Pustules, ulcers and vesicles

Question 1

define pustules

Answer 1

small circumscribed pus filled elevation of the epidermis

• may be centred on hair follicles or interfollicular
• transient, often seen as crusts, epidermal collarettes or erosion

Question 2

causes of pustules

Answer 2

• pyoderma most common in dogs (rare in cats)
• sterile diseases less common in general eg. drug eruptions, pemphigous folaceous (most common in cats), subcorneal pustular dermatosis, sterile eosinophilic pustulosis

Question 3

Ddx pustules in dogs

Answer 3

• pyoderma (neutrophils and cocci)
• pemphigus folaceous (neutrophils and free epithelial cells)
• drug eruption (variable)
• subcorneal pustular dermatosis (neutrophils but no bacteria)
• sterile eosinophilic pustulossis (eosinophils)
• juvenile cellulitits (neutrophils and macrophages)

Question 4

Approach to pustules in dogs?

Answer 4

cytology
> if consistent with pyoderma, tx Abx and reexamine 10-20d
- skin scrap to r/o demodex
> if no response to Abx/cytology not consistnet
- culture and sesitivity for bacteria (suspect resistnace?)
- skin biopsies to dx all sterile pustular diseases

Question 5

Apporoach to pustules in cats and horses?

Answer 5

• biopsy all cases (v unusual in these spp)

- Abx tx pending results

Question 6

Ddx crusting in dogs and horses other than pustules?

Answer 6

• dermatophytes (dogs)

- dermatophilis congolensis (horses)

Question 7

Define ulceration. Causes?

Answer 7

• break in the continuity of the epidermis to expose underlying dermis
• consequence of self trauma w/ pruritis
• consequence of disease of epidermis/epidermo-dermal junction (infections/autoimmune/drug reactions/neoplasia)
• widespread may reflect progression from vesicles (intraepidermal vesicular dermatitides) and bullae (subepidermal vesicular dermatitides), epidermal separation (interface dermatitis) or epithelioptrophic lymphoma

Question 8

Prognosis of epithelioptrophic lymphoma?

Answer 8

• poor despite tx

- epidermis damaged by invasion of neoplastic lymphocytes

Question 9

Workup of ulcerative skin disease?

Answer 9

Biopsy routinely as may ddx severe and need aggressive tx

• intact 1* lesions best
• excisional biopsy across margins of lesions (if you only biopsy the ulcer, pathologist will tell you its an ulcer!)

Question 10

What are vesicles?

Answer 10

• fluid filled elevations of the skin LESS THAN 1cm in diameter (Bulla if >1cm)
• transient in haired skin due to thin epidermis
• histo: intra-epidermal/subepidermal vesicular dermatitis or interface dermatitis

Question 11

Aetiology of vesicles?

Answer 11

• viral
• irritant chemicals/burns
• auto-immune/immune mediated disease
  > NB: FMD notifiable in farm animals causes vesicles

Question 12

are drug reactions the same as drug side effects?

Answer 12

NO drug reactions immune mediated, drug side effects direct result of chemicals

Question 13

egs. drug reaction presentations

Answer 13

• urticaria and angioedema
• exfoliative erythroderma (red scaly skin)
• autoimmune presentation

Question 14

Dx drug reaction?

Answer 14

• hx drug exposure
• clinical signs of drug reaction
• histo
• r/o other causes
  > do not rechallenge with offedning drug!!!

Question 15

Tx drug reactions?

Answer 15

• stop offending drug
• suppotive/symptomatic tx
• mark in hx to ensure no future administration