Derm Fundamentals Flashcards
What does skin do
1) Barrier- keeps moisture, protein, and electrolytes in
2) Keeps microbes and allergens out
3) Largest organ in body
4) Innate and adaptive immunity
what is the vascular portion of the skin
the dermis
Why is dermatology really important
9 in cats - atopic dermatitis
Top 4 reasons (dogs)
1) Atopic dermatitis
2) Ear infections
3) Benign skin neoplasia
4) Pyoderma
10) Anal gland sacculitis/expression
You should never say that something smells
yeasty
What is important to distinguish when getting the history
1) Need chronological order
2) Which came first, lesions, or itch
3) Disease progression
4) Prior treatments, efficacy
5) Seasonality
What might be affecting younger patients
think things that would affect an immature immune system
-Infection- impetigo (superficial non-follicular bacterial infection)
-Ectoparasitism- Demodex, ear mites, fleas, scabies
-Congenital/genetic- ichyhyosis (goldens), dermatomyositis (collies)
-Food allergy
What breed commonly gets ichthyosis
goldens
What breeds commonly get dermatomyositis
collies
What dermatological issues do you think of with older patients
1) Endocrinopathy (Cushings)
2) Neoplasia (epitheliotropic lymhoma)
3) Organ failure (superficial necrolytic dermatitis)
What is it called when a puppy develops a superficial non-follicular pyoderma
Impetigo
What kind of dermatologic conditions should you consider for middle aged dogs
anything
condition where liver failure can lead to dermatological conditions
Superficial necrolytic dermatitis
What breeds are predisposed to sebaceous adenitis
Poodles and Akitas
How can sex influence your work up of dermatological diseases
intact male? possible sertoli cell tumor leading to sex hormone dermatoses
What behaviors indicate pruritus
scratching
licking
chewing
biting
rubbing
If the prurutus is primary on the caudal dorsum, what does this make you think
flea bite hypersensitivity
If the pruritus is primarily across the entire body and trunk you think
lice/cheyletiella
If the pruritus is on the ventrum, paws, mouth, and eyes you think
allergic dermatitis (environmental/food)
Types of primary dermatololgic lesion
Papula
Nodule
Pustule
Bulla
Vesicle
Comedone
Macules
Plaque
Nodule
Are primary or secondary lesions more diagnostic
primary- they come first
What are examples of secondary lesions
Alopecia
Crust
Collarette
Lichenification
Seborrhea
Excoriation
Erosion
Ulcer
Fissure
Hyperpigmentation
Leukotrichia
thinning of the hair
hypotrichosis
complete hair loss
alopecia
What are words to describe lesion configuration
1) Linear
2) Reticular (net-like)
3) Punctate
4) Patchy
5) Well-circumscribed
6) Diffuse
Words to describe color and texture of lesions
soft
purulent
fluctuant
exudative
erythematous
dry
moist
net-like lesion configuration
Reticular
reddening of the skin
erythematous
Macules are ________
Patches are ________
Macules <1cm
Patches >1cm
flat area of different color < 1cm >
-erythema
-hyperpigmentation
-purpura (dermal bleeding)
-petechiation (dermal bleeding, punctate macules)
-Ecchymoses (dermal bleeding, patch)
Macule/Patch
Erythema is most likely due to
vasodilation (inflammation) or hemorrhage
Hyperpigmentation is most likely due to
inflammation (post-inflammatory)
Why is it important to do diascopy
press on the lesion with a slide to see if it blances
Vasodilation if it blanches bc youre squishing vessels
Hemorrhage if it stays (vasculitis?)
Dome-shaped
solid
raised area
often confused for hives/urticaria
<1cm
Papule
(hives are transient but papules stay forever)
What should you do for pustules
Cytology!
-often suggestive of follicular disease but not always -pyoderma (infection)
Pustules are often suggestive of
-often suggestive of follicular disease but not always -pyoderma (infection)
Papules are _______
Nodules are ______
both are raised solid dome shaped structures
Papules <1cm
Nodule >1cm
dome shaped
solid
raised area
often dermal/SQ
>1cm
ulceration and drainage occur in many causes
Nodule
a raised but flat on top nodule
solid
plaque
Vesicles are ________ while bulla is ______
Vesicles <1cm
Bulla >1cm
Vesicles and bulla are usually
immune mediated
epidermal collarette usually starts as a
papule/pustule and then extends outward
What typically causes epidermal collarettes
Infectious
-Bacteria
-Dematophyte
-Demodex
annular
crust
erythema
hyperpigmentation
well circumscribed
starts as a papule/pustule and extends outward
Epidermal collarette
What is another term for hives / wheals
urticaria
well circumscribed edema
raised area
type I hypersensitivity
confused for collarettes but no crust
Wheal / Urtucaria / Hive
What causes wheal / urticaria
type I hypersensitivity
horses: exercise and stress
people: cold temps
How do you distinguish wheals from collarettes
no crust with wheals
wheals go away quickly
partial alopecia
can be traumatic (fractured hairs) or true absence of the hair shaft)
hypotrichosis
Anytime we have hair loss, what should we ask
Is it falling out or being removed (pruritus) ?
Is it growing back (endocrine)?
seborrhea sicca
dry form of scale “dandriff”
exfoliation problem
epidermis- stratum corneum
seborrhea oleosa
greasy form of scale
exfoliation problem
epidermis- stratum corneum
What often causes scales (seborrhea sicca and oleosa)
allergy
steroids
infection
What is follicular casting
severe seborrhea sicca
“cast” = shape of follicle
typically associated with sebaceous adenitis (immune)
What is follicular casting typically associated with
sebaceous adenitis (immune)
thickened stratum corneum
scale that is not exfoliated
hyperkeratosis
What are the two types of hyperkeratosis that is only distinguishable on histopathology
Thickened straum corneum
1) Orthokeratotic = non-nucleated
2) Parakeratotic = nucleated
hyperkeratosis where the stratum corneum is non-nucleated
orthokeratotic
hyperkeratosis where the stratum corneum is nucleated
parakeratotic
follicles that become plugged up with sebum
“blackheads”
caused by demodex, acne, endocrinopathy
Comedones
With comedones, the follicles become plugged up with
Sebum
What causes Comedones
1) Demodex
2) Acne
3) Endocrinopathy (ie hyperadrenocorticism)
a reaction pattern that is typically chronic inflammation and macroscopic
thickened, wrinkly, elephant skin,
often hyperpigmented
lichenification
What causes lichenification
Chronic inflammation- reaction
-allergic dermatitis
-hypothyroidism
-Malassezia (yeast) dermatitis
a dry exudate that is secondary to erosion / ulceration
-Hemorrhagic
-Purulent
-Serous
Not scabs
Crust
How do scabs differ from crusts
Crusts are a dried exudate (blood, pus, serum) while scabs are fibrin deposit for body and solving a problem
Whats the difference of erosion to ulcer
Erosion- partial absence of epidermis
Ulcer- complete absence of epidermis
partial absence of the epidermis
due to: trauma, deep pyoderma, immune-mediated disease
Erosion
complete absence of epidermis
due to: trauma, deep pyoderma, immune-mediated disease
ulcer
linear ulceration
fissure
What might cause pigmentation issues of skin
reaction pattern (chronic)
-Immune Mediated disease (hypo)
-Allergic dermatitis
-Mucocutaneous pyoderma
-Vitiligo
-Hypothyroidism
What should jump to your mind when you see complete loss of pigmentation
1) Immune mediated disease -Discoud lupus, vitiligo
2) Neoplasia - epithelial trochlear lymphoma
If you have a patient that is really itchy, what should you consider
Sarcoptes scabei
How do you search for fleas
Flea comb - to look for fleas or flea dirt
use a wet q-tip to moisten the dirt with water or alcohol to show the owner that it is blood and debris
harder on cats because they groom regularly
What other ectoparasite can you use a comb to detect
Cheyletiella - then look undermicroscope
T/F: sarcoptes scabei is zoonotic
true
what might increase your chance of finding mites
sample from locations where the animal cant groom very well
ie behind pinna
mite that commonly affects the ears of camels and sheep
Psoroptes ovis
What mites are detectable with superficial skin scapes
-Sarcoptes scabei
-Psoroptes ovis
-Cheyletiella
when doing a superficial skin scrape, why should you not get blood
because mites living in stratum corneum and sometimes in the superficial epidermis
What do you need for skin scrapings
-Blade or spatula
-Mineral oil
-Slide and coverslip
1) Trim long hair w scissors - keep crusts
2) Mineral oil on blade to help collect debris
3) sweep the blade- superficially like butter bread
4) Smear on the slide
What species of mite can you do tape prep on
Cheyletiella
Where do demodex species like to live
deep in the hair follicle and sebaceous glands
For Demodex spp you do deep skin scraping except ofr
Feline Demodex - lives on the superficial skin and causes pruritus in cats - do superficial skin scrapes
How do you know when youve achieved a deep skin scrape
there is a little bit of capillary bleeding
indirection of hair growth
What direction to do stroke when doing a deep skin scrape
in the direction of the hair growth
What can you do in hard to scrape areas for Demodex
hair plug- paws or around eye
but keep in might it is not as sensitive as DSS
Is hair pluck or deep skin scrape more sensitive for demodex
Deep skin scrape
How do you analyze a deep skin scrape on the miscropscope
View at 5x or 10x objective - lower condenser
Demodex- record location scraped, # adults, eggs, juveniles
you should heat fix when the lesion is
waxy
acetate tape cytology is important for
rapid assessment malassezia, cocci, rods
feet, periocular areas
lots of debris but it is an acquired skill
T/F: you cant stain acetate tape cytology
False
What are microscope tips for cytology
1) raise condenser
2) Start out on 5x then 10x
3) Look for clumps of blue and purple
4) then use immersion oil and 100x for identification and quant
What are methods to diagnose dermatophytosis
1) Wood’s lamp: 40% of M. canis
2) Trichogram
3) Dermatophyte PCR
fungal culture* is gold standard
With dermatophytosis, what would you see on a trichogram
a hair with no definition between cortex and medulla
spores adhered to hairshaft
When doing a Wood’s lamp for dermatophytosis dx, what do you need to consider
the actual hair shaft is fluorescing
crusts, medications, debris will all fluoresce
How do you collect a sample for dermatophytosis fungal culture
1) Wipe hair with alcohol to discourage saphrophytes
2) Pluck from periphery because that is where the active dermatophytes
What does dermatophyte growth look like when culturing
colonies should be white and fluffy (M. canis)
media turns red when dermatophyte growth
go further to find he species - color change with beige/white growth
How do you identify dermatophyte down to species level
slide with lactophenate cotton blue
see dermatophyte macroconidia
You will only see dermatophyte macroconidia when
you take a sample from the culture plate
It is not a phase that grows on the patient
How do you prepare for skin biopsy
1) Local anesthesia: lidocaine/ bupivacaine SQ application (0.5-1ml/site)
+/- deep sedation or anesthesia for feet and face
Do NOT surgically prep/scrub the area
What are typical biopsy punch sizes used
8mm or 6mm
small-4mm for planum nasale
When doing punch biopsies why should you only twist in one direction
can create a shear artifact which can give separation of dermis from epidermis
You should never biopsy
Ulcers- you need intact epidermis to diagnose disease processes
How many punch biopsies should you take
At least 3 that are representative- may be many types
get as big and as many as you can
Should you do junctional biopsies
avoid if possible - you want to take all abnormal site
exception: widestream ulcer, not much healthy tissue to sample
How do you show the pathologies the direction of hair growth
grow a line in the direction of the hairgrowth
this allows pathologist to know how to cut the tissue so they do not get cross sections
