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Psoriasis is a common chronic inflammatory immune-mediated disease that predominantly affects the skin and joints ( SIGN 2010 )
How common In the Europe and the US the estimated prevalence is 1-3 % A paper in the Canadian Family Physician reports a prevalence of 1.7 % in Canada Parisi et al 2013 report a prevalence of 1.3 % in the UK population Psoriasis can start at any age but a bimodal pattern has been noted at 16-22 and 57-60 yrs It affects both the sexes equally
It us uncommon in children ( 0.71 % ) and the majority of cases occur before the age of 35 yrs Psoriasis is more common in white people compared to other ethnicity About 20 % of people who have psoriasis may also have psoriatic arthritis.
What happens ? It is now thought that psoriasis is a disease of systemic inflammation with ramifications for multiple organ systems The exact etiology is not known It is thought to be an autoimmune disease mediated by T-Lymphocytes Genetic or environmental factors activate plasmacytod dendritic cells -> production of various pro-inflammatory cytokines ( e.g TNF alpha ,interferon , interleukin ) and several of these cytokines stimulate keratinocyte hyperproliferation starting a cycle of chronic inflammation Lack of lipid secretion by epidermal cells -leads to flaky and scaly skin Genetic association – multiple genetic susceptibility loci have been identified and familial occurrence is common ( 36 % of patients have a family h/o psoriasis )
Genetic predisposition Smoking Obesity Alcohol consumption Taking certain medications which can worsen or induce psoriasis include beta blockers , lithium , indomethacin , tetracyclines and synthetic anti-malarials.
Disease burden -Psoriasis for many people results in profound functional , psychological and social morbidity Strong association with metabolic syndrome It is also associated with COPD , NAFLD and coronary artery disease Increased risk of cardiovascular disease and diabetes A low but elevated risk of Non-Hodgkin’s lymphoma and cutaneous T cell lymphoma Inflammatory bowel disease particularly Crohn’s disease Venous thromboembolism Non-melanoma skin cancer Psychiatric illnesses – including depression ( prevalence of up to 60 % ) and anxiety Despite it considerable impact on QoL psoriasis is under diagnosed and under-treated.
Presentation-psoriasis is a clinical diagnosis examine the primary lesion (and whole skin ) other common areas including the scalp chronic plaque psoriasis is the most common variant lesions are multiple , b/l & symmetric-ask if the lesions are itchy , burning or painful ask for any precipitating factors like trauma ( which may produce Koebner phenomena – see below ) , infection ( e.g tonsillitis ) , drugs , stress and alcohol Koebner phenomena- an injury to skin such as cut , scrape , insect bite or sunburn acts as a trigger ie this is psoriasis arising in areas of cutaneous injury ( may take 7 days or more ) Auspitz sign – scratch and gentle removal of scales cause capillary bleeding Check nails -about 80 % of patients with psoriasis have nail involvement which includes
Pitting – small depressions on the nail surface
Onycholysis – distal nail seperation from the nail bed
Subingual hyperkeratosis
Oil spots – orange yellow spots below the nail plate Examine joints Inquire about family h/o psoriasis.
Chronic Plaque psoriasis –also known as psoriasis vulgaris well demarcated bright red plaques covered by adherent silvery white scales lesions elevated > than 1 cm most common type of psoriasis which which affects 85-90 % of patients can affect any body site , often symmetrically, especially the scalp and extensor elbows , knees and gluteal clefy are the most frequently affected areas Plaques are frequently pruritic.
Flexural or intertriginous –Well circumscribed minimally scaly , thin plaques localised to the skin folds for eg inframammary , axillary , groim, genital , natal cleft regions the skin may be moist , macerated , may have fissures which may be smelly , itchy or both.
Guttate psoriasis –teardrop lesions mostly on trunk often following infections for e.g sore throat associated with group B infection more common in children and adolescent adults affects fewer than 2 % people
Erythroderma –life threatening situation more than 90 % of the body is red infection drugs , systemic disease and corticosteroid withdrawal have been implicated
Palmopustural- present on hands and feet sterile pustules on a base of erythema and scale.
Generalised pustular psoriasis -rare form manifests as multiple uniform sterile pustules on the body often accompanied by fever often requires hospitalization as it can be life threatening.
Differentials -Chronic plaque psoriasis
 atopic dermatitis contact dermatitis lichen planus seborrhoeic dermatitis onychomycosis tinea corporis pityriasis rosea mycosis fungoide lupus erythematosus

Guttate psoriasis
 pityriasis rosea viral exanthems drug eruptions secondary syphilis

Erythrodermic psoriasis
 drug rash with eosinophilia systemic symptoms of Stevens Johnson syndrome

Generalised pustular psoriasis
 pyogenic infection vasculitis drug eruptions

Assess severity –at presentation before referral to evaluate efficacy of interventions

Several tools are available for e.g Psoriasis Area Severity Index ( PASI ), static physician/patient global assessment
The impact of any type of psoriasis on physical , psychological and social well being.
Co-morbidities –discuss risk factors for co-morbidities explain that they are at higher risk of hypertension , diabetes , obesity , hyperlipidemia , CVD than people without psoriasis use a validated assessment tool follow NICE guidance – how to manage those
Check for psoriatic arthritis –up to 30 % of patients with cutaneous psoriasis may also suffer with psoriatic arthritis it may take up to 7-12 yrs for Ps-ar to develop after the onset of cutaneous arthritis five forms pf psoriatic arthitis are known 
1 distal oligoarthritis ( 4 or less jts )
2 Rh-factor negative polyarthritis
3 arthritis mutilans
4 sacroilitis
5 ankylosing spondylitis

A common presentation is dactylitis -affects the distal jt in an asymmetric fashion with soft tissue swelling producing a sausage like digit 

A screening tool can be used for e.g the Psoriasis Epidemiological Screening Tool ( PEST )- find it under Links and Resources section.
Treatment -Psoriasis has no cure It is a relapsing -remitting disease that often improves with warmer weather and relapses during stressful events or in conjunction with infections For mild to moderate disease topical therapy is the standard.
Corticosteroids –well tolerated and effective – have an antiinflammatory effect and are efficacious initial therapy. Long term SEs are uncommon
Can be used in combinations fo e.g with salicylic acid or Calcipotriol.
Vitamin D3 analogues –Calcipotriol- a Vit D3 analogue is considered first line topical agent for plaque psoriasis. Regulates epidermal cell proliferation and differentiation as well as production and release of pro-inflammatory cytokines. Safe and efficacious
Combination products –Calcipotriol + betamethasone dipropionate has been shown to be more effective than monotherapy alone in a Cochrane review. The combination gel can be used OD is well tolerated ( not for use on face , genital areas and flexural areas )
Salicylic acid –Degrades the stratum corneum by dissolving intracellular components holding keratinocyte together
Topical calcineurin inhibitors –Available as tacrolimus ointment and pimecrolimus cream ( no FDA approval ) can be used as steroid-sparing agents for acute maintenance treatment of plaques on the face , genital or intertriginous areas.
Referral –there is diagnostic uncertainty OR psoriasis is severe or extensive OR psoriasis cannot be controlled with topical therapy OR acute guttate psoriasis requires phototherapy OR nail disease has a major functional / cosmetic impact OR psoriasis is having a major impact on a persons physical , psychological or social well being people with generalised pustular psoriasis or erythroderma should be referred immediately for same day specialist assessment and treatment refer to rheumatologist if psoriatic arthritis is suspected at any stage


British Association of Dermatology leaflet
National Psoriasis Foundation is a very valuable resource with information for patients and professionals
American Academy of Dermatology Psoriasis resource centre
American College of Rheumatology on psoriatic arthritis
Canadian Dermatology Association
PIL on guttate psoriasis
Psoriasis Epidemiological Screening Tool
Psoriasis Area Severity Index
Screening tool for psoriatic arthritis
A collection of screening tools from International  psoriasis council

  1. Assessment and management of psoriasis : summary of NICE guidance BMJ 2012 ;345 :e6712
    NICE Bites psoriasis via
  2. Psoriasis – Types , Causes and Medication  F.Z Zangeneh et al via
  3. Management of psoriasis as a systemic disease : what is the evidence British Journal of Dermatology Volume 182 , Issue 4 June 2019
    Guideline for the management of psoriasis Derm Net NZ via
  4. Current Medicine Psoriasis and its Management L Naysmith et al via
    NICE guideline on psoriasis via
  5. Stat Pearls Psoriasis NCBI Bookslef Pragya A Nair  , Talel Badri via
  6. Diagnosis and Management of Cutaneous Psoriasis: A Review Alisa Brandon et al Advances in Skin and Wound Care Vol 32 , No 2 via
  7. Diagnosis and management of psoriasis and psoriatic arthritis in adults – SIGN guideline October 2010
  8. Psoriasis: Diagnosis and Treatment Review by Melissa DeCapua November 2016
  9. Diagnosis and management of psoriasis Whan B Kim Can Fam Physician v.63 (4) ; 2017 Apr



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