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TapioRantanen

Psoriasis

Essentials

According to a report published by the WHO in 2016, the prevalence of psoriasis in different countries ranges between0.09% and 11.4% http://apps.who.int/iris/bitstream/handle/10665/204417/9789241565189_eng.pdf. It is rare in young children (picture 1).
- There are two peaks of onset, and both have a different genetic background.
  - Early onset psoriasis develops before the age of 40 years, is often familial and, on average, more severe than the late onset type.
- The triggering factor in early onset psoriasis, particularly in guttate psoriasis, is often a streptococcal infection, whereas late onset psoriasis is highly associated with preceding stressful life events.
- Obesity, smoking and excessive alcohol consumption are other known risk factors.
Psoriasis is a chronic, disfiguring and stigmatising disease which may adversely affect the patient's self image and quality of life. It may be associated with significant anxiety and depression.
Psoriasis is associated with e.g. an increased risk of obesity, diabetes and dyslipidaemia as well as hypertension and other cardiovascular diseases. These often go undiagnosed or without adequate treatment.
A considerable share of the patients will over the years develop psoriatic arthritis Psoriatic Arthritis, the early diagnosis and treatment of which may reduce the risk of permanent joint damage.

Clinical features

The diagnosis of psoriasis is based on the clinical picture.
- In special cases, a biopsy specimen Skin Biopsy: Indications and Technique may be beneficial. The specimen should be taken from the middle of an untreated plaque using a 4-6 mm biopsy punch.
Plaque psoriasis (nummular psoriasis, psoriasis vulgaris; picture 2) is the most common type (about 90% of all cases). The characteristic plaques are symptomatic and symmetrically distributed on the elbows (pictures 3 4), knees (picture 5), legs, lower back (picture 6) and scalp (pictures 7 8 9).
- The plaques are sharply demarcated, red and thickened patches with a diameter of no less than 0.5 cm (pictures 10 11). The plaques are covered with a layer of silvery scales, the thickness of which is patient specific and varies according to treatment.
  - Gentle scraping of the scales reveals minute capillary bleeding points (Auspitz sign; picture 12).
  - Plaque psoriasis is further divided into large plaque psoriasis (plaques over 3 cm, picture 2) and small plaque psoriasis (plaques less than 3 cm, picture 13).
- When the plaques are localised within apposed skin surfaces - submammary region, navel (picture 14), groin (pictures 15 16), gluteal cleft (picture 17), axillae (picture 18) - scaling is uncommon (flexural psoriasis, psoriasis inversa).
Guttate psoriasis is a widely distributed skin eruption (picture 19); typically in a young person after streptococcal tonsillitis. The condition usually resolves itself, but it may flare up later with small individual spots or it may develop into plaque psoriasis.
Pustular forms of psoriasis are rare. These include acral psoriasis (pictures 20 21), palmoplantar and generalised psoriasis (picture 22), and erythrodermic psoriasis, which involves the entire skin (pictures 23 24).
The fingernail changes, including pitting (picture 25), oily macules (pictures 26 27), distal onycholysis (picture 28), subungual hyperkeratosis (picture 29) and crumbling of the nail plate, are often useful in differential diagnosis. They are commonly seen in psoriatic arthritis Psoriatic Arthritis.

Differential diagnosis

Scalp

In seborrhoeic dermatitis Seborrhoeic Dermatitis in the Adult (picture 30) the flakes are thinner, "greasier" and the condition responds better to treatment. It is often difficult to differentiate seborrhoeic dermatitis from psoriasis unless other skin areas offer additional information.
Fungal infection of the scalp Dermatomycoses is uncommon in Western populations. It mostly affects children. This diagnosis can be excluded by a negative fungal culture.
Neurodermatitis of the neck (lichen simplex nuchae) 31 is characterised by an isolated, itchy plaque covered with thin scales.

Flexures with apposed skin surfaces

Seborrhoeic dermatitis Seborrhoeic Dermatitis in the Adult (picture 32) may resemble flexural psoriasis. Examine other skin areas. It is not always necessary to differentiate between these two conditions, as the treatment is the same.
Fungal infection (tinea, see Dermatomycoses) in the groin may resemble psoriasis; however, it usually heals in the centre and expands peripherally. Positive fungal culture is diagnostic.
Candidiasis presents as a moist area of erythema with outlying "satellite eruptions". Candidiasis diagnosis may be confirmed with a culture.
Erythrasma is a macular brown area with few symptoms, most often found in the armpit or groin. It is caused by an overgrowth of diphtheroids in the normal skin flora. These areas fluoresce coral pink under long-wave ultraviolet radiation (Wood's light).

Palms, soles of feet

Pictures 33 and 34
It may be difficult to differentiate hyperkeratotic eczema of the palms and palmoplantar pustulosis (pictures 35 36) from psoriasis. Examine the entire skin.
Fungal infection Dermatomycoses is usually unilateral and is easily diagnosed by direct microscopy from a good quality specimen.

Treatment Antistreptococcal Interventions for Guttate and Chronic Plaque Psoriasis, Interventions for Nail Psoriasis

Treatment should aim at minimizing symptoms in the long term and permanently and improving any illness-induced impairment of the patient's quality of life.
Psoriasis may be associated with anxiety or depression as well as other associated diseases requiring further management.
Current treatment practices are listed in table T1. The treatments are divided into topical treatment, phototherapy and systemic treatment, and they are provided for the different levels of health care.
The choice of treatment (picture 37) depends on
the psoriasis subtype and the effect it has on the patient's life
the extent, severity and location of the lesions
the availability, feasibility and cost of treatment modalities
the patient's age and life situation as well as response to earlier treatment and the possible presence of comorbidities.
The current treatment philosophy aims from the beginning to achieve permanent control of the disease, which requires earlier initiation of long-term systemic drug therapy than in the past. It aims to
minimize the cumulative impairment building up because of the disease
reduce the risks of the emergence of psoriatic arthritis and associated diseases.
Consideration should also be given to diseases and risks associated with psoriasis (e.g. metabolic syndrome and associated disorders) as well as to lifestyles with a detrimental effect on psoriasis (alcohol consumption, smoking). The total cardiovascular risk should be assessed from time to time (e.g. using the SCORE risk chart http://www.escardio.org/communities/EACPR/toolbox/health-professionals/Pages/SCORE-Risk-Charts.aspx) in all patients receiving phototherapy or systemic medication and in patients over 40 years of age.

Classification of psoriasis treatments
Topical treatment Phototherapy Systemic treatment
* = No licensed indication (i.e. not eligible for reimbursement in some countries)
Self-care
Emollients
Keratolytic agents
Dandruff shampoos
Hydrocortisone
Occlusive dressings
Natural sunlight
Home UVB light box
General practitioner/ primary health care
Vitamin D3 derivatives (calcipotriol, calcitriol)
Glucocorticoids
Combination products
UVB, broadband
UVB, narrowband
Specialist / specialised care
Calcineurin inhibitors* (tacrolimus, pimecrolimus)
UVB, broadband
UVB, narrowband
PUVA, topical
Primary:
Acitretin
Methotrexate
Ciclosporin
Secondary:
Apremilast
Deucravacitinib
Dimethyl fumarate
Biologicals

	Topical treatment	Phototherapy	Systemic treatment
* = No licensed indication (i.e. not eligible for reimbursement in some countries)
Self-care	Emollients Keratolytic agents Dandruff shampoos Hydrocortisone Occlusive dressings	Natural sunlight Home UVB light box
General practitioner/ primary health care	Vitamin D3 derivatives (calcipotriol, calcitriol) Glucocorticoids Combination products	UVB, broadband UVB, narrowband
Specialist / specialised care	Calcineurin inhibitors* (tacrolimus, pimecrolimus)	UVB, broadband UVB, narrowband PUVA, topical	Primary: Acitretin Methotrexate Ciclosporin Secondary: Apremilast Deucravacitinib Dimethyl fumarate Biologicals

Topical treatment

Topical treatment is the main form of treatment available for a general practitioner, and in most cases it is all that is needed for psoriasis management.
Ointments and creams may also enhance the effect of other treatment regimes.

Plaque psoriasis

Emollients http://www.dynamed.com/condition/psoriasis#SKIN_CARE may be used either simultaneously with other treatments or as follow-up treatment. In very mild cases they may suffice as the sole treatment form.
Topical preparations of vitamin D (calcitriol) and its derivatives (calcipotriol that may require a special license) http://www.dynamed.com/condition/psoriasis#VITDANAL are efficient and safe in long-term management of plaque psoriasis Corticosteroids and Vitamin D Analogues for Chronic Plaque Psoriasis. Local skin reactions may occur. The use of topical vitamin D may be hampered by the need to apply the preparation regularly twice daily in order to achieve full efficacy and, moreover, treatment response will not be evident until after 4-6 weeks. This is the safest and most recommended treatment form, but only a few patients are able to continue long-term with the regular applications.
Topical glucocorticoids http://www.dynamed.com/condition/psoriasis#TOPSTEROIDS (potent to very potent, i.e. group III-IV) have a rapid onset of action and will also alleviate itchiness, which is present in about 70% of patients. They should initially be used continuously for 2-4 weeks followed by gradual dose reduction and cessation. Abrupt cessation should be avoided as it will lead to early recurrence. An attempt must be made to avoid the emergence of known adverse effects of long-term use and the patient must be appropriately monitored.
The combination product of calcipotriol and betamethasone dipropionate http://www.dynamed.com/condition/psoriasis#TOPIC_ND5_2JM_J4B is the fasted and most effective topical treatment for plaque psoriasis Corticosteroids and Vitamin D Analogues for Chronic Plaque Psoriasis. Foam is the most effective preparation type. Once daily application is sufficient. The initial treatment period lasts for 4 weeks and should be followed by one of the following studied maintenance regimes:
calcipotriol or calcitriol once or twice daily long-term
the combination product on weekends or
the combination product when required.
Occlusive dressings used alone with no added medication have been reported to be effective in localised plaque psoriasis. They may enhance the efficacy of glucocorticoid preparations, particularly when treating isolated persistent plaques.
In a 52-week study, 4.8% of users developed glucocorticoid-induced adverse effects.

Plaque psoriasis in specific areas

Scalp psoriasis (pictures 38 39) is treated with frequent shampooing (periodically, using an anti-dandruff shampoo). If necessary, salicylic acid exfoliation may be used initially followed by a glucocorticoid solution or a combined preparation.
A layer of scales will prevent the penetration of medicated preparations.
Salicylic acid is often used as a 5-10% mixture (prepared in the pharmacy) in a cream, castor oil or macrogol ointment base.
Psoriasis on the face may be treated by
moderately potent glucocorticoid preparations
pimecrolimus and tacrolimus (check reimbursement status) http://www.dynamed.com/condition/psoriasis#CALCINEURIN
Flexural psoriasis may be managed with the same preparations as those used on the face. Some patients may also tolerate vitamin D (calcitriol) ointment in flexural areas.
The treatment of psoriasis on the palms and the soles of the feet (pictures 40 34 41) consists of the above mentioned medicines used in plaque psoriasis. To treat hyperkeratosis, salicylic acid may be mixed up to 20% potency. In the most severe cases, a systemic drug (acitretin, methotrexate) is needed.

Guttate psoriasis

If guttate psoriasis is not very extensive, the topical treatment forms described for plaque psoriasis may be used, particularly topical glucocorticoids.
UVB phototherapy is the treatment of choice for extensive guttate psoriasis.

Pustular psoriasis and erythrodermic psoriasis

The principal treatment regime consists of systemic drugs, which may be supplemented with emollients and topical glucocorticoids.

Phototherapy Phototherapy for Psoriasis

Phototherapy http://www.dynamed.com/condition/psoriasis#PHOTOTHERAPY may be used in extensive guttate and plaque psoriasis in persons whose skin tolerates exposure to the sun and tans easily.
Certain photosensitising medications may be a contraindication for phototherapy.
Spending time in natural sunlight will alleviate psoriasis.
To achieve a good treatment response, the daily exposure to sunlight must continue for 3 weeks.
Ultraviolet B radiation (UVB treatment). The prescribing physician must be familiar with the patient's particular skin type as well as the radiation spectrum and dose rate emitted by the phototherapy equipment. Moreover, the amount of radiation exposure and the cumulative dose must be recorded. If the treatment has benefited the patient, a general practitioner may prescribe repeat sessions.
The conventional broadband UVB therapy is effective in guttate psoriasis and in mild plaque psoriasis. The therapy is not associated with an increased cancer risk.
Narrowband UVB therapy (311-313 nm) is more effective than broadband therapy and is the phototherapy of choice in psoriasis.
The treatment efficacy is as good as, or better than, that achieved with bath-PUVA (using topical psoralens).
In PUVA therapy (combining a psoralen and ultraviolet A) , the patient's skin is sensitised to light with methoxypsoralen (may require special permit) as a solution for bath sensitization. The treatment is hardly used any more in psoriasis.

Systemic drug therapy

A reimbursement system may divide systemic skin psoriasis medicines into primary and secondary ones.
Traditional drugs acitretin http://www.dynamed.com/condition/psoriasis#ACITRETIN, methotrexate http://www.dynamed.com/condition/psoriasis#METHOTREXATE and ciclosporin http://www.dynamed.com/condition/psoriasis#CYCLOSPORINE are primary drugs. Of these, methotrexate is best suited for long-term treatment. When used for a long time it reduces the increased cardiovascular risk of the patients.
Secondary drugs are all others, i.e. oral apremilast, deucravacitinib, dimethyl fumarate as well as the parenterally administered biological drugs.
Reimbursement policies may vary from country to country.
The efficacy of apremilast and dimethyl fumarate is comparable to that of methotrexate.
Apremilast is licensed also for psoriatic arthritis.
Deucravacitinib is more effective than other tablet therapies.
Biologicals for skin psoriasis http://www.dynamed.com/condition/psoriasis#BIOLOGIC_AGENTS are divided into three groups:
TNF inhibitors adalimumab, etanercept, infliximab, certolizumabpegol
IL-17 inhibitors bimekizumab, brodalumab, ixekizumab, secukinumab
IL-23 inhibitors guselkumab, risankizumab and tildrakizumab and also IL-12 inhibiting ustekinumab.

Referral to specialist

Children affected by psoriasis (pictures 10 1) and patients with psoriasis not responding to usual treatment modalities
A young person with recently developed psoriasis that affects the skin extensively or in visible areas of the skin.
Suspicion of excessive glucocorticoid use (pictures 42 43)
An experienced dermatologist can be more helpful in the diagnosis of problematic psoriasis than sending off a skin biopsy.

References

Krueger JG, McInnes IB, Blauvelt A. Tyrosine kinase 2 and Janus kinase-signal transducer and activator of transcription signaling and inhibition in plaque psoriasis. J Am Acad Dermatol 2022;86(1):148-157.
Griffiths CEM, Armstrong AW, Gudjonsson JE, et al. Psoriasis. Lancet 2021;397(10281):1301-1315.
World Health Organization. Global Report on Psoriasis 2016. ISBN 978 92 4 156518 9 http://apps.who.int/iris/bitstream/handle/10665/204417/9789241565189_eng.pdf (accessed 31 May 2023).

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