Psoriasis

Definition Chronic plaque psoriasis (psoriasis vulgaris) is a chronic inflammatory skin disease characterised by well demarcated erythematous scaly patches on the extensor surfaces of the body and scalp Lesions may itch, sting and occasionally bleed Dystrophic nail changes are found in > 1/3 Psoriatic arthropathy occurs in 1->10% Condition waxes and wanes with wide variations between individuals Other types – guttate, inverse, pustular, erythrodermic

Epidemiology of psoriasis Affects 1.5% in UK Ethnic variation – Rare in Japan and China M = F Bimodal age distribution – Commonest between 10 and 20 years and around 50 years Many cases mild Can be very stigmatising 5% get episodes of severe disease Precipitants / aggravants – Alcohol, NSAIDs, B blockers, Lithium, antimalarials

Pathology Rapid proliferation of keratinocytes (x7 normal rate) causes acanthosis = thickening of epidermis due to increased numbers of acanthocytes (prickle cells) Incomplete differentiation and maturation causes cells to be shed in abnormally large clumps Dilatation and elongation of capillaries – apparent at surface Infiltration of dermis and epidermis by inflammatory cells causes microabscesses and micropustules : pustular psoriasis Cause unknown. Though to be autoimmune – genetic influence – 30% have a relative with the condition

Chronic plaque psoriasis Commonest type Scaly erythematous plaques – red, white-silver scale, well demarcated Itch common, pain unusual Symmetrical distribution Common sites – Scalp, elbows, knees, shins and sacrum Nail involvement common Koebner’s phenomenon useful pointer Activity varies over months to years, remission common, sometimes induced by treatment

Guttate psoriasis Acute eruption of small plaques (typically 1cm) over trunk and limbs Triggered by URTI – particularly streptococcal sore throat

Palmopustular psoriasis More often affects women Strong correlation with smoking Chronic relapsing course, difficult to treat (often needs systemic treatment) Can be painful When occurs on its own, difficult to distinguish from eczema

Nail psoriasis Pitting and onycholysis, subungal hyperkeratosis Can occur in isolation

Flexural and genital psoriasis Looks different, not always scaly Exudation prominent

Scalp psoriasis

Severe types / manifestations of psoriasis Generalised pustular psoriasis – Often erupts suddenly. Life-threatening – Some cases associated with withdrawal of topical or systemic steroids – Sheets of small pustules merge – Associated pyrexia and systemic illness – Sepicaemia, shock, dehydration can occur Erythrodermic psoriasis – Usually seen in neglected or poorly controlled severe psoriasis – Severe erythema and scaling over entire body surface Psoriatic arthritis

General assessment – disease severity Patient satisfaction Disease related quality of life Surface area covered – <5% is mild – one palm area = 1% body area – 5-20% is moderate – often requires hospital intervention, usually topical / oral regimen with UV light therapy – >20% is severe – requires systemic therapy

Many therapies Community based Emollients Topical coal tar Topical dithranol Topical vitamin D and analogues Topical corticosteroids Topical retinoids Plus combinations Hospital led Phototherapy Methotrexate Oral retinoids Cyclosporin Hydroxyurea Azathioprine Systemic steroids TNF-alpha drugs T-cell drugs – efalizumab, alefacept

British association of Dermatologists recommendations Emollients soften scaling and reduce irritation For localised plaque psoriasis one or more of the following can be used : – Tar based cream or tar/corticosteroid mixture – Moderate potency topical corticosteroid eg eumovate – Stronger agents can be used on the palms and soles or on the scalp – Vitamin D analogue – Calcipotriol with betamethasone dipropionate combination product – Vitamin A analogue (tazarotene) – Dithranol preparation Use a keratolytic agent (eg 5% salicylic acid in emulsifying ointment) first when there is significant scaling or other treatments fail

Topical tar Newer ‘cleaner’ creams more acceptable – up to 10% coal tar Stronger ‘crude’ preparations are usually part of hospital based treatment Shampoo particularly useful Traditionally been used combined with UVB therapy (Goeckermann treatment) Trend towards alternating applications with topical steroids Expensive now! Tried and tested (100 years plus) Smelly Can stain clothing and skin Safety concerns (no long term evidence of increased cancer risk)

Dithranol Best suited to largeish, well- defined plaques Not for flexures Start with low strength and build up, from 0.1 up to 3% Miconal is a newer product claiming to release dithranol at body temp (and causes less staining) Apply for 30 mins and wash off )vary between 5 and 60 mins Tried and tested (50y) Cheap Not easy to use Wear gloves or wash off hands carefully Irritating and can ‘burn’ healthy skin Stains (brown/purple) – skin, clothes, bath etc

Vitamin D and analogues Calcipotriol – OD or BD – Irritation – redness, soreness and pruritis common (20%) – Not to be used on face or flexures – No more than 100g per week (risk of hypercalcaemia) Calcitriol – BD – Max 30g daily – Not children – Can be used on creases and face Tacalcitol – Once daily – Not children – Max 10g per day – Can be used on creases and face

Topical steroids Effective in short term, relatively cheap Generally liked by patients – not smelly / messy Early improvement not sustained Do not use more than 4 weeks Problem is rebound effects or aggrevation /instability Mild steroid useful for creases and face Potent steroid often useful as initial treatment for scalp, hands and feet Can be used with dithranol, coal tar, vitamin D and analogues Dovobet allows steroid and calcipotriol application at the same time

Dovobet – betamethasone 0.05% with calcipotriol OD or BD Indicated for stable plaque psoriasis (age greater than 18) Not to be applied to scalp, face, mouth (or eyes) – also avoid creases Max 4 weeks, max 15g/day, 100g/week No more than 30% of total body surface

Tazarotene (Zorac) Indicated for mild to moderate plaque psoriasis affecting up to 10% of skin area OD up to 12 weeks ; not on face Not recommended under 18 Teratogenic – must not be used in pregnancy Helps regulate abnormal proliferation of keratocytes Can be quite irritant but is clean and convenient DTB advise not using first line Potential for use in combination therapy

Trend is towards combination therapy All topical therapies have limitations – Irritation, staining, smell, inconvenience etc Most work through different mechanisms so effects might be additive or synergistic Potential for combining approaches – Improving therapeutic effects – Minimizing adverse effects

Special sites – skin creases, genitals Tricky to diagnose and treat Appearance may not be typical – erythema prominent, scale not evident, may ‘exude’ Topical corticosteroids often used but avoid high potency – these areas prone to skin atrophy Use creams rather than ointments Tacalcitol may be used Calcipotriol may be too irritant

Scalp Tends to be visible and stigmatising Is difficult to manage Soften thick scale with coconut or arachis oil, can be left on overnight, under shower cap (with salicylic acid, if required) Remove using combing and shampoo – tar based Apply coal tar, dithranol, or topical steroid preparation Newer calcipotriol scalp application is an alternative

Psoriatic arthropathy 15-20% attending hospital develop inflammatory arthritis May be <10% in the community Slight female predominance Most have pre-existing skin or nail psoriasis (joint inflammation precedes psoriasis in 15% of cases)