains primarily a clinical one. In considering which specific aspects of psoriasis management to address, the guideline development group have focussed on areas most likely to improve the management and delivery of care for a majority of people affected, where practice is very varied and/or where clear consensus or guidelines on treatments are lacking. We have therefore addressed how to holistically assess people with psoriasis at all stages in the treatment pathway, the use of first, second and third line interventions and when to escalate therapy, and the role of psychological interventions and self-management strategies. We have avoided categorical description of what constitutes particular levels of disease severity, for example ‘mild’ or ‘moderate and severe’ excepting disease severity criteria for plaque psoriasis already described by NICE in order to qualify for biological therapy. There are no widely accepted definitions that are applicable to all situations and it is a contentious subject. Instead we emphasise the importance of measuring disease severity and impact to individualise care, and plan and evaluate management. There are also a number of key areas that we have not addressed for a variety of reasons. First, we have not evaluated the role of emollients in the treatment of psoriasis. These are widely prescribed and clinical experience suggests that they are used with benefit by patients. In the absence of robust RCT or high quality studies to inform recommendations to change this practice, and the fact that all placebo controlled trials involving topicals use a vehicle (which will have emollient properties) in the placebo arm, the treatment pathway starts on the assumption that when appropriate, emollients have already been prescribed. Secondly, we have not included fumaric acid esters in our evaluation of second line therapies. This intervention is not licensed for any indication in the UK and therefore cannot be included.

We sincerely hope that these guidelines facilitate the delivery of high-quality healthcare and improve outcomes for people with psoriasis.