2 - eczema Flashcards
how does acute eczema present?
- papulovesicular erythematous lesion
- very itchy
- ill-defined
- oedema/spongiosis reaction type
how does chronic eczema present?
- thickening/lichenification
- elevated plaques
- increased scaling
- excoriation (from picking/scratching)
what does histology of acute eczema look like?
- inflammatory infiltrates like lymphocytes in upper dermis
- fluid collections (looks like space around keratinocytes = spongiosis)
what is contact allergic dermatitis pathophysiology?
it’s a type IV delayed hypersensitivity, involves T cells reaction to external antigen like nickel, chemicals etc
- sensation stage = generates memory T cell after exposure to antigen (via langerhans cells in epidermis & MHC II)
- allergic stage = activation of sensitised Th cells in response to antigen releasing inflammatory cytokines
what investigation is done for contact allergic dermatitis?
patch testing = applying allergen directly to skin to try & produce allergic response (add Finn chamber patches that are filled with substance you’re testing)
what is contact irritant dermatitis?
non-allergic reaction to non specific physical irritation, just like a reaction to soap, water, cleaning products, nappy rash etc
what is atopic aczema?
= allergic reaction (to something like hay fever etc)
= very itchy, in 25% school age kids
what is pathophysiology of atopic eczema?
skin barrier impaired (genetic) + environmental + immunology
- skin barrier issue from mutation in filaggrin gene (which is aggregating protein that helps skin bind together) so gaps in skin so Th2 cells, dendritic cells & mast cells etc can all access easier and make allergic reaction
what are common areas for eczema in
a) infants
b) children
c) adults
a) extensor surfaces, face, scalp, nappy area
b) flexural surfaces
c) hand eczema most common
what is presentation of atopic dermatitis?
- ill defined erythema & scaling
- itch scratch scale
- generalised itch
- flexural distributions
- associated w other atopic conditions like asthma, allergic rhinitis, food allergy
- nodular pruigo (lichenification making itchy nodules, more in black people)
what is lichen simplex eczema?
physical trauma like scratching causing eczema
what is photo-induced/photosensitive eczema?
= reaction to UV light so on areas exposed to sun (like cut off collar rash - typical)
what is stasis (varicose) dermatitis?
= physical trauma to skin by increased hydrostatic pressure underneath
what is discoid eczema?
oval patches of eczema
what is seborrheic eczema?
cradle cap, oily patches on baby scalp - resolves w age
what is pompholyx/dyshidriotic eczema?
sudden acute flare eczema & spongiotic vesicles together make tiny blisters on palms & fingers & feet = very itchy
what is treatment of eczema?
- avoid irritants
- lots of emollients
- topical steroids
(betamethasone valerate 0.025% or clobetasone butyrate 0.05% if moderate. betamethasone valerate 0.1% if severe)
