Dermatitis & Atopic Eczema Flashcards
what is hyperkeratosis?
increased thickness of keratin layer
what is parakeratosis?
persistence of nuclei in the keratin layer
what is acanthosis?
increased thickness of epidermis
what is papillomatosis?
irregular epithelial thickening
what is spongiosis?
oedema between keratinocytes
describe inflammatory cell infiltrate
can be acute or chronic infiltration of lymphocytes &/or neutrophils
what is dermatitis characterised by?
- itching
- usually ill defined
- erythematous
- scaly
what happens in the acute phase of eczema?
papulovesicular
erythematous lesions
spongiosis
scaling & crusting
what happens in the chronic phase of eczema?
lichenification
elevated plaques
increased scaling
describe the differences between the reactions in contact allergic and contact irritant dermatitis?
contact allergic = specific reaction
contact irritant = non-specific reaction
name some common contact allergic dermatitis triggers
nickel
substances in gloves e.g. latex
what are the pathological features of contact allergic dermatitis?
spongiosis
inflammatory cell infiltrate
how can specific substances causing contact dermatitis be identified?
through patch testing
what are the disadvantages of patch testing?
can’t shower/go to gym & can be uncomfortable to sit/sleep for 48 hours
when are patch tests checked & why?
taken off after 48 hours
checked after 96 hours as looking for delayed hypersensitivity
how is irritant (contact) dermatitis different to contact allergic dermatitis?
it’s a non-specific physical irritation rather than a specific allergic reaction
if a patient is atopic, are they more likely to have irritant (contact) dermatitis or contact allergic dermatitis?
contact allergic dermatitis
what are some common irritant dermatitis triggers?
- mechanical oils
- soap
- some metals
- licking lips (saliva)
what is nappy rash?
a non-specific irritant contact dermatitis in response to urine/faeces
what happens in flexures in atopic eczema?
is worse in flexures
what is generalised dry skin a manifestation of?
an abnormal skin barrier which lets water leak out & becomes dry
what chronic changes occur to the skin in atopic eczema?
lichenification
excoriation (crusting)
secondary infection
what does crusting of eczema indicate?
Staph. aureus infection
how is staph. aureus introduced into the eczema?
through scratching
what do monomorphic punched-out lesions leading away from eczema mean?
eczema herpeticum (herpes simplex virus)
what is the diagnostic criteria for atopic eczema?
itching plus 3 or more of:
- visible flexural rash (cheeks & extensor surfaces in infants)
- history of flexural rash
- personal history of atopy
- generally dry skin
- onset before 2 yrs old
how do you treat eczema?
- plenty of emollients
- avoid irritants
- topical steroids
- treat infection
- phototherapy (mainly UVB)
- systemic immunosuppressants
what causes atopic eczema?
multiple genetic & environmental factors
what is the most important gene in atopic eczema?
filaggrin
how can you recognise photosensitive eczema?
cut off at collar & no eczema in areas protected from sun (e.g. behind ears)
what is stasis eczema secondary to?
- hydrostatic pressure
- oedema
- red cell extravasation
what is cradle cap?
seborrhoeic dermatitis
what is lichen simplex caused by?
patient scratching and creating the eczema
