Crusting, scaling, pustular & papular lesions

Question 1

What is a papule?

Answer 1

Small solid elevation of skin <1cm diameter
Often erythematous
May => crusts of serum, pus or blood

Question 2

Are papules primary or secondary lesions?

Answer 2

always primary

Question 3

What is a pustule?

Answer 3

Small (<1cm) skin elevation, filled with pus
Often start as papule
Depth in epidermis varies with the disease
Fragile, short-lived so often see as crusts/ epidermal collarettes

Question 4

Are pustules primary or secondary lesions?

Answer 4

always primary

Question 5

What are the common causes of pustules and papules

Answer 5

Infection
Ectoparasites
Hypersensitivities
Autoimmune disease

Question 6

Give examples of infections that cause pustules and papules

Answer 6

Superficial bacterial pyoderma/folliculitis – esp dog, horse
Dermatophytosis – esp cat
Malassezia dermatitis - dog

Question 7

Give examples of ectoparasitic causes of pustules and papules

Answer 7

Fleas – dog, cat
Surface mites
Burrowing mites, e.g. Sarcoptes
Demodicosis - dog

Question 8

Give examples of hypersensitivities that cause pustules and papules

Answer 8

Flea – esp dog, cat
Environmental, food – esp dogs, cats, horses
Insect bites – esp horses, farm animals

Question 9

Give an example of an autoimmune cause of pustules and papules

Answer 9

pemphigus foliaceus - dog and cat

Question 10

If pustules/papules are localised to the caudal/dorsal trunk of a dog, what is the most likely cause?

Answer 10

fleas

Question 11

If pustules/papules are located on the Ventral abdomen, pinnal margins, elbows, hocks (dog), what is the most likely cause?

Answer 11

sarcoptic mange

Question 12

If pustules/papules are follicular, what are the most likely causes?

Answer 12

bacterial folliculitis, demodicosis, dermatophytosis

Question 13

Describe the investigation and diagnostic steps involved in finding the cause of papules/pustules

Answer 13

Question 14

What is scale?

Answer 14

= Rafts of immature keratinocytes which accumulate at the skin surface

Due to hyperkeratosis (increased depth of cornified layer)

Question 15

What is the cause of scale?

Answer 15

increased or disrupted epidermal turnover

Question 16

Is scale a primary or secondary lesion?

Answer 16

Usually a secondary lesion, very occasionally primary

Question 17

What is crust?

Answer 17

When exudates (serum, pus or blood) dry on skin surface

Often also involves surface squames, hair, topical medications

Question 18

What are the possible causes of scale/crust?

Answer 18

infections
parasites
hypersensitivities
Nutritional deficiencies/metabolic diseases
autoimmune disease
Neoplasia
Primary keratinisation disorders (rare)

Question 19

Give examples of bacterial infections causing scale/crust

Answer 19

Pyoderma/folliculitis (dog, horse)
Dermatophilosis (farm, horse)

Question 20

Give examples of fungal infections that cause scale/crust

Answer 20

Dermatophytosis (all but esp cattle, horse, cat)
Malassezia dermatitis (dog)

Question 21

Give examples of viral infections that cause scale/crust

Answer 21

Viral papillomas (cattle, horse)
Occult sarcoids (horse)

Question 22

Give examples of ectoparasites that cause scale/crust

Answer 22

Fleas (dog, cat)
Lice (farm, horse)
Surface mites:
- Chorioptes (horse, cattle)
- Cheyletiella (rabbit)
- Psoroptes (sheep, rabbit)
Burrowing mites:
- Sarcoptes (dog)
- Trixacarus (guinea pig)
- Cnemidocoptes/scaley beak (bird)
Demodicosis (dog, hamster)

Question 23

in which species can scale/crust be caused by endoparasites?

Answer 23

horse

Question 24

Give examples of nutritional deficiencies/metabolic diseases that cause scale/crust

Answer 24

Photosensitisation (cattle, horse)
Hypothyroidism (dog)

Question 25

Give examples of autoimmune diseases that cause scale/crust

Answer 25

Pemphigus foliaceus Sebaceous adenitis

Question 26

Describe primary keratinisation disorders

Answer 26

Defects in normal keratinisation process: - abnormal formation of keratinocytes +/or - abnormal sebaceous gland function More common in younger animals

Question 27

Describe the process of diagnosing the cause of scale/crust

Answer 27