Immune-mediated skin disease Flashcards
what is immune-mediated skin disease?
when the immune system fails to tolerate self-antigen and mounts an immune response to normal skin components
what causes primary immune-mediated skin disease?
idiopathic
what causes secondary immune-mediated skin disease?
trigger - toxin, drugs, bacteria, virus…
what are the key points to look for on an exam of a dog with suspected immune-mediated skin disease?
primary lesions
distribution of lesions
signalment/breed
what are the advantages of using cytology for immune-mediated skin disease?
easy, cheap, rapid
determines if sterile or not
determine type of inflammation
what are the two main sampling techniques used for cytology of immune-mediated skin disease?
direct impression smear
FNA
what lesions is direct impression smears useful for sampling?
pustules, exudative lesions (erosions/ulcers), draining tracts
what are skin biopsies and histopathology used for in immune-mediated skin disease cases?
getting a definitive diagnosis
what are the key points to remember when taking skin biopsies to use for immune-mediated skin disease diagnosis?
take at least three
sample primary lesions
sample range of lesions
sample entire lesion if possible
avoid erosions/ulcers
why are erosions/ulcers avoided when taking skin biopsies?
missing the epidermis so can’t diagnose anything that may be happening in this layer
what skin lesions can be seen in immune-mediated skin disease cases?
pustules
plaques/nodules
erythematous macules/patches
hypopigmented macule/patches
alopecia
vesicles
erosions/ulcers
crusts
purpura
scale
what are the main primary lesions seen with immune-mediated skin disease?
pustules
plaques/nodules
erythematous macules/patches
hypopigmented macule/patches
what are the least helpful lesions when trying to make a differential diagnosis for immune-mediated skin disease?
erosions, ulcers, crusts
what are crusts?
dried exudate on skins surface
what can crusts form from?
pus from pustules
exudate from ulcers/erosions
blood
what is the list of differentials for pustules?
bacterial infection (pyoderma)
pemphigus foliaceus
superficial pustular drug reaction
superficial pustular dermatophytosis
what are the two immune-mediated skin diseases that cause pustules?
pemphigus foliaceus
superficial pustular drug reactions
what is the lesion distribution for Memphis foliaceus?
footpads, pinnae, muzzle, ocular, lateral flanks
what disease are acantholytic keratinocytes seen with?
pemphigus foliaceus
why do we get acantholytic keratinocytes with pemphigus foliaceus?
auto-antibodies target desmosomes (these link the keratinocytes in the dermis) and hence the keratinocytes separate and become rounded
what do desmosomes do?
link keratinocytes in the dermis
what is the most common immune-mediated skin disease of dogs?
pemphigus foliaceus
in general how fast of an onset do immune mediated diseases have?
acute onset
what age dogs get eosinophilic furunculosis of the face?
young adults
is eosinophilic furunculosis of the face pruritic?
yes, very intense
what lesions are associated with eosinophilic furunculosis of the face?
eroded/ulcerated plaques and nodules