Differential diagnosis & morphs

Question 1

List the differential diagnoses of a neutrophilic subcorneal pustule in dogs.

Answer 1

1) Impetigo.
2) Pemphigus foliaceus.
3) Pemphigus erythematosus.
4) Subcorneal pustular dermatosis (variable eosinophils also).

Question 2

Name a possible cause of subcorneal pustules in large animal species?

Answer 2

Dermatophilosis.

Question 3

Name a possible cause of subcorneal pustules in pigs?

Answer 3

Greasy pig disease (subcorneal vesicular-pustular).

Question 4

List possible differentials for follicular pustules

Answer 4

1) Pemphigus foliaceus (mural).
2) Idiopathic linear pustular acantholytic dermatosis (eosinophilic & neutrophilic; mural).
3) Leishmania.
4) Impetigo (neutrophilic).
5) Dermatophilosis (purulent; luminal folliculitis).

Question 5

List possible differentials associated with cytotoxic interface dermatitis

Answer 5

1) Chronic cutaenous lupus erythematosus.
2) Pemphigus erythematosus.
3) Epitheliotrophic T-cell lymphoma.
4) Fixed drug reaction.
5) Mucocutaenous lupus erythematosus.
6) Uveo-dermatologic syndrome/VKH like disease.
7) Ischemic dermatopathy/dermatomyositis.
8) Exfoliative cutaenous lupus of GSP.
9) Vesicular cutaenous lupus erythematosus of SS & collie.
10) Non-thymoma/thymoma-associated exfoliative dermatitis.
11) Intra-epidermal viral disease.
12) Lupoid onychitis.
13) Erythema ab igne.

Question 6

Name possible differentials of pan-epidermal cytotoxic dermatitis.

Answer 6

1) Staphylococcal toxic shock syndrome.
2) Proliferative necrotizing otitis externa of cats.
3) Epitheliotrophic T-cell lymphoma.
4) Erythema multiforme.
5) Stephen Johnson Syndrome.
6) Toxic epidermal necrolysis.
7) Thymoma- associated exfoliative dermatitis.
8) Graft vs host disease.
9) Intra-epidermal viral disease.
10) Superficial necrolytic dermatitis (potentially minor pattern).
11) Vitamin A responsive seborrehic dermatitis (potentially a minor pattern).

Question 7

List possible differentials associated with follicular cytotoxic dermatitis

Answer 7

1) Chronic lupus erythematosus.
2) Staphyloccocal toxic shock syndrome.
3) Proliferative lymphocytitic infiltrative mural folliculitis, dermatitis, apoptosis & parakeratosis in dogs (Labrador).
4) Epitheliotrophic T-cell lymphoma.
5) Exfoliative cutaneous lupus erythematosus of GSP.
6) Erythema multiforme.
7) Stephen Johnson syndrome.
8) Toxic epidermal necrolysis.
9) Intra-epidermal viral disease.
10) Graft vs host disease.
11) Pseudopelade.

Question 8

“Subcorneal or intragranular neutrophilic pustular dermatitis associated with superficial perivascular neutrophilic dermatitis & gram-positive cocci within pustule” Whats your diagnosis?

Answer 8

Impetigo.

Question 9

“Focal subcorneal neutrophilic pustular dermatitis associated with superficial neutrophilic perivascular dermatitis, lifting of SC & Gram-positive cocci with Dustan’s blue line” Whats you diagnosis?

Answer 9

Superficial spreading pyoderma now exfoliative superficial pyoderma

Question 10

Create a morph for cutaneous candidiasis.

Answer 10

Superficial neutrophilic pustular dermatitis associated with admixed perivascular dermatitis pseudohyphae/hyphae in superficial crusts/pustules

Question 11

What would be the morph for superficial spreading dermatophytosis?

Answer 11

Small superficial pustular epidermal dermatitis and mural folliculitis associated with admixed perivascular dermatitis and dermatophytic spores and hyphae within keratin

Question 12

“Severe broad neutrophilic subcorneal pustular dermatitis associated with acantholytic keratinocytes & secondary crusts” Would be the morph for what disease?

Answer 12

Pemphigus foliaceus.

Question 13

“Severe broad neutrophilic subcorneal pustular dermatitis & interface dermatitis associated with acantholytic keratinocytes &
secondary crusts” Would be the morph for what disease?

Answer 13

Pemphigus erythematosus.

Question 14

How would you describe “Canine Subcorneal Pustular Dermatosis?”

Answer 14

Subcorneal neutrophilic sterile pustular dermatitis associated with superficial neutrophilic perivascular dermatitis

Question 15

What species and breed would you associate a morph of “Broad subcorneal to panepidermal eosinophilic pustular dermatitis associated with moderate to severe superficial neutrophilic &
eosinophilic perivascular dermatitis, neutrophilic leukocytoclasia & vasculitis” with? What is the disease called?

Answer 15

Dog.
Miniature Schauzer.
Sterile superficial erythroderma of miniature Schauzers.

Question 16

You receive a morph of “Superficial pustular dermatitis associated with superficial neutrophilic & eosinophilic perivascular dermatitis, & dermal edema” from acute onset lesions. What should you do? Why?

Answer 16

Stop all drugs.
This is suggestive of a superficial drug reaction.

Question 17

What morph would be suggestive of Idiopathic linear pustular acantholytic dermatosis (ILPAD)

Answer 17

Eosinophilic and neutrophilic pustular dermatitis and mural folliculitis associated marked acantholytic keratinocytes and superficial eosinophilic dermatitis.

Question 18

The morph from the cow you biopsied last week states “ severe diffuse, chronic, intra-epidermal & follicular neutrophilic pustular dermatitis associated with layered crusts (or palisading crust) of parakeratosis, epidermal debris & degenerative neutrophils, epidermal hyperplasia”. What treatment do you implement & why?

Answer 18

Systemic oxytetracycline.
Dermatophilosis.

Question 19

Create a morph for Greasy Pig Disease.

Answer 19

Chronic moderate subcorneal vesicular to pustular dermatitis & suppurative luminal folliculitis associated with severe layered serocellular crusts (or palisading crust) with parakeratosis, severe dermal and epidermal edema with neutrophilic exocytosis (exudative) & neutrophilic perivascular dermatitis

Question 20

What morph could be compatible with Porcine juvenile pustular psoriasiform dermatitis?

Answer 20

Intracorneal & intraepidermal pustular dermatitis associated with moderate superficial diffuse eosinophilic & neutrophilic perivascular dermatitis, marked psoriasiform epidermal hyperplasia, & moderate parakeratotic-predominant hyperkeratosis (JPC)

Question 21

List the differential diagnoses for infiltrative mural folliculitis.

Answer 21

1) Dermatophytosis (lymphocytic; isthmus).

Question 22

What is the target of immune cells in feline pseudopelade?

Answer 22

Isthmus.

Question 23

Does pseudopelade involve sebaceous gland destruction?

Answer 23

No, only isthmus is targeted with infundibulae and sebaceous glands spared.

Question 24

What CD expressing cells are present perifollicularly in active feline pseudopelade lesions?

Answer 24

Predominance of CD3+, CD5+T-lymphocytes (75% of the cells) and CD1a-expressing dendritic antigen-presenting cells (25%). CD4 glycoprotein expressing cells(T-helper).