Psoriasis

Latest update 28/03/10  

This chapter is set out as follows:

• Introduction
• Psoriatic arthropathy
• Chronic plaque psoriasis
• Guttate psoriasis
• Generalised pustular psoriasis
• Palmoplantar pustulosis
• Specific sites:
  • Scalp
  • Face
  • Hands and Feet
  • Nails
  • Flexures and genitalia
• Psoriasis in children

Erythrodermic psoriasis is discussed in the section on erythroderma

Introduction

Definition

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 prominence and in the scalp. Morphological variants are common

Incidence and prevalence

• Affects around 3% of the population
• It is uncommon in certain populations such as oriental people, native American Indians and West Africans
• Both sexes are equally affected
• It may develop at any age although it most frequently presents in young adults and in the sixth & seventh decades

Pathophysiology

• Recent research suggests that psoriasis is an autoimmune disease
• Abnormally large numbers of T cells trigger the release of cytokines in the skin causing the inflammation, redness, itching and flaky skin patches characteristic of psoriasis

Aetiology

• Genetic factors are important, especially in the younger age group (a family history is present in 40-50% and up to 75% if onset is before age 20)
• 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

• Trauma – psoriasis at the site of injury (Köbner phenomenon)
• Infection – streptococcal infection, especially of the throat is well known to provoke guttate psoriasis. Continuing subclinical infection may also play a role in refractory chronic plaque psoriasis
• 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
• Drugs – a wide range of drug are said to affect psoriasis. The most notable associations include lithium, beta-blockers, anti-malarials and NSAIDs
• Stress – may worsen symptoms
• Alcohol – heavy drinking is more common in patients with psoriasis. It is hard to know if excessive alcohol has a direct effect on psoriasis but the reduced compliance with treatment is likely to exacerbate symptoms
• Smoking – is a risk for both palmoplantar pustulosis and chronic plaque psoriasis
• HIV – exacerbates psoriasis

Psoriatic arthropathy

Recent studies suggest that the prevalance of psoriatic arthritis in patients with psoriasis may be up to 30%. There is a strong link with nail disease

Psoriatic arthritis has been divided into five subtypes:

• Distal interphalangeal
• Symmetric polyarthritis (resembles RA)
• Asymmetric oligoarthritis – large joint
• Spondylitis
• Arthritis mutilans – a severe destructive form affecting fingers and toes

Chronic plaque psoriasis

Key diagnostic features

• Itch – patients can experience itch, although it is usually much less marked than with eczema

• Distribution:
  • Symmetrical
  • Extensor surfaces
  • Can be widespread

• Morphology:
  • Ruby-red, well-defined plaques
  • Silvery surface scale
  • Auspitz’s sign - when adherent psoriatic scales are scraped or picked off, pinpoint bleeding known as Auspitz's sign may occur. The pinpoint areas represent the tops of tiny capillaries which undulate vertically throughout the thickened psoriatic skin
  • Lesions on lower legs may be less typical

• Other affected sites: see below

	Figure 1 - Common sites for psoriasis
	Figure 2 – Chronic plaque psoriasis Well-defined deep-red plaques with surface scale
	Figure 3 – Chronic plaque psoriasis of the knees
	Figure 4 - Chronic pla que psoriasis of the upper back
	Figure 5 - Small plaque psoriasis
	Figure 6 - Close up of figure 5
	Figure 7 - Psoriasis The differential diagnosis could include Pityriasis versicolor
	Figure 8 - Psoriasis. Close up of figure 7 Closer examination clarifies the diagnosis
	Figure 9 - Auspitz sign Arrow denotes small haemorrhage that is seen following removal of scale (copied with kind permission of Danderm)
	Figure 10 - Psoriasis on lower legs
	Figure 11 – Thin plaques of psoriasis on the lower legs Suitable for treatment with a topical tar preparation
	Figure 12 – Psoriasis with large plaque right forearm
	Figure 13 – Psoriasis of the gluteal cleft
	Figure 14 – Psoriasis affecting the concha of the ear
	Figure 15 – Psoriasis affecting the umbilicus
	Figure 16 – Cutaneous T-cell lymphoma (CTCL) CTCL is one of the great mimickers of skin disease. Although it can present in many ways, lesions tend to start off flat and respond poorly to topical treatments. Over a number of years lesions become plaque-like and start to ulcerate. A biopsy of early CTCL may miss the diagnosis – unusual rashes are best referred to a specialist

Management of chronic plaque psoriasis

General points

As with other chronic skin conditions

• Time is needed by the GP / practice nurse to discuss the condition
• Provide patient information leaflets and direct to appropriate websites
• Advise on a pre-payment exemption certificate where appropriate
• 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 flares when the use of regular emollients should be still be encouraged

Guttate psoriasis

Clinical features

• Typically triggered 7-10 days after a streptococcal URTI
• It is a common pattern in children and young adults
• Distribution – even distribution over the body, especially on the trunk and proximal limbs. Relative sparing of the face
• Morphology – small, round-oval scaly lesions up to 1cm in diameter. In the early stages there may be little scale. The Köbner phenomenon may be present

Management

• In mild cases of guttate psoriasis the use of an emollient regimen may be sufficient until spontaneous clearance occurs, usually after 2-3 months. While natural sunlight in moderation can improve guttate psoriasis, the use of UV sun-beds without medical supervision is discouraged
• Topic al treatment - coal tar preparations e.g. Exorex lotion can be beneficial as they can be applied more generally to a large area of skin. Vitamin D analogues can be used but because these treatments are best applied directly to the lesions, with large numbers of lesions application is very time consuming and may not be acceptable to some patients
• Referral to dermatology for a course of narrow band UVB is an effective treatment for widespread / unresponsive cases

Prognosis

• While some will go on to develop ordinary psoriasis at a later stage, 1/3 do not have a family history and don’t go on to develop psoriasis in adulthood

	Figure 17 – Early guttate psoriasis with little scale
	Figure 18 – Guttate psoriasis

Generalised pustular psoriasis

Clinical

• Irregular red patches
• Small pustules (1-2mm)
• Systemic upset with sore skin, fever and malaise

Some cases are drug-induced and abrupt withdrawal of systemic corticosteroids or very potent topical steroids in a patient with known psoriasis is a significant risk factor

Management

• Patients are often very unwell and need admitting. The most appropriate course of action is to phone the on call dermatologist

	Figure 19 – Generalised pustular psoriasis  (copied with kind permission of Dermatoweb)
	Figure 20 – Generalised pustular psoriasis (close up)
	Figure 21 – Pustular psoriasis  (copied with kind permission of Dermatoweb)

Palmoplantar pustulosis

Incidence and aetiology

• Age - mainly presents in patients over 50
• Females > males
• Strong link with cigarette smoking (unfortunately stopping smoking does not often lead to an improvement)
• Approximately 25% have a background of chronic plaque psoriasis

Clinical

• Palms, feet (especially heel and instep) or both
• Erythematous plaques with yellow / brown pustules

Treatment

• Can be difficult
• Potent topical steroids such as 0.1% betnovate or dermovate - occulsion with clingfilm may be of benefit
• Patients failing to respond should be referred to dermatology out-patients for consideration of hand/foot phototherapy or systemic agents

	Figure 22 – Palmoplantar pustular psoriasis Sterile yellow and brown pustules
	Figure 23 – Palmoplantar pustular psoriasis
	Figure 24 – Palmoplantar pustular psoriasis  (copied with kind permission of Dermatoweb)

Specific sites – scalp

Clinical

• Plaques of psoriasis often separated by normal areas of scalp
• Scalp margins and above the ears are frequently affected

Management

• Shampoo for long-term management
  • Tar based preparations e.g. Polytar (plus) ® or Capasal ® shampoo are useful when scale is present - massage into the scalp for 5 minutes to allow shampoo to penetrate the scale and then wash out
  • Some patients are not keen on the smell of tar based preparations and may wish to try an alternative such as Dermax ® shampoo

• Some pateints present with thick scale and this needs to be removed before commencing the topical applications referred to above. Sebco ® scalp ointment is very effective at removing scale - massage into affected areas of the scalp for 5 minutes and leave on for at least 2 hours, or overnight before washing out with shampoo (some patients cannot tolerate the treatment for more than a few hours). The treatment is messy and so if left on overnight patients should use an old pillowcase or towel, alternatively the scalp can be occluded with a shower cap. Sebco may be need to be used for a few days until the scale diminishes, and then used PRN as the scale builds up. Warn patients that hair loss may occur as the scale come away, but that this will recover

• For psoriasis of the hair margins - consider 1% hydrocortisone ointment / Eumovate ® ointment BD

• Severe scalp psoriasis - patients not responding adequately to treatment should for referred to a dermatologist for consideration of other treatments such as methotrexate or intralesional steroid injections, the latter is the less effective of the two
• Please click here to view video clips of how to apply scalp treatments

	Figure 25 – Scalp psoriasis
	Figure 26 – Scalp psoriasis with hairline involvement  (copied with kind permission of Dermatoweb)
	Figure 27 – Scalp psoriasis with thick scale Sebco ointment was needed to remove the scale before other treatments could be used  (copied with kind permission of Dermatoweb)

Specific sites – face

Clinical findings

• The face is not a common site for psoriasis
• Patients occasionally present with well-demarcated plaques. A more frequent finding is similar to that seen in seborrhoeic dermatitis, indeed the two can be very difficult to tell apart and as such this presentation is sometime referred to as sebo-psoriasis

Treatment

The face, along with the hands and genitalia represent important cosmetic areas and the presence of psoriasis at these sites produces disproportionate distress. Improving psoriasis at these sites is of great importance. Treatment options include:

• Emollients
• The vitamin D analogues Curatoderm ® lotion or ointment and Silkis ® ointment
• Although weaker topical steroids such as 1% hydrocortisone or Eumovate can be used, there is a risk of atrophy and so an alternative choice is 0.1% Tacrolimus ® ointment, which although off-label when used in this context can be very effective for facial psoriasis

	Figure 28 – Facial psoriasis  (copied with kind permission of Dermatoweb)
	Figure 29 – Sebopsoriasis  (copied with kind permission of Dermatoweb)
	Figure 30 – Facial psoriasis, treated with 0.1% proptopic ointment Involvement around the eye is more common in children compared with adults
	Figure 31 – As above, 2 weeks later

Specific sites - hands and feet

Clinical findings

Psoriasis can affect the hands and feet in 3 main ways:

• As part of a general psoriasis (images 28 & 29) - manage as per chronic plaque psoriasis
• Palmoplantar pustular psoriasis - see earlier in the article
• Hyperkeratotic psoriasis (images 30 & 31)

Hyperkeratotic psoriasis – clinical findings

• In absence of other signs of psoriasis it can be difficult to differentiate from hyperkeratotic hand dermatitis (although management of the two is very similar)
• In psoriasis the plaques are usually, but not always well demarcated
• If there are any doubts about the diagnosis skin scrapings should be sent for mycology to rule out tinea

Hyperkeratotic psoriasis – management

• It often worth giving patient information leaflet on hand dermatitis – although this is not the primary diagnosis many patients will have a degree of irritant contact dermatitis and anything that can be done to make the skin more comfortable is of value
• Moisturisers and soap substitutes
• If scale is very marked (more commonly seen on the feet) this can be reduced using 5% salicylic in yellow soft paraffin twice a day - community pharmacies can send away for this to be made up (there is considerable variation in price so it is worth finding out who is most cost effective)
• For erythema and lesser degrees of scale Diprosalic ® ointment can be used OD to BD
• Using the treatments under occlusion e.g. cotton gloves for hands and clingfilm for feet can provide additional benefit
• For more patients failing to respond to treatment / or where diagnostic uncertiainty exists e.g. contact allergic dermatitis, patients should be referred to a specialist. The use of systemic treatments such as Neotigason ® (Acitretin) and Toctino ® (Alitretinoin) can lead to substantial improvement

	Figure 32 – Psoriasis
	Figure 33 – Psoriasis
	Figure 34 – Hyperkeratotic hand psoriasis  (copied with kind permission of Dermatoweb)
	Figure 35 – Hyperkeratotic hand psoriasis. Note the clear demarcation (copied with kind permission of Dermatoweb)
	Figure 36 – Hyperkeratotic hand and foot psoriasis (copied with kind permission of Dermatoweb)
	Figure 37 – Hyperkeratotic foot psoriasis

Specific sites – nails

Psoriatic nail dystrophy mainly occurs in patients whom also suffer from psoriasis of the skin. Less than 5% of patients have solely psoriasis of the nails. It commonly affects patients with psoriatic arthropathy

Clinical findings

• Pitting
• Oil drop - translucent yellow-red discoloration in the nail
• Subungual hyperkeratosis – thickening of the nail bed, may lead to onycholysis
• Onycholysis – the nail plate separates from the nail bed. The nail plate becomes white / yellow
• Beau's lines – white transverse lines
• Leuconychia – areas of white nail plate
• Nail plate crumbling

Management

• If there is any diagnostic uncertainty samples must be sent for mycology to rule out tinea. It is important to not only include nail clippings but also scrapings from the undersurface of the nail plate, otherwise many cases of tinea will be missed. It must be remembered that psoriasis and tinea of the nails can co-exist
• Treatment of nails is difficult and results are often disappointing:
  • Distal involvement - try and cut back the nail if possible then use Dovobet ointment ® or topical steroids
  • More substantial involvement (including proximal nail) - consider referral to dermatology for a trial of triamcinolone injections via Dermojet. Systemic agents such as Methotrexate are occasionally used but benefit is not guarenteed, and the risk to benefit ratio means that such treatments are rarely justified unless the patient also has moderate-severe psoriasis of the skin

	Figure 38 – Psoriasis of the nails with pitting (copied with kind permission of Dermatoweb)
	Figure 39 – Psoriasis with onycholysis (copied with kind permission of Dermatoweb)
	Figure 40 – Psoriasis with onycholysis and Beau’s lines

Specific sites - flexures and genitalia

History

• It is always important to ask if patients have genital involvement as they may not otherwise come forward with the information. Genital involvement can be very uncomfortable and can interfere with relationships

Clinical findings

• Several sites can be affected including the axillae, under the breasts, umbilicus, groins, gluteal / natal (between buttocks) cleft, around the anus, penis / scrtoum and the vulva
• Morhology – lesions in the flexures are usually symmetrical, very shiny, red and well-demarcated. If affected areas are asymmetrical and scale is present always consider tinea and send scrapings for mycology

Treatment

• Moisturisers
• Topical steroids - the skin on flexural sites and the genitalia is relatively thin and so mild topical steroids such as Eumovate ® cream are preferred options. In cases of co-existent yeast a combination product such as Trimovate ® cream should be used. Stronger topical steroids need to be used with care and only for a few days at any one time. Treatment with topical steroids should be discontinued once symptoms settle
• The overuse of topical steroids in body folds may cause striae and can result in long-term aggravation of psoriasis (tachyphylaxis)
• If there are concerns that too much topical steroid is being used it can be worth trying a vitamin-D compound such as Curatoderm ® lotion / ointment or Silkis ® ointment, the other vitamin-D compounds can cause irritation on thin skin. Another option are the calcineurin inhibitors Elidel ® cream and Protopic ® ointment (both off-label in psoriasis)
• The skin on the gluteal cleft is thicker than on the other sites and so stronger treatments can be used if needed

	Figure 41 - Flexural psoriasis Symmetrical, erythematous and shiny
	Figure 42 – Psoriasis of the penis and scrotum
	Figure 43 – Psoriasis of the vulva and groins

Psoriasis in children

• Face, especially eyes and ears
• Scalp - may be the only presenting feature
• Guttate - some patients get one or two outbreaks and do not go on to develop psoriasis in adult life. In others the psoriasis persists
• Distal limbs
• 'Nappy rash' / genital involvement - it may that some infants diagnosed as having seborrhoeic dermatitis of the nappy area may instead have psoriasis
• An eczematised form of psoriasis - the two problems may co-exist
• One digit - often associated with paronychia and nail changes. Often recalcitrant to treatment, but many improve with time
• Chronic plaque psoriasis tends to be paler with less scale but is still well demarcated

Management - many of the same treatments used in adults are used in children

Prognosis - is difficult to predict, although just because a child has bad psoriasis does not mean that they will continue to have psoriasis as an adult. Patients with psoriatic arthropathy tend to have a worse prognosis