Psoriasis Flashcards
what is psoriasis
Chronic autoimmune disease characterised by well-demarcated, erythematous, scaly plaques
Psoriasis precipitating factors
- Emotional stress
- Trauma (koebner phenomenon)
- Alcohol and smoking
- Infection - strep throat
- Drugs - β-blockers, lithium, anti malarial drugs, swift withdrawal of topical or systemic steroids (‘rebound’ psoriasis)
Psoriasis histological features
Parakeratotic stratum corneum
Absence of granular layer
Expanded prickle cell layer
Large capillaries in papillary dermis
Munro microabscesses (leukocytes) in stratum corneum
UV light implications in psoriasis
Can be used as treatment but can made psoriasis worse in 10% patients
Psoriasis pathophysiology
- Keratinocytes experience stress (environmental factors)
- They release factors to stimulate plasmacytoid DC (dermis)
- pDC produce IFN⍺, release cytokines
- pDC migrate to lymph nodes & activate Th cells
- Activated Th cells cause an inflammatory cascade in dermis
- Attraction of neutrophils in the keratin layer
- forms munro micro abscesses in stratum corneum
- This results in keratinocyte proliferation
- hyperkeratosis & parakeratotic stratum corneum
- expanded prickle cell layer (^ keratinocyte turnover)
- loss of granular cell layer (loss of normal maturation)
- Dermal fibroblasts also become involved
- this contributes to the inflammation
- this contributes to abnormal keratinocyte proliferation
Describe chronic plaque psoriasis
This is the commonest type and causes symmetrical plaques on the extensor surfaces of the limbs (knees + elbows), scalp and lower back
Describe the plaques in psoriasis
Plaques are palpable, red & scaly with well defined edges and a raised silvery scale
What is auspitz’s sign
removing scale reveals pin-point bleeding
What is koebner phenomenon
psoriasis that develops in an area of trauma e.g. scratches, burns, surgical trauma
What is guttate psoriasis - what causes it & how does it present
Multiple small, tear-drop shaped, erythematous plaques occur on the trunk after around 7-10 days of Streptococcal infection in young adults
Guttate psoriasis treatment
Usually self limiting
If regularly occurring (emollients, topical tar, phototherapy)
Scalp psoriasis treatment
- Olive oil
- Tar shampoos
- Coconut oil
- Dovobet scalp, enstillar foam
Flexural psoriasis - location & appearance
•Psoriasis in groin, axillae or inframammary areas
•Shiny, red, well-demarcated plaques
•Scale not a prominent feature
•Is colonised by candida infections
What can flexural psoriasis be misdiagnosed as
Can be confused with fungal infection or intertrigo (skin fold dermatitis)
Flexural psoriasis treatment
Mild topical steroid / antifungal preparations e.g. Trimovate® cream, Canesten HC® cream
What is palmoplantar psoriasis
Psoriasis on palms and/or soles
Presents with very thick hyperkeratosis & painful fissuring
Palmoplantar psoriasis treatment
– topical tar preparations
–salicylic acid
–topical steroids
–phototherapy
–systemic immunosupressants
Palmoplantar pustulosis - clinical features & risk factors
Sterile yellow pustules fading to brown macules (palms/ feet)
Strong association with cigarette smoking
What is erythrodermic psoriasis
Dermatological emergency with >90% of skin surface red & scaly that usually occurs in patients with known or deteriorating psoriasis.
Erythrodermic psoriasis aetiology
withdrawal of potent topical or systemic steroids, drug reactions, ultraviolet burns
Erythrodermic psoriasis presentation
> 90% of skin surface red
With systemic symptoms
Erythrodermic psoriasis complications
hypothermia, cardiogenic shock, dehydration, anaemia, hypoproteinaemia
Erythrodermic psoriasis treatment
fluid balance, bed rest, emollients, systemic immunosupressants
Pustular psoriasis clinical features
•Generalised
•Painful skin, fever, malaise
•Sterile pustules
