Dermatology Introduction Flashcards
Layers of the skin
Stratum basale
Stratum spinosum
Stratum granulosum
Stratum lucidum
Stratum corneum
Primary derm lesion
Initial eruption develops spontaneously as a direct reflection of the underlying disease
appears quickly and disappears quickly
Secondary dermatology lesions
Evolve from primary lesions or are artefacts induced by external factors (trauma, licking and medication)
Usually stay around for a longer time period
Primary lesions
Macules, papules, pustules, vesicles, wheal, nodule, tumor, cyst
Primary or secondary skin lesions
Alopecia, scale, crust, follicular casts, comedo, pigmentary abnormalities
Secondary skin lesions
Epidermal collarette, scar, excoriation, erosion, fissure, lichenification, callus
Macule
Flat spot less than 1 cm on skin with change in skin color
Patch
Macule larger than 1 cm
Purpura, petechial, ecchymoses
Type of macule caused by bleeding into the skin
Papule
Small, solid elevation in skin up to 1 cm in diameter
Plaque
Coalition of papules forming flattopped elevation
Pustule
Small elevation of the epidermis filled with pus
Vesicle
Elevation of the epidermis filled with clear fluid
Bulla
Vesicle larger than 1 cm in diameter
Wheal
Sharply delineated lesion of edema
Nodule
Solid raised palpable lesion greater than 1 cm
Can include absecess
Cyst
Epithelial lined cavity with solid or fluid material
Alopecia
Hair loss
Scale
Accumulation of loose fragments of horny skin layer
Crust
Accumulation of dried serum, exudate on the surface of skin
Follicular casts
Accumulation of keratin and sebaceous material stuck to a hair shaft
Comedone
Dilated hair follicle filled with debris
Epidermal collarette
Scale arranged in circular pattern
Associated with pustule, vesicle or bulla
Scar
Fibrous tissue has replaced damaged dermis or s/c tissue
Excoriation
Linear abrasion of the skin
Erosion
Shallow ulcer that does not break the basal layer
Ulcer
Break in epidermis with exposure of dermis
Fissure
Linear cleavage (cracks) in the epidermis or dermis caused by disease or injury
Lichenification
Thickening and hardening of the skin
Callus
Localized hyperplasia of the stratum corenum of the epidermis caused by pressure or friction
elbows and lateral hock areas are common sites for callus formation in the dog
Superficial skin scrapes are used for
Finding skin mites
Sarcoptes, notoedres, otodectes, cheyletiella, demodex gatoi in cats
Performing a superficial skin scrape
Moisten blade with liquid paraffin or KOH or mineral oil
Scrape a larger area because mites can be few in number
If negative for a skin scrape, can you rule out mites?
No
Deep skin scrapes look for
Follicular parasites
Mostly demodex
How to perform a deep skin scrape
Scrape small focal area with a dulled blade using mineral oil
Induce capillary hemorrhage
Squeeze follicles
Put on a glass slide
10 x mucroscope and lower condenser
If a deep skin scrape is negative can you rule out follicular parasites
NO
Types of hair roots
Anagen hair = ball or balloon
Telogen = arrow head
What are you looking for in hair plucks
Ringworm
Follicle dysplasia
Surface parasites
What is a trichogram
A hair pluck/ analysis of hair root
Acetate tape impression smear
Scotch tape test
Place scotch tape onto microslide
Add 1 drop of #3 diff quick to slide
Looking to see bacteria, fungi and yeast
FNA technique
21-23 g needle
Attached to 5 ml syringe
Put needle in lesion and aspirate from two sites without pulling hte needle out
Disconnect needle, add air, reattch needle
Put contents on a needle
Will woods lamp always show a positive for a M. canis infection
No
Only 50% of M. canis strains produce tryptophan metabolites that fluoresce with UV light
How long should the Woods lamp be turned on before use
5-10 min
Can you have a false positive with a Woods lamp
Yes
Can be caused by keratin scale, soap, dye and medications
Which animals should recieve a fungal culture
ALL cats with skin disease
Dogs with inflammatory lesions
If the hair shaft is positive under Wood’s lamp, what is the next step
Plug hairs for DTM inoculation
If nothing fluoresces with a Woods lamp…
Use the sterile toothbrush technique
Comb pet with toothbrush to collect hair/scales used to inoculate media
DTM tests must be checked
EVERY DAY
Non pathogenic fungi will use the protein sources once carbohydrates are exhausted - causing it to turn red
Skin biopsy indications
Nodules/ tumors
Ulcers/ vesicles
Severe acute generalised disease
Mucosal lesions
Footpad lesions
Lesions unresponsive to normal therapy
Skin biopsy steps
No prep or scrub
Do not disturb lesions
Gently clip hair
Handle the sample as little as possible
Place into formalin and culture
Types of skin biopsy techniques
Punch biopsy
Wedge/ excisional biopsy
Amputation- nail or toe
Indications for bacterial culture and sensitivity
Cytology shows cocci and rods or just rods
Cocci but no response to the right antibiotics given at the right time
Deep pyoderma
Chrinic antibody and glucocorticoid therapy
GSD pyoderma
Gold standard test for environmental allergens
Intradermal allergy testing
Allergy testing with Serology advantages
No vet outlay
Quick
No sedation or clipping required
Disadvantages of allergy testing
No positive control
Only detects circulating IgE
Lab variations
False positives
Grouped allergens/ limited
Can have false negatives
Not reliable for food allergens
