Approach to crusting

Question 1

What is the definition of crust?

Answer 1

*Collection of cellular debris, dried serum, pus or blood
*Primary lesion usually a pustule, vesicle or bulla

Question 2

Crust is usually a secondary lesion. When is this not the case?

Answer 2

*Zinc responsive dermatoses
*Vitamin responsive dermatoses
=crust form as a direct result of excessive scale from hyperkeratotic epithelium

Question 3

What are the 2 most common differential diagnoses of crusting from pustules?

Answer 3

*Superficial bacterial folliculitis
*Pemphigus foliaceus

Question 4

What are the most common differential diagnoses of crusting from erosions / ulcerations?

Answer 4

*Papulocrusted (miliary) dermatitis
*Deep microbial infections
*Erythema multiforme (crusting variable, can present with only erythematous macules/plaques)
*Vasculitis/vasculopathy
*Cutaneous/systemic lupus erythematosus (initial sign is loss of pigmentation)
*Feline cowpox virus infection
*German shepherd dog pyoderma

Question 5

If crust is due to self trauma in a pruritic animal what needs to be ruled out?

Answer 5

Ectoparasites

Question 6

How would you take a sample of crust?

Answer 6

*Try finding a primary lesion (pustule) to sample
*If not present lift crust + perform direct slide impression below the crust

Question 7

What and when does cowpox affect?

Answer 7

*Younger, hunting cats
*Infection in late summer

Question 8

What is the dermatological examination of cow pox?

Answer 8

• Initial crusted ulcer with distinctive crater-edge in some cases
• Generalised papular crusting 7-14 days later (following viral
  dissemination), may be hidden in coat
• Signs usually start around head, sometimes forefeet

Question 9

How is cow pox diagnosed?

Answer 9

PCR
BIOPSY

Question 10

How is cow pox treated?

Answer 10

Spontaneous recovery within 4-5 weeks unless immunocompromised - tx secondary infection

Question 11

What are some supportive therapy of cow pox in immunocompromised?

Answer 11

*Fluids
*Appetite stimulation
*Tube feeding if oral lesions

Question 12

What are the signs of a cutaneous calicivirus infection?

Answer 12

*Concurrent URT infection
*Crusted ulcers + vesicles on MM, lips + nose

Question 13

What are the clinical signs of feline herpesvirus ulcerative dermatitis?

Answer 13

*Facial lesions make a mask
*Crusted ulcer eyelids, muzzle + nose

Question 14

What can be used to treat feline herpesvirus?

Answer 14

ANTI-VIRAL THERAPY
-Famciclovir
-Lysine
-Feline interferon omega

Question 15

What is superficial necrolytic dermatitis a cutaneous marker for?

Answer 15

*Internal disease
*Underlying end-stage hepatic disease
*Pancreatic glucagoma

Question 16

What animals does superficial necrolytic dermatitis affect? What does it cause?

Answer 16

Old dogs - non-pruritic, pain + lameness if feet affected
Sites of trauma = footpads, mucocutaneous junction, muzzle + bony prominences

Question 17

How is superficial necrolytic dermatitis diagnosed?

Answer 17

Skin biopsy + Histopath
Haematology , biochemistry
Imaging - confirms hepatic disease

Question 18

How is superficial necrolytic dermatitis treated?

Answer 18

*Surgical if pancreatic neoplasia
*Nutritional management
*Corticosteroids can improve skin lesions

Question 19

What does mosquito-bite hypersensitivity affect? What does in cause?

Answer 19

*Affects outdoor cats during mosquito season
*Causes erythematous papules developing into crust, may have alopecia, depigmentation + ulceration

Question 20

What is Pemphigus foliaceus? What does it affect?

Answer 20

*Auto-immune skin disease
*Affect head + pinnae initially may spread to nipples + feet