Pigment, claws

Question 0

What is melanin formed by?

Answer 0

• melanocytes forming granules (melanosomes) in basal layer of epidermal structures
• transferred to keratinocytes and during anagen to hair matrix cells

Question 1

Which species particularly show pigmentation after inflamamtion?

Answer 1

westies, GSDs

Question 2

What 2 types of melanin exist?

Answer 2

- eumelanins 
> black
> insoluble
> oval melanosomes
> much researched
- phaeomelanins
> red/brown/yellow
> soluble in alkali
> round melanosomes
> little researched

Question 3

What is viteligo?

Answer 3

pigmentary loss as a consequence of autoimmune attack against melanocytes

Question 4

What is lentigo?

Answer 4

• macular melanosis
• mature dogs or young orange cats
• not clinically significant

Question 5

What is the most common cause of claw avulsion?

Answer 5

RTA

Question 6

What is paronychia? When is this seen?

Answer 6

• inflammation of the nail fold
• infection with bacteria or fungi (check immunosuppression)
• autoimmune (esp pemphigus folacious cats)

Question 7

What is symmetrical lupoid onchyodystrophy? Tx?

Answer 7

= lupoid onychitis 
- no uncommon
- sloughing clause 
- regrowth of brittle, cracked short claws
- multiple claws on multiple feet
- no skin disease elsewhere 
> histology: interface dermatitis
> Tx: amputation of P3, dew claws, trial therapy (oxytet/nicotimamide)

Question 8

What is a pustule?

Answer 8

• small circumscribed fluid-filled elevation of epidermis containing pus
• centred on follicles or interfollicular epidermis
• transient
• crusts, epidermal collarettes, erosions
  > pyoderma in dogs most common
  > some sterile inflammatory causes eg. drug reaction, pemphigus (esp cats), subcorneal pustular dermatosis, sterile eosinophilic pustulosis
  > pyoderma rare in cats

Question 9

How does approach to pustules in dogs differ to cats and horses?

Answer 9

• cytology of pustule contents sufficient in dogs
• if pyoderma: tx with Abx for staph, skin scrape to exclude demodex
• if not responsive to Abx or not pyoderma
  > culture for bacteria
  > skin biopsies (sterile pustular disease)
• cats and horses pustules rare
• biopsy all cases
• Abx tx

Question 10

What is ulceration

Answer 10

• break in continuity of the epidermis -> underlying dermis exposed

Question 11

Causes of ulceration

Answer 11

> self trauma
dermo-epidermal junction disease (infection, autoimmune, drug reactions, neoplasia)
widespread ulceration reflects:
- progression from vesicles and bullae (intra/subepidermal vesicular dermatitis)
- epidermal separation (severe interface dermatitis)
- epitheliotrophic lymphoma (poor prog despite tx)

Question 12

Diagnostics indicated for ulceration?

Answer 12

Biopsy

- many ddx need aggressive, potentially hazardous tx