Key Diagnostics in Dermatology Flashcards
What history should be taken for diagnosing dermatological disease?
- chronology - age of onset, seasonality, progression or static
- severity
- effects of previous treatments
What are some pieces of evidence that show a patient is pruritic?
- alopecia
- excoriations
- saliva staining
- broken hairs
What is important for completely seeing extent of lesions?
clipping surrounding hair
What are 5 parts of the dermatologic database?
- skin scrape
- trichogram
- yeast evaluation - impression smears
- fungal evaluation
- cytology - ears, putules
varies with individual preferences and geographical location
What equipment is used for skin scrapes? What are 4 keys to get a diagnostic sample?
10 scalpel blade (dull) or spatula + slide + mineral oil
- clip hair or scrape hairless areas - hair contains normal scale that looks like skin, but parasites will likely not be found there
- squeeze skin gently prior to scraping
- scrape a sufficient area
- scrape to the proper depth
What is the purpose of kneading the skin prior to performing a skin scrape?
expresses follicle contents
What is considered a proper amount of area to scrape?
depends on amount of scale/crust, usually around 1-3 cm^2
- wet scalpel with mineral oil to catch skin
- deep scraping = capillary hemorrhage
Is a deep scrape necessary?
no - squeezing the skin prior to scraping significantly improves number of positive samples
- squeezing, acetate tape > deep scraping
Acetate tape prep:
demodicosis
- place tape on sample area and roll/knead skin
What is seen on this skin scrape?
follicular plugs - normal debris from follicles
- ensures kneading was done correctly!
What is seen on this skin scrape?
- oil from skin, different weight than immersion oil
- blood in right corner (deep scrape?)
What is seen on this skin scrape?
grease, balls of oil
In what 3 ways is yeast evaluated for?
- demonstrate organism - impression smear, cotton-tipped applicator swabs, skin scraping (claws)
- culture
- histopathology
(Malassezia)
What area gives the best diagnostic sample in impression smears?
hairless areas give best skin contact (webbing is a good option)
- wear a glove on the hand holding the slide - fingerprints can make evaluating slide confusing
What is the purpose of heat fixing skin scrapes and impression smears?
sticks oil to the slide to keep contents on
Adhesive vs normal slides:
adhesive = more recovery
How does preparing tape preps differ?
no fixative (first step of Diff Quik) needed –> turns tape and adhesive slides white, making it hard to see and must wait 20 mins before it disappears
How is a microscope correctly focused?
- right hand moves slide
- left hand on fine focus
- always move up and down
What is seen on this slide?
pollen
What is seen on this slide?
- mold spore
- dirt - mineral, decaying material
What is seen on this slide?
environmental mold
What is seen on this slide?
saprophytic mold - incidental, looks like a Trichuris egg, but it would be must larger at this magnification
What is seen on this slide?
saprophytic hyphum - non-pathogenic, common in animals housed on hay
What is seen on this slide?
Chonchiformibius (Simonsiella) - normal lip and oral cavity bacterium, indicative of licking (pruritic)
What is a trichogram? How is it performed?
examination of hairs plucked from the patient
- firmly grasp hair with forceps
- gently remove hair (~12) from follicle
- place on a slide, line up in mineral oil
- add a cover slip
- examine under 4-40x
What hairs work best for trichograms?
must be in anagen, where they are actively growing and harder to pull out
- Poodles - hair remains in anagen
What 5 things can be examined in a trichogram?
- distal ends for evidence of pruritus (fractured ends)
- hair shafts for developmental defects
- evidence of fungal infection
- roots to determine growth phase (telogen vs. anagen)
- root area and slide for ectoparasites
Trichogram:
What is Adamson’s fringe?
where hairs are typically broken off
- can be pulled from follicle
Trichogram:
Demodex cat
- commonly found in hair follicles
Trichogram:
mites + eggs
What are 4 options for diagnosing Dermatophytosis?
- Wood’s lamp (especially for cats)
- KOH preparation
- fungal culture - most definitive, best to send out
- histopathology - skin biopsy, low sensitivity
What diagnostic is always recommended for pruritic patients?
fecal floatation - repeat 2-3 times
- Demodex spp, Sarcoptes canis, Cheyletiella spp can be found in floats due to patient licking them from the skin and swallowing them
