Key Diagnostics in Dermatology

Question 1

What history should be taken for diagnosing dermatological disease?

Answer 1

• chronology - age of onset, seasonality, progression or static
• severity
• effects of previous treatments

Question 2

What are some pieces of evidence that show a patient is pruritic?

Answer 2

• alopecia
• excoriations
• saliva staining
• broken hairs

Question 3

What is important for completely seeing extent of lesions?

Answer 3

clipping surrounding hair

Question 4

What are 5 parts of the dermatologic database?

Answer 4

1. skin scrape
2. trichogram
3. yeast evaluation - impression smears
4. fungal evaluation
5. cytology - ears, putules

varies with individual preferences and geographical location

Question 5

What equipment is used for skin scrapes? What are 4 keys to get a diagnostic sample?

Answer 5

10 scalpel blade (dull) or spatula + slide + mineral oil

1. clip hair or scrape hairless areas - hair contains normal scale that looks like skin, but parasites will likely not be found there
2. squeeze skin gently prior to scraping
3. scrape a sufficient area
4. scrape to the proper depth

Question 6

What is the purpose of kneading the skin prior to performing a skin scrape?

Answer 6

expresses follicle contents

Question 7

What is considered a proper amount of area to scrape?

Answer 7

depends on amount of scale/crust, usually around 1-3 cm^2

• wet scalpel with mineral oil to catch skin
• deep scraping = capillary hemorrhage

Question 8

Is a deep scrape necessary?

Answer 8

no - squeezing the skin prior to scraping significantly improves number of positive samples

• squeezing, acetate tape > deep scraping

Question 9

Acetate tape prep:

Answer 9

demodicosis

• place tape on sample area and roll/knead skin

Question 10

What is seen on this skin scrape?

Answer 10

follicular plugs - normal debris from follicles

• ensures kneading was done correctly!

Question 11

What is seen on this skin scrape?

Answer 11

• oil from skin, different weight than immersion oil
• blood in right corner (deep scrape?)

Question 12

What is seen on this skin scrape?

Answer 12

grease, balls of oil

Question 13

In what 3 ways is yeast evaluated for?

Answer 13

1. demonstrate organism - impression smear, cotton-tipped applicator swabs, skin scraping (claws)
2. culture
3. histopathology

(Malassezia)

Question 14

What area gives the best diagnostic sample in impression smears?

Answer 14

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

Question 15

What is the purpose of heat fixing skin scrapes and impression smears?

Answer 15

sticks oil to the slide to keep contents on

Question 16

Adhesive vs normal slides:

Answer 16

adhesive = more recovery

Question 17

How does preparing tape preps differ?

Answer 17

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

Question 18

How is a microscope correctly focused?

Answer 18

• right hand moves slide
• left hand on fine focus
• always move up and down

Question 19

What is seen on this slide?

Answer 19

pollen

Question 20

What is seen on this slide?

Answer 20

• mold spore
• dirt - mineral, decaying material

Question 21

What is seen on this slide?

Answer 21

environmental mold

Question 22

What is seen on this slide?

Answer 22

saprophytic mold - incidental, looks like a Trichuris egg, but it would be must larger at this magnification

Question 23

What is seen on this slide?

Answer 23

saprophytic hyphum - non-pathogenic, common in animals housed on hay

Question 24

What is seen on this slide?

Answer 24

Chonchiformibius (Simonsiella) - normal lip and oral cavity bacterium, indicative of licking (pruritic)

Question 25

What is a trichogram? How is it performed?

Answer 25

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

Question 26

What hairs work best for trichograms?

Answer 26

must be in anagen, where they are actively growing and harder to pull out

• Poodles - hair remains in anagen

Question 27

What 5 things can be examined in a trichogram?

Answer 27

1. distal ends for evidence of pruritus (fractured ends)
2. hair shafts for developmental defects
3. evidence of fungal infection
4. roots to determine growth phase (telogen vs. anagen)
5. root area and slide for ectoparasites

Question 28

Trichogram:

Answer 28

Question 29

What is Adamson’s fringe?

Answer 29

where hairs are typically broken off

• can be pulled from follicle

Question 30

Trichogram:

Answer 30

Demodex cat

• commonly found in hair follicles

Question 31

Trichogram:

Answer 31

mites + eggs

Question 32

What are 4 options for diagnosing Dermatophytosis?

Answer 32

1. Wood’s lamp (especially for cats)
2. KOH preparation
3. fungal culture - most definitive, best to send out
4. histopathology - skin biopsy, low sensitivity

Question 33

What diagnostic is always recommended for pruritic patients?

Answer 33

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