Feline immune-mediated skin disorders

Question 1

How frequent are immune-mediated and autoimmune skin diseases in cats

Answer 1

rare

Question 2

What are the two possible mechanisms explaining an autoimmune attack

Answer 2

Autoimmune attacks can be caused by:
- autoantiboodies (e.g., pemphigus foliaceus)
- autoreactive T lymphocytes (e.g., cutaneous lupus erythematosus)

Question 3

What characterizes pemphigus foliaceus

Answer 3

PF, which is considered the most common autoimmune skin disease in cats is characterized by erythematous acantholytic pustules, erosions and crusts that predominantly affect the face, nipples and feet

Question 4

What is the pathomechanism of pemphigus foliaceus

Answer 4

PF is characterized by the binding of pathogenic autoantibodies to desmosomal epidermal adhesion proteins, resulting in acantholysis and recruitment of inflammatory cells, with subsequent blistering of the superficial epidermis

Question 5

What would be your differentials for primary subcorneal pustules with acantholysis

Answer 5

Pemphigus foliaceus

Pustular dermatophytosis (e.g., Trichophyton)

Bullous impetigo (e.g., staphylococcal dermatitis with exfoliative toxins) (not described in cats)

Question 6

What is the typical cytologic appearance of PF

Answer 6

The classical cytology of PF lesions reveals the presence of acantholytic keratinocytes with variable numbers of well-preserved neutrophils and/or eosinophils

Question 7

What is the initial location of lesions in thymoma-associated exfoliative dermatitis

Answer 7

Skin lesions appear first on the head and pinnae, and then gradually progress to the back and trunck before generalizing
- these areas become progressively scaly
- alopecia develops as the exfoliation intensifies
- seborrheic, brown, waxy debris accumulate in the nail folds and between the digits

Question 8

What are the key features of auricular chondritis (“relapsing polychondritis”)

Answer 8

Auricular chondritis is a rare disease of cats characterized by inflammation and destruction of the auricular cartilage and occasionally non-articular cartilaginous structures

Pinnal lesions encompass swollen, thickening, deformation, pain and intense erythema
- the pinnae can also become violaceous in color and curl with chronicity
- most cases exhibit bilateral pinnal involvement

Median age of 3 years