layers of the skin
epidermis, dermis, and hypodermis (SQ)
layers of the epidermis
stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, stratum basale
parts of a complete dermatological exam
good lighting and magnification assess the skin- haired and non haired identify lesions- primary vs secondary which body sites are involved- lesions and distribution dermogram
primary lesions
initial eruption that develops spontaneously as a direct reflection of the underlying disease
appear and disappear quickly
secondary lesions
evolve from primary lesions or are artifacts induced by the patients or by external factors such as trauma/biting/licking/medication
usually stay around for a much longer time period
types of primary lesions
macule patch papule plaque vesicle bulla wheal nodule tumor cyst
types of primary or secondary lesions
alopecia scale crust follicular casts comedone pigmentary abnormalities
types of secondary lesions
epidermal collarette scar excoriation erosion ulcer fissure lichenification callus
macule
flat spot less than 1 cm on skin with change in skin color
patch
macule greater than 1cm
purpura, petechia, ecchymoses
type of macule caused by bleeding into the skin
papule
small, solid elevation in skin up to 1cm in diameter
plaque
coalition of papules forming flat topped elevation
pustule
small elevation of epidermis filled with pus
vesicle
elevation of epidermis filled with clear fluid
bulla
vesicle greater than 1cm in diameter
wheal
sharply delineated lesion of edama
nodule
solid raised palpable lesion greater than 1cm, can include abscess
tumor
large palpable mass- neoplastic enlargement
cyst
epithelial lined cavity with solid or fluid material
alopecia
absence of hair from area where it is normally present
scale
accumulation of loose fragments of horny layer of skin
crust
accumulation of dried serum, exudate on 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 bullae
scar
fibrous tissue has been replaced the damaged dermis or sq tissue
excoriation
linear abrasion of the skin
erosion
shallow ulcer that does not break basal layer
ulcer
break in epidermis with exposure of dermis
fissure
linear cleavage in the epidermis or dermis caused by disease or injury
lichenification
thickening and hardening of the skin
callus
a localized hyperplasia of the stratum corneum of the epidermis caused by pressure or friction. elbows and lateral hock areas are common sites for callus formation in the dog
superficial skin scrape
surface mites: sarcoptes, notoedres, otodectes, cheyletiella, demodex gatoi
moisten blade with liquid paraffin or KOH or mineral oil
scrape a large area because mites are fewer in number
if negative, does not rule out superficial mites
deep skin scrape
follicular parasites, mostly demodex
scrape small focal area with dulled blade using mineral oil
induce capillary hemorrhage
squeeze follicles
if negative, may not rule out follicular parasite
scrape multiple affected areas
put on glass side, 10x and lower condenser
anagen hair
ball or balloon
telogen hair
arrow head
tape impression smear
place scotch tape onto microscope slide after on skin
1 drop of #3 diff quick to slide
FNA technique
21-23 gauge needle
attached to 5ml syringe
put needle in lesion; aspirate; pull needle back and redirect into another site; aspirate
release pressure on needle before withdrawing
disconnect needle from syringe; add few mls of air to syringe and reattach needle
express contents in needle on to microscope slide
woods lamp
50% of m. canis strains will fluoresce
turn on lamp 5-10 minutes prior to use
false positives: keratin scale, soaps, dyes, and some medications
fungal culture
if hair shafts fluoresce via woods lamp, pluck those for innuculation. if nothing fluoresces, use sterile toothbrush technique
DTM- color changes occur, must look at every day
dermatophyte used protein in the media resulting in alkaline by products which turn media red at the same time dermatophyte colony appears. must check daily because non pathogenic fungi will use the protein source once carbohydrates are exhausted, but this type of colony would be present for days before the color change
skin biopsy indications
nodules/tumors, ulcers/vesicles, severe acute generalized disease, mucosal lesions, footpad lesions, lesions unresponsive to normal therapy
skin biopsy protocol
no prep, no scrub do not disturb lesion gently clip hair handle sample as little as possible place into formalin and culture pot can use punch, wedge, excisional, or amputation
bacterial culture and sensitivity
not indicated in all cases of bacterial pyodermas
indications: cytology shows cocci and rods or just rods, cocci but no response to correct antibiotic administered correctly, deep pyoderma, chronic AB/GC therapy, GSD pyoderma
sample techniques: swab, swab with surface prep, biopsy
allergy testing serology
rely on antigen specific antibody levels
no vet outlay, quick, no sedation or clipping required
no positive control, only detects circulating IgE, lab variations, false positives, grouped allergens, some false negatives
NOT reliable for food allergens
intradermal allergy testing
gold standard for identifying environmental allergens