Chronic Plaque Psoriasis

Synonyms: Psoriasis Vulgaris (Chronic Stationary Type)

Psoriasis is a common, chronic, relapsing, inflammatory skin disorder with a strong genetic basis.
Plaque psoriasis is the most common type of psoriasis (90% of all psoriasis).

Plaque psoriasis can affect persons of any race; however, epidemiologic studies have shown a higher prevalence in western European and Scandinavian populations. In these groups, 1.5-3% of the population is affected by the disease, most cases are mild in severity.^1,2 Psoriasis is thought to be rare in West Africans.

Male and females are equally affected, and there are two peaks of incidence, the first in young adults (aged 16-22) and the second in older individuals (aged 57-60).

Risk factors

Both genetic and environmental factors have been implicated in the pathophysiology of psoriasis.

• Genetic factors: HLA-B13, B17, and Cw6 are all associated with plaque psoriasis. Studies of twin siblings have supported the role of genetic factors but also suggested that environmental factors also play a role in the aetiology of plaque psoriasis. Identical twins have a 70% concordance compared with 20% in non-identical twins.
• Environmental factors: a number of factors may exacerbate plaque psoriasis, including:
  • Trauma
  • Sunlight: there is usually a decrease in severity during periods of increased sun exposure (i.e. is often improves in the summer and is worse in the winter). A small minority have an aggravation of symptoms during strong sunlight. Sunburn can also lead to an exacerbation of plaque psoriasis
  • Infection, e.g. streptococcal, HIV infection
  • Psychological stress
  • Drugs: e.g. alcohol, lithium, chloroquine and withdrawal of systemic steroids. On occasions some beta-adrenoreceptor blocking drugs, non-steroidal anti-inflammatory drugs and ACE inhibitors have also been implicated
  • Smoking and alcohol

• Plaque psoriasis may present at any age, with peaks in early adulthood and late fifties:
  • It typically causes itchy, well demarcated circular-to-oval red/pink elevated lesions (plaques) with overlying white or silvery scale, distributed symmetrically over extensor body surfaces and the scalp.
  • The extent and duration of the disease is very variable. Lesions vary in size from one to several centimeters. The number of lesions may range from few to many at any given time. Smaller plaques may coalesce into larger lesions, especially on the legs and sacral regions.
  • Fissuring within plaques can occur when lesions are present over joint lines or on the palms and soles.
  • Gentle scraping accentuates the scale (vigorous scraping causes pinpoint bleeding - Auspitz sign).
  • New lesions often appear at sites of injury or trauma to the skin (Koebner reaction), which typically occurs 1-2 weeks after the skin has been injured.
• Plaque psoriasis presents slightly differently in children. Plaques are not as thick, and the lesions are less scaly. Psoriasis may often appear in the nappy region in infancy and in flexural areas in children. The disease more commonly affects the face in children than with adults.
• Nail changes are often seen, with pitting, onycholysis, subungual hyperkeratosis, or the oil-drop sign (yellow-red discolouration of nail bed looking like a drop of oil beneath the nail).³

Acute episodes of plaque psoriasis may evolve into more severe disease, e.g. pustular or erythrodermic psoriasis.

• The psoriatic lesions are a very distinctive rich, full, red colour. When present on the legs, lesions sometimes carry a blue or violaceous tint.
• Psoriatic plaques occasionally appear to be immediately encircled by a paler peripheral zone.

• Bowen disease
• Cutaneous T-Cell lymphoma
• Drug eruptions
• Lichen planus
• Discoid lupus erythematosus
• Dermatitis
• Pityriasis rosea
• Seborrheic dermatitis
• Syphilis
• Superficial basal cell carcinoma

Diagnosis is usually made on clinical findings. Skin biopsy is very rarely required to confirm diagnosis.

Psoriasis may profoundly affect all aspects of patients' social and personal lives as well as their work.² Impact is not directly related to the overall area affected or disease activity, but more to the site distribution and the attitudes of the patient.

• Give a full explanation of psoriasis, including reassurance that it is neither infectious nor malignant, with appropriate written patient information.
• Discuss treatment options (including no active treatment), likely benefit from treatment and side-effects. Ideally agree a management plan. Include techniques of application of any topical treatment (especially important with dithranol and scalp preparations) .
• An introduction to patient support groups may be helpful.²

The Dermatology Life Quality Index (DLQI) may be a useful tool to assess disability and efficacy of treatment.⁴
A DLQI of 10 or more correlates well with severe disease requiring admission, phototherapy or second line therapy and an improvement in DLQI of 5 or more points is considered a worthwhile criterion for response.²

Topical treatment²

Non-irritant thick emollients - use liberally and frequently (apply 3-4 times a day in direction of hair growth) to soften and reduce scaling and irritation. Use combination of bath oil, soap substitute and emollient (adults with generalised disease will need 500 g emollient/week). Ideally patients should have a daily soak in the bath (with bath oil), then pat their skin dry, and then apply a thick layer of emollient.

In general, one uses milder agents for flexures, e.g. low potency topical steroids, mild tar preparations, and tacalcitol or calcitriol (not calcipotriol, this is usually irritant in flexures).
In facial psoriasis, use mild agents: emollients, mild corticosteroids, calcitriol, tacalcitol, mild tars.

For localised plaque psoriasis, e.g. on the elbows or knees, one or more of the following topical preparations can be tried. The sequence of choice will vary according to the extent and pattern of psoriasis, and patient preference:²

• A tar-based cream, or a tar/corticosteroid mixture (most are relatively mild; stronger tar preparations tend to be messy). Preparations with between 1% and 5% are as effective as stronger ones.
• A moderate potency topical corticosteroid (e.g. 0.05% clobetasone butyrate): stronger agents can be used on palms and soles or on the scalp. Use of topical steroids may lead to rebound exacerbation when treatment is discontinued.
• A vitamin D analogue e.g. calcipotriol, calcitriol or tacalcitol - the latter two tend to be less irritant and are more suitable for face or flexures, but should still be used with caution.²
  • Improvement generally occurs within 2 weeks, but improvement frequently reaches plateau at 8 weeks. Do not exceed maximum recommended dosage (risk of vitamin D excess).
  • Calcipotriol with steroid betamethasone dipropionate is available as a combination product - Dovobet® (note that long-term data regarding relapse rates is not yet established).
    • Not ideal for use on face or genitals, nor children aged under 18 (because of potency of steroid).
    • It is normally used in the initial treatment of stable plaque psoriasis where calcipotriol has failed. Patients should use it once daily to a maximum of 30% of their body surface (max 15 g daily, max 100 g weekly), for a maximum of 4 consecutive weeks.
    • After this period consider switching back to vitamin D analogue ±less potent steroid. A frequent compromise is to use the combined product for 4 weeks alternating with 4 week periods of just Calcipotriol. Over the whole year this produces the best results with the least side-effects.
    National guidelines² warn that potent topical corticosteroids should be avoided or given only under specialist supervision in psoriasis because, although they may suppress the psoriasis in the short term, relapse or vigorous rebound occurs on withdrawal (sometimes precipitating severe pustular psoriasis). Topical use of potent corticosteroids on widespread psoriasis can lead to systemic as well as to local side-effects.
• A vitamin A analogue (retinoid) - tazarotene: this is clean and odourless. Irritation is common but it is minimised by applying tazarotene sparingly to the plaques and avoiding normal skin. It should not be used by pregnant women or women planning a pregnancy (teratogenic fears).
• A dithranol preparation is applied carefully to lesions avoiding contact with normal skin. These regimens are effective but more difficult to use, especially if there are many small lesions. They are usually carried out under hospital supervision, starting at low concentration and gradually building up as tolerated, reducing if the patient experiences any burning.⁵ Patients need to be shown how to apply creams carefully to minimise side-effects (skin irritation and temporary skin staining). Products can cause permanent staining of fabrics and bath.
  • Standard regimen - dithranol is applied to plaques in gradually increasing concentrations (0.1-2%) in a non-smudging zinc oxide (Lassar's) paste. This is applied by a trained nurse or tutored patient, covered with powder and stockinette to reduce smearing, and left in place for up to 24 hours. Treatment is frequently combined with UVB phototherapy and a tar bath (the Ingram regimen). Patients with plaque psoriasis respond after approximately 20 days of treatment, and relapse at a rate of 10% per month
  • Short-contact regimen involves higher concentrations, building from 1-10% (as tolerated), for 15-20 minutes/day with subsequent wash-off. This allows enough dithranol to remain fixed to the plaques for clinical benefit without any special dressings. There is less risk of smudging dithranol onto peri-lesional skin, but skin irritation may still occur during wash-off.

For more widespread plaque psoriasis, the same treatments may be appropriate but dithranol is often impracticable to apply to multiple small lesions and will irritate flexures, and topical corticosteroids may be inappropriate for use in widespread psoriasis, particularly more potent agents if used on a long-term basis.

Scalp psoriasis²

Try a tar-based shampoo first (can be combined with a 2-5% salicylic acid preparation, a coconut oil/tar/salicylic acid combination ointment, a potent topical corticosteroid preparation (e.g. 0.1% betamethasone valerate), or a calcipotriol scalp application).

It is important to use a keratolytic agent (e.g. 5% salicylic acid in emulsifying ointment) first when there is significant scaling, or other treatments will fail. Keratolytic creams should be applied for a few hours or overnight. A different treatment for day- and night-time is a useful approach.

• Phototherapy is a second line treatment and should only be used for extensive and widespread disease. Resistance to topical treatment is another indication for phototherapy:^2,6
  • Narrow-band UVB therapy offers superior efficacy with less risk of burning. UVB phototherapy is extremely effective for treating moderate-to-severe plaque psoriasis.
    • UVB therapy is usually combined with one or more topical treatments. UVB is often combined with topical corticosteroids, calcipotriene, tazarotene, or simply bland emollients.
    • The major drawback of this therapy is the time commitment required for treatments and the accessibility of the UVB equipment. Home ultraviolet therapy can overcome some of the problems of time and convenience but they are expensive.
  • PUVA photochemotherapy uses the photosensitising drug e.g. methoxsalen (8-methoxypsoralens) in combination with UVA irradiation to treat patients with more extensive disease. Therapy is usually administered 2-3 times per week, with maintenance treatments every 2-4 weeks until remission.
    • Adverse effects of PUVA therapy include nausea, pruritus, and a burning sensation.
    • Long-term complications include increased risks of skin damage and skin cancer.
    • PUVA has been combined with oral retinoid derivatives to decrease the cumulative dose of UVA radiation to the skin.
  • Excimer laser UVB therapy can deliver high-dose light to limited plaques.¹
• Systemic agents - Only used after both topical treatments and phototherapy have been unsuccessful and for patients with very active psoriatic arthritis or who have disease that is physically, psychologically, socially, or economically disabling.
  • Methotrexate is useful in acute, generalised, pustular psoriasis, psoriatic erythroderma, psoriatic arthritis, and for extensive chronic plaque psoriasis in patients who are inadequately controlled by topical therapy alone.²
  • Ciclosporin may be employed either as a maintenance treatment, using long-term continuous therapy, or as a short course of treatment for 4 to 12 weeks, to induce remission, which might then be repeated later following relapse.²
  • Hydroxycarbamide is a second line modality for the treatment of psoriasis and is usually reserved for cases where other second line agents have failed or are contraindicated.²
  • Acitretin: is an oral retinoid. It is indicated for severe extensive psoriasis resistant to other forms of therapy. It is only moderately effective in many cases and it is therefore usually combined with other treatments.²
• Biological therapies - for psoriasis comprise two main groups:²
  • Agents targeting the cytokine Tumour Necrosis Factor (TNF-alpha) (e.g. etanercept, infliximab,⁷ adalimumab). Etanercept should be considered for treating adults with severe plaque psoriasis when other treatments have been ineffective or contraindicated. If there has been no definite improvement with etanercept after 12 weeks, the treatment should be stopped.⁸
  • Agents targeting T-cells or antigen-presenting cells (e.g. efalizumab, alefacept). Efalizumab should be considered for treating adults with severe plaque psoriasis when other treatments have been ineffective or contraindicated, and etanercept treatment has been ineffective.⁸

• The quality of life may be severely affected by pruritus, dry and peeling skin, fissuring, and the adverse effects of therapy.
• Self-consciousness and embarrassment about appearance may lead to significant anxiety and depression.
• Aggressive use of topical steroids may induce progression to pustular and erythrodermic forms of psoriasis.
• Psoriatic Arthropathy - up to 30% of patients with chronic plaque psoriasis may also have psoriatic arthritis.⁹ May present without skin lesions, typically affects small finger joints, may affect single or multiple larger joints, or sacroiliitis.

• The course of plaque psoriasis is unpredictable. It is often intractable to treatment, with relapses occurring in most patients.
• Both early onset and a family history of disease are considered poor prognostic indicators.
• Pustular flares of disease may be provoked by systemic corticosteroid therapy. Such flares can be fatal. Disease-related mortality is otherwise very rare in psoriasis.
• Adverse effects of systemic treatments (e.g. hepatic fibrosis from methotrexate) and phototherapy (eg PUVA-induced skin cancers with metastases) are the primary disease-related causes of death.

• Avoiding specific exacerbating factors may help prevent or minimise flare-ups but the cause of disease exacerbation is often unknown.