PsoriasisDr Daniel HewittDermatologistSkin and Cancer Foundation Westmead
ObjectivesTo understand the basic pathology of psoriasisTo appreciate its different modes of presentationTo be able to list the treatment optionsTo understand that psoriasis has a significant burden on many people
PathogenesisPsoriasis is very common, affecting 1-2% of most populations.There is a strong genetic predisposition. It is due to immune stimulation and increased keratinocyte cell turnover.The epidermis is hyperplastic (thickened) and there is an infiltrate of neutrophils in early lesions, followed by lymphocytes.
Chronic plaque psoriasis has been divided into two groups base on age of onset and HLA associationsType 1 – presents in young adults. A family history is common and 80% have HLA-Cw6. The disease tends to be more severe.Type 2 – peaks in incidence at 50 – 60 years of age. Patients tend to have milder disease.Psoriasis can present at any age, but 75% present before the age of 40.
There is no single, exogenous cause but a number of triggers for psoriasis Infection - streptococcal, HIV Skin trauma- koebnerisation Drugs- lithium, NSAID’s, anti-malarials, β- blockers, interferon, systemic steroid withdrawal Stress- emotional or metabolic
Clinical featuresThe hallmark of psoriasis is a well defined scaly red plaque. This may have a “salmon pink” hue. The scale can be waxy or silvery.Psoriasis is not characteristically itchy, but can be very noticeable and greatly impair patients’ quality of life.
Categorization of psoriasisChronic plaque psoriasis – the most common form that shows the most classic featuresThe nails and scalp are frequently involvedFlexural psoriasis – involving predominately the groin and/or the axilaPustular psoriasis – can be generalized or localisedPalmoplantar psoriasisSebopsoriasis – overlapping features with seborrheic dermatitisGuttate psoriasis – many small, drop-like lesions
Natural HistoryThe course of psoriasis is variable.Generally it can be treated and sometimes cleared. In some it may not recur for several years and in others it may be very severe and disabling.Guttate psoriasis has a good prognosis.Generalized pustular psoriasis is often very difficult to treat
ManagementThere are four main categoriesGeneral measuresTopical treatmentUltraviolet treatmentSystemic agents
General measuresIt is very important for patients to look after their health generally, both to help control the psoriasis and due to its known co-morbidititiesSympathetic explanation of the disease, it’s natural history and treatment options is an essential part of managementAvoidance of stress – sometimes a hospital admission can provide a break from thisTreatment of blood pressure, cholesterol, any diabetes and weight is also important and should be assisted by the GPCessation of smokingGenerally, a balanced healthy diet and regular exercise are important
Topical treatmentsThese compriseEmollientsSteroidsVitamin D analogues – eg calcipotriolTar creamsDithranol
Simple emollients (eg sorbolene) can help with the scaling and dryness of psoriasis. Keratolytics (eg salicylic acid) can be added to these. Generally these are tolerated well but only have a mild effect on psoriasis.
Topical steroids are very helpful in managing the inflammation of psoriasis. They are especially useful in acute inflamed plaques. Weak steroids are often ineffective. However, strong steroids need to be used for limited periods as psoriasis tends to become more resistent to their use (tachyphylaxis)The strength is determined by the body site and the severity. Typical examples are…Mild flexural or facial involvement – Hydrocortisone 1% (eg sigmacort)Mild to moderate body involvement – Methylprednisolone 0.1% (eg advantan) or mometasone (eg elocon)Severe, body involved or palms and soles - Betamethasone diproprionate 0.05% (eg diprosone)
Topical calcipotriol (daivonex) is a vitamin D analogue that decreases the turnover of keratinocytes. It can be useful in the long-term treatment of psoriasis. It has a very low risk of tachyphylaxis or local side effects.One product, daivobet, combines calcipotriol with betamethasone diproprionate and is also effective for flares of psoriasis.
Coal tar, pine tar and shale tar have all been used in psoriasisCoal tar is most frequently used now and is particularly effective for chronic plaque psoriasis and scalp psoriasis. Some patients do not like the associated “tarry” smell. Occasionally they can irritate or aggravate psoriasis.Tars are often used in combination with keraolytics eg 6% LPC (liquor picis carbonis = crude coal tar) +4% salicylic acid in white soft paraffin.
Dithranol inhibits DNA synthesis and decreases the epidermal hyperproliferation of psoriasis.It produces redness and burning when applied to normal skin and can cause brown staining of the skin and clothing.It is used in combination with ultraviolet therapy in Ingram’s regime.
Ultraviolet therapySunlight has long been known to have a benefit on psoriasis.A specific wavelength, 311nm, of UVB light has been shown to have the best therapeutic effect on psoriasis while minimizing side effects.The dose is slowly titrated over 8-12 weeks until a good response is achievedMild erythema is common, but more severe sunburn-like reactions can occur. Over the long-term the skin will become more tanned and naevi become darker. There is an increased risk of skin cancer, but this is low.
Systemic treatmentsThese are only used in psoriasis failing to respond to topical or ultraviolet treatment. Patients must be monitorred closely for side effects.Methotrexate and cyclosporin are essentially immunosupressants that can be very effective but have many possible short and long term side effects.
Acitretin normalizes epidermal keratinization. It is most effective for psoriasis of the hands and feet and pustular psoriasis such as this case.
There are now four “biologic” agents available to treat psoriasis. These are injections that are approved in patients with severe psoriasis who have failed the other systemic treatments.Infliximab, etanercept and adalimumab are tumour necrosis factor alpha antagonistsUstekinumab is a interleukin 12 and interleukin 23 monoclonal antibody.These can be very effective but also have possible side effects including the risk of unusual infections.
ConclusionPsoriasis is very common.Although it does not generally cause severe symtpoms, it has a very significant psychosocial burden in many patients.Treatments are numerous and include topical treatments, ultraviolet treatment and systemic treatment.The condition is not curable but significant improvement and often clearance can be achieved.