Dermatitis Flashcards
aetiology of contact allergic dermatitis
in response to chemicals, perfume, nickel, latex, plants
presentation of contact allergic dermatitis (location, worse areas)
location - around the site of irritation
worse at thin skin
what is the immunological response in contact allergic dermatitis (5 steps and hypersensitivity type)
type IV hypersensitivity - delayed response
- Langerhans process antigen
- antigen passed on to T helper cells in dermis
- T helper cells take antigen to lymphatics
- antigen presented to other cells
- when antigen is encountered again = recognised = T cells proliferate and migrate to skin = dermatitis
what investigation would you do if you suspected contact allergic dermatitis
patch test
blood IgE
what is the difference between contact irritant dermatitis and contact allergic dermatitis
contact irritant dermatitis doesnt involve IgE (NOT an allergic response)
aetiology of contact irritant dermatitis
soap, detergents, cleaning products (eg under jewellery)
urine = nappy rash
lick lip dermatitis
aetiology of atopic eczema/atopic dermatitis
genetic (filaggrin mutation = filament aggregating protein)
environmental factors
what other conditions are associated with atopic eczema
asthma, rhinitis, food allergy
what age does eczema typical present
school aged children
what does atopic eczema look like on histology
spongiosis (white spaces in cells = looks like a sponge) and inflammatory infiltrate
NOTE - all other dermatitis have spongiosis on histology, but no inflammatory infiltrate
first line treatment of atopic eczema
emollients (eg e45) to soothe and hydrate
avoid irritants
second line treatment of atopic eczema (after emollients)
topical steroids
third line treatment of atopic eczema (after emollients and topical steroids)
treat infection
phototherapy
immunosuppressants
how does chronic eczema present
excoriations (scratch marks)
lichenification - thickening of skin bc of scratching
may be infected
how does staph aureus infected chronic eczema present
yellow crusting
aetiology discoid eczema
scratching of dry skin and irritation of skin
how does discoid eczema present
red plaques in well defined discs (DISCoid eczema)
can appear anywhere, unusual on face/scalp
what is pompholyx eczema associated with
oedema
how does photoinduced dermatitis present
stops at collar level
aetiology of lichen simplex dermatitis
scratch = itch cycle
location of lichen simplex dermatitis
back of neck, side of legs
aetiology of stasis dermatitis
hydrostatic pressure (eg oedema) = skin under pressure
what can stasis dermatitis predispose
venous leg ulcer
how do all dermatitis present on histology
spongiosis (white spaces in between cells = look slike a sponge)
what 2 infections are associated with dermatitis
herpes simplex virus infection
staph aureus infection
how does herpes simplex virus associated with dermatitis present
monomorphic punched out lesions
what does herpes simplex virus infection associated with dermatitis cause
eczema herpeticum
how does staph aureus infection associated with dermatitis present
yellow crusting
how does staph aureus manage to infect someone with dermatitis
scratching of skin = skin becomes broken
how is staph aureus infected dermatitis treated
PO flucloxacillin
hypersensitivity of contact allergic dermatitis
type IV hypersensitivity - delayed response
which cells process the antigen in contact allergic dermatitis
Langerhans
what is the role of T cells in contact allergic dermatitis
Langerhans pass on antigen to T helper cell
T helper cell takes antigen to lymphatics
why does the lymphatics take the antigen in contact allergic dermatitis
to present it to other cells
whenever any of them come in contact with it again = dermatitis occurs
which condition is filagrin associated with
atopic dermatitis/eczema
what is filagrin
filament aggregating protein
why doesnt everyone with filagrin get eczema
need skin barrier to be impaired
