Introduction to Dermatological Diagnosis

Question 1

What is a primary lesion?

Answer 1

Appears quickly and then disappears rapidly
Can then go on to leave behind secondary lesions

Question 2

What is a secondary skin lesion?

Answer 2

Chronic and evolves from primary skin lesions

Question 3

How would you describe a macule?

Answer 3

Focal, Circumscribed, non palpable, change in colour, <1cm in diameter

Question 4

What is the pathogenesis of a macule?

Answer 4

Increased/ Decreased melanin production
erythema due to inflammation or local haemorrhage due to trauma

Question 5

What is the description of a papule?

Answer 5

Solid, elevated lesion <1cm in diameter
larger lesion is called a plaque

Question 6

What is the pathogenesis of a papule?

Answer 6

Localised Inflammatory infiltrate

Question 7

What is the description of a pustule?

Answer 7

Small circumscribed area within the epidermis filled with pus

Question 8

What is the pathogenesis of a pustule?

Answer 8

Neutrophillic infiltration and infectious in origin

Question 9

What is the description of a vesicle?

Answer 9

Sharp circumscribed area within or below the epidermis, filled with clear fluid

Question 10

What is the pathogenesis of a vesicle?

Answer 10

Fluid collection due to inflammation

Question 11

What is the description of a wheal?

Answer 11

Sharply circumscribed, raised, oedematous lesion, transient

Question 12

What is the pathogenesis of a wheal?

Answer 12

Subcut oedema

Question 13

What is the description of a nodule?

Answer 13

Circumscribed, solid raised lesion >1cm in diameter, extends into the deeper layers of the skin

Question 14

What is the description of an epidermal collarette?

Answer 14

Loose keratin flakes arranged in acircle

Question 15

What is the pathogenesis of an epidermal collarette?

Answer 15

Remnant of a pustule or vesicle

Question 16

What is the description of an erosion?

Answer 16

A shallow epidermal defect that does not penetrate the basal membrane- Heals without scarring

Question 17

What is the pathogenesis of an erosion?

Answer 17

Trauma or inflammation

Question 18

What is the description of an ulcer?

Answer 18

Break in the continuity of the epidermis with exposure of the underlying dermis, often heals with a scar

Question 19

What is the pathogenesis of an ulcer?

Answer 19

Severe trauma

Question 20

What is the pathogenesis of lichenification?

Answer 20

Chronci trauma

Question 21

What is the description of lichenification?

Answer 21

Thickening and hardening of the skin, Exaggerated superficial skin markings, often hyperpigmented

Question 22

When would you use a superficial skin scrape?

Answer 22

• Sarcoptes, Notoedres, Cheylitiella, Otodectes
• Scalpel blade used to scrape in the direction of hair growth
• Mineral oil is applied to skin to help collect material

Question 23

When would you use a deep skin scrape?

Answer 23

• Suspected demodicosis
• Must squeeze the skin to release mites from hair follicles
• Mineral oil applied to the scalpel blade
• Scrape in the direction of the hair until the capillary is bleeding

Question 24

When would you use an impression smear?

Answer 24

• Ear or skin cytology
• Cotton swab or slide pressed directly onto the lesion

Question 25

When would you use tape strips?

Answer 25

Useful to identify malassezia also- cocci, rods, cheyletiella

Question 26

What is woods lamp used to diagnose?

Answer 26

* Microsporum canis infection * 50% fluorescence * Lack of fluorescence doesn't rule it out so culture is needed

Question 27

How would you use a fungal culture?

Answer 27

* Sterile toothbrush used to accumulate hairs * Then applied to the culture medium * Evaluate daily for 2-3 weeks

Question 28

How would you do a trichogram?

Answer 28

Pluck hair and evaluate under a low power microscope also useful for alopecia

Question 29

What is a fine needle aspiration useful for?

Answer 29

* Useful for solitary lesions * sample depend son the exfoliating capcity of the lesion

Question 30

What is a biopsy used for?

Answer 30

* Punch biopsy/ wedhe excision can be used * site selection is important (take multiple samples)

Question 31

When would you use allergy testing?

Answer 31

Used in the diagnosis of atopic dermatitis - must suspect disesae based on the history, clinical signs and examination

Question 32

What is the difference between serum testing and intradermal testing?

Answer 32

Intradermal testing is considered to be the gold standard -discontinuation of steroid-containing medications is required

Question 33

When would you use an elimination diet?

Answer 33

* To confirm or eliminate food allergy dermatitis as a cause of pruritus * Single protein and carbohydrate source * Not previously fed * 6-8 week duration * then re-challenge

Question 34

When would you use an insect control trial?

Answer 34

* For insect hypersensitivity * Environmental and animal flea control