Psoriasis

Introduction

Psoriasis is a chronic, relapsing, inflammatory disorder characterized by a variety of morphological lesions that present in a number of forms. The most common form of psoriasis is plaque psoriasis, accounting for about 80% to 90% of cases.

  • Plaque psoriasis typically presents with characteristic salmon-pink lesions with silvery-white scales and well-defined boundaries.
  • Scalp psoriasis can be mild, exhibiting slight redness of the scalp, to severe, with total head involvement, marked inflammation and thick scaling.

Psoriasis

Occasionally, psoriasis is provoked or exacerbated by drugs such as lithium, chloroquine and hydroxychloroquine, beta-blockers, NSAIDs and ACE inhibitors.

  • Psoriasis may not be seen until the drug has been taken for weeks or months.



Management

Patients should be counselled to stop smoking and limit alcohol.

For most patients, the initial decision point around therapy will be between local (topical) and full body (phototherapy or systemic) therapy.

  • However, even patients on systemic therapy will likely continue to need some topical agents.
  • Topical therapy may provide symptomatic relief and can help minimize required doses of systemic medications.



Topical Treatment

Offer topical treatment first-line to all patients with psoriasis. The selection of treatment may depend on body site, choice of vehicle, extent and severity of the psoriasis.

Emollients

  • Moisturise dry skin, reduce scaling and relieve itching.
  • No published literature appears to have addressed emollient efficacy or whether one emollient is superior to another in treating psoriasis.
  • All emollients should be regularly and liberally applied, with no upper limit on how often they can be used.

Topical corticosteroids

  • Choose the type and potency of corticosteroid product based on disease severity and location, and the patient's age.

Coal tar preparations

  • Has antiinflammatory, antipruritic and anti-scaling properties and is often combined with other topical treatments for psoriasis.
  • Limited use because of poor patient acceptance due to cosmetic issues such as smell, staining of skin and clothes, and mess of application.
  • There has been concern over topical coal tar products' association with an increased risk of skin cancer, although this appears to be unfounded.

Keratolytics (e.g. salicylic acid and lactic acid)

  • Reduces scaling to allow other topical treatments (e.g. coal tar and corticosteroids) to penetrate.
  • Salicylic acid deactivates calcipotriol. If combined use is required, apply them at a different time of day.

Topical vitamin D analogue

  • Calcipotriol has similar efficacy to potent or very potent corticosteroids and is more effective than coal tar. May be used with topical corticosteroids.
  • Total calcipotriol dose should not exceed 5 mg/week.

Topical calcineurin inhibitors (e.g. tacrolimus 0.1% and pimecrolimus 1%)

  • Are effective in the treatment of psoriasis in sensitive areas (e.g. facial and intertriginous areas) (Off-label use).



Systemic Treatment

Systemic treatments have potentially serious adverse effects and should be prescribed only by a dermatologist.

  • Acitretin (systemic retinoids)
    • Is most effective in treating pustular and erythrodermic psoriasis; less effective in treating plaque psoriasis.
    • The onset of effect is relatively slow; the full benefit of acitretin may not be evident for 3 to 6 months.
    • Is a known teratogen (pregnancy should be avoided within 3 years of termination of use).
  • Immunosuppressive or immunomodulatory drugs
  • JAK inhibitor
    • e.g. deucravacitinib
  • Biological drugs
    • anti-TNF- α agents, e.g. adalimumab, etanercept, infliximab, certolizumab pegol
    • anti-IL-12/23 antibody, e.g. ustekinumab
    • anti-IL-23/39 antibody, e.g. guselkumab, tildrakizumab, risankizumab
    • anti-IL-17A antibody, e.g. secukinumab, ixekizumab
    • anti-IL-17A and anti-IL-17F antibody, e.g. bimekizumab
    • anti-IL-17 receptor antibody, e.g. brodalumab



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