Psoriasis Flashcards
What is psoriasis?
a chronic immune mediated disease with sharply demarcated erythematous plaque with scale
why does it develop?
- Polygenic predisposition + environmental triggers
- 35-90% have a FH
what is the pathogenesis?
T-lymphocyte-driven disorder that is a response to an unidentified antigen:
trigger factor –> stressed keratinocytes –> activation of dermal dendritic cells (antigen presenting cells)–> they go to lymph nodes & presents uncertain antigen to naïve T cells –> differentiation to Thelper cells –> psoriasis dermis –> plaque formation
- interleukins & TNF alpha amplify inflammatory cascade, stimulate keratinocyte proliferation
- VEGF–> angiogenesis
- Neutrophils in acute, active, pustular disease
what are trigger factors that can active the antigen presenting cells?
- infections
- drugs
- trauma
- UV light
- smoking
what’s the histology?
- Hyperkeratosis – thickening of stratum corneum
- Neutrophils in stratum corneum
- Acanthosis (thickening of s.basale & s.spinosum) with elongated rete ridges
- Dilated dermal capillaries
- T cell infiltrations
on examination, you may see koebner phenomenon. What is this?
when lesions develop across injured area
on examination, you may see Woronoff’s ring. What is this?
blanched halo of uniform width surrounding psoriatic lesions
Describe chronic plaque psoriasis, and what the plaques look like
- symmetric, extensor surfaces
- pink–red, well-demarcated plaques, with a silver scale seen especially on extensor surfaces of the knees
Describe guttate psoriasis
- who does it usually occur in?
- what can it be triggered by?
- what is its’ outcome?
- children, adolescents
- can be triggered by viral or bacterial infections, esp strep throat
- may resolve or may trigger chronic psoriasis in susceptible individuals
Describe pustular psoriasis
- intense inflammation
- pustules not infected- are sterile collections of inflammatory cells
- sometimes systemic symptoms
what are some causes of pustular psoriasis?
- pregnancy
- rapid taper/stop steroids
- hypocalcaemia
- infection
what is a form of pustular psoriasis?
- palmoplantar psoriasis
- more common in smokers
Describe erythrodermic psoriasis
- ‘red man’ syndrome - >80% body surface area involved
- may be associated with malaise, pyrexia and circulatory disturbance
what is treatment for erythrodermic psoriasis?
- admit
- fluid balance
- bloods / IV access
- thick greasy ointment emollients
- if have to give topical steroids, give mildest ones (potent can turn it into pustular)
what does scalp psoriasis look like, and what can it lead to?
- looks like really bad dandruff
- can lead to alopecia at affected areas
Describe flexural/inverse psoriasis
- Less scale
- Can be triggered or superinfected by localised dermatophyte, candidal or bacterial infection – these are also differential diagnoses
