Psoriasis: An Overview and Chronic Plaque Psoriasis

Overview

This Guidelines summary covers information from the Primary Care Dermatology Society (PCDS) guideline on the management and treatment of psoriasis, including links to further resources.

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Pathological Features

• Psoriasis is a common, genetically determined, inflammatory, and proliferative disorder of the skin, the most characteristic lesions consisting of chronic, sharply demarcated, dull-red scaly plaques, particularly on the extensor prominences and on the scalp
• Morphological variants are common. An assessment of any patient with psoriasis should include disease severity; the impact of disease on physical, psychological, and social wellbeing; whether they have psoriatic arthritis; and targeting modifiable risk factors for cardiovascular disease. 

Aetiology

• Genetic factors are important, especially in the younger age group—a family history is present in 40–50% of cases, and up to 75% if onset is before age 20 years
• There is a high concordance in monozygotic twins and lesser (15–20%) in dizygotic twins
• Lifetime risk—4% if no family history, 28% if one parent affected, 65% if both parents affected.

Triggers

• Stress—strongly associated with psoriasis
• Alcohol—heavy drinking is more common in patients with psoriasis. Excessive alcohol may have a direct effect on psoriasis; in addition, reduced compliance with treatment is likely to exacerbate symptoms
• Smoking—is a risk for both palmoplantar pustulosis and chronic plaque psoriasis
• Trauma—psoriasis can occur at the site of skin injury (Köebner phenomenon)
• Streptococcal infection, especially of the throat, is well known to provoke guttate psoriasis
• Severe or recalcitrant psoriasis is an identified HIV indicator condition
• Drugs—a wide range of drugs are said to aggravate psoriasis. The most notable associations include lithium, certain antimalarials such as hydroxychloroquine, terbinafine, beta-blockers, tumour necrosis factor inhibitors, and interferons 
• Pregnancy—if psoriasis alters, it is more likely to improve in pregnancy but get worse postpartum
• Sunlight—although sunlight is generally beneficial, a small minority have symptoms provoked by strong sunlight.

History

Skin 

• Psoriasis may develop at any age, although it most frequently presents in young adults as well as in the sixth and seventh decades
• It is generally asymptomatic, although some patients experience itch.

Psoriatic Arthropathy

• All patients should be assessed for psoriatic arthropathy (for example, by using the PEST score) at the time of diagnosis of psoriasis, and then annually—early intervention can reduce joint damage. Refer to the related PCDS chapter, Psoriatic arthritis more information.

Clinical Findings

Distribution of Plaques 

• Symmetrical
• Extensor surfaces or can be widespread.

Morphology

• Most cases of chronic plaque psoriasis are described as large plaque psoriasis or small plaque psoriasis
• Plaques are ruby red and well defined with a silvery (or grey in pigmented skin) surface scale. The plaques can join to involve very extensive areas of the skin, particularly on the trunk and limbs
• Auspitz sign—when adherent psoriatic scales are scraped or picked off, pinpoint bleeding, known as the Auspitz sign—may occur from capillaries that undulate vertically throughout the thickened psoriatic skin
• Lesions on lower legs may be less typical.

Investigations

• Severe or recalcitrant psoriasis is an identified HIV indicator condition. Early diagnosis improves treatment outcomes and reduces the risk of transmission to other people. NICE guidance and British HIV Association guidance recommends an HIV test in the following cases: 
  • new onset of severe psoriasis 
  • unusual or atypical presentations of psoriasis
  • not responding to treatment as one would expect—if there is a tendency for no or minimal response to standard treatments, then the clinician needs to think of other underlying causes that make the condition 'recalcitrant', such as HIV.

Management

Step 1: General Measures 

• As with other chronic skin conditions, time is needed by the GP or practice nurse to discuss the condition
• Refer to the patient information leaflet on psoriasis
• Advise on a prescription prepayment certificate when ongoing prescribed treatment may be required, and when appropriate.

Step 2: Assess for Related Comorbidities

Psoriatic Arthritis

• Recent studies suggest that the prevalence of psoriatic arthritis in patients with psoriasis may be up to 30%
• Patients with psoriatic arthritis should receive prompt treatment so as to help reduce the long-term complications of joint destruction.

Cardiovascular Disease

• There is a good evidence pointing to an association between psoriasis and cardiovascular disease. The risk appears greater in cases of severe psoriasis, and also in patients with psoriatic arthritis
• It is important that healthcare professionals working with patients with psoriasis, including in cardiology, dermatology, and general practice, need to target modifiable risk factors and have a lower threshold for investigating patients with cardiovascular symptoms.

Step 3: Emollients

• Prescribe copious emollients—these make the skin more comfortable and reduce the amount of scale
• The active treatments below should be used for psoriasis flare-ups until the plaques are controlled, with a treatment holiday between flare-ups in which the use of regular emollients should still be encouraged.

Step 4: Active Topical Treatments

Standard Plaques

• Many GPs and GPs with extended roles use calcipotriol and betamethasone (potent steroid) combination products first line to encourage a rapid improvement and hence adherence in chronic plaque psoriasis. Note: PCDS advice differs from the NICE psoriasis guideline, which suggests starting with its individual components
• The combination product Enstilar^® foam is often considered a first-line option for chronic plaque psoriasis on the body and the scalp—patients should be advised to shake the can well before application, and warned that the product is flammable. Other options include Wynzora cream^® (preferred by some patients as it is less greasy), Dovobet gel^®, and Dovobet ointment^®. Appropriate quantities (that is, 2 x 60g) should be prescribed
• Such therapy should be discontinued when the skin feels smooth even though still looking pink-red. Some patients benefit from Enstilar^® twice weekly maintenance therapy until the next flare, when the frequency of application should be increased to once a day 
• Dovobet gel^® may also be considered for the scalp, and can also be used on the body if preferred to other formulations 
• In patients presenting with lesions that have very thick scale, it may be necessary to use descaling agents prior to commencing the treatments referred to above. One such treatment is 5% salicylic acid in yellow soft paraffin applied twice daily until the scale thins—this can be very expensive if dispensed in the community, and there is often substantial variations in cost across different pharmacies. The combination of a potent steroid with salicylic acid (Diprosalic^® ointment) is a useful addition for moderately scaly lesions. On the scalp, sebco or cocois ointments can be used for descaling—for more detail about management of scalp psoriasis, see the PCDS chapter, Psoriasis: scalp psoriasis.

Thinner Areas of Skin

• Products containing betamethasone (a potent steroid) are best avoided on areas of thin skin, for example, the face, flexures, and the genitalia. Care also needs to be given when treating long-term plaques on the shins
  • tacrolimus 0.1% ointment once daily to twice daily is often effective for the faces—refer to the PCDS chapter, Psoriasis: facial psoriasis
  • calcitriol (Silkis^®) may be more acceptable on the flexures and genitalia because calcipotriol (Dovonex^®) can be irritant, especially on these sensitive areas. Calcitriol can also be used on the genitalia. A moderate-potency topical steroid, such as Eumovate cream^®, can also be used for flares at these sites—refer to the PCDS chapter, Psoriasis: Flexural and Genital
  • tar preparations (for example, Exorex^® lotion) may be preferable for large thin plaques, such as for longer-term use on the shins, or used more generally in patients presenting with very large numbers of small plaques, where it is often difficult to treat lesions individually with a steroid product.

Other Treatments Options

• Dithranol preparations remain the most effective topical treatments (especially for solitary plaques), but patient acceptability limits their use; dithranol can be very messy, and can leave the treated areas more deeply pigmented for some time after the treatment is complete. See the PCDS patient information leaflet on how to use dithranol preparations (note: Dithrocream^® has been discontinued).

Step 5: Second-Line Treatments 

• Patients with moderate-to-severe psoriasis at the onset and those who fail to respond adequately to topical treatments should be referred for consideration of second-line treatments, which include:
  • phototherapy—most patients receive narrow band ultraviolet B (UVB) known as TL-01 therapy. UVA therapy by way of psoralen and UVA is sometimes used. There is a maximum dose of light therapy that a patient may receive in a lifetime to limit the risks of skin cancer; this is especially the case in Caucasian patients. In pigmented skin, phototherapy can sometimes aggravate psoriasis causing hyperpigmentation
  • ciclosporin—acts quickly. It is an immunosuppressive agent, and so is best used in younger patients who have not already received light therapy. The main risks are of hypertension and renal damage, which limit how long the treatment can be given for. It can be used in 3-monthly pulses to extend its use
  • methotrexate is still one of the most effective treatments, and it can also help some patients with psoriatic arthritis. The main risks are liver damage and bone marrow suppression, which can occur in the early stages of treatment—patients should be advised to report immediately for a full blood count if they have a sore throat or other signs of infection. Methotrexate cannot be used in pregnancy
  • acitretin is one of the mildest but safest treatments. It can be particularly useful in hyperkeratotic hand/foot psoriasis. Acitretin is highly teratogenic, and pregnancy needs to be avoided while on acitretin and for 2 years after. For this reason it is generally avoided in women of childbearing age
  • other drugs include the fumarates, apremilast, and hydroxyurea.

Step 6: Biologics and Biosimilars

• Biologics and biosimilars are used for both psoriasis and psoriatic arthritis. They work by interfering with specific components of the autoimmune response. Unlike general immunosuppressants that suppress the entire immune system, biologics fight more selectively and target only those chemicals involved in causing psoriasis
• There is an increasing list of such drugs—the evidence around which treatment is best for any given patient is ever evolving 
• Although biologics and biosimilars are effective for many patients with moderate-to-severe psoriasis, their long-term effects are as yet unknown, and so they are used only in accordance with NICE guidance. This means that they are reserved for patients who have been treated with second-line treatments (step 5), and where these have either been ineffective or not tolerated.

Other Resources

• The PCDS Psoriasis primary care treatment pathway
• Psoriasis decision aid—this project was initiated and funded by Bristol Myers Squibb. This shared decision aid is for patients who have been diagnosed with psoriasis when talking to their healthcare professionals. The decision on what to prescribe lies with the relevant healthcare professional at all times. This shared decision aid has been endorsed by the PCDS
• Fast facts: psychodermatological aspects of psoriasis
• Patient support groups—The Psoriasis Association
• For more in-depth reading, refer to the SIGN guideline on psoriasis.