Papules, Pustules & Crusts Flashcards
Papule lesions
Lesions of what skin condition?
Flea bite hypersensitivity (flea allergy dermatitis)
- pruritus, erthema, excoriation, self-induced alopecia + crusted papules
Papule lesions
Lesions of what skin condition?
Sarcoptic mange (scabies)
- intense pruritus, excoriation, crusts, self-induced alopecia + papules
Papule lesions
Miliary dermatitis - what causes it?
Crusted papular dermatitis - not a disease - is a cutaneous reaction assocaited with hypersensitivty disorder – allergies (e.g., flea bites dermatitis
Classifications (3) of pustules / crusts?
superficial pyoderma = primary bacterial
pemphigus foliaceus = primary autoimmune
subcorneal pustular dermatosis via fire ant sting = primary sterile
Pustules & crusts - Infectious class / SF pyodermas
What are the 3 clinical presentations of superficial pyoderma? What is the most common organism causing this condition in dogs?
1. Bacterial folliculitis (DOGS!!!)
2. Bacterial impetigo
3. Exfoliative superficial pyoderma
Bacterium: Staphylococcus pseudointermedius
-> Emerging bacterium = Staphylococcus schleiferi
Pustules & crusts - Infectious class / SF pyodermas
Transformation stages of bacterial folliculitis skin lesions?
Pustules & crusts - Infectious class / SF pyodermas
Characterisitcs of bacterial folliculitis in short-coated breeds?
- spontaneous alopecia –> multifocal, moth-eaten appearance
- trunk & extremities
- commonly mistaken for dermatophytosis -> differentiate b/c bacterial folluclitis lesions do NOT expand / coalesce!
Pustules & crusts - Infectious class / SF pyodermas
Pathogenesis of the pyoderma bacterial impetigo?
“Puppy pyoderma”
Staphylococci invades (typically the abdomen) -> produces exfoliative toxins -> pustules -> epidermal collarettes
Pustules & crusts - Infectious class / SF pyodermas
Pathogenesis of the pyoderma Exfoliative superficial pyoderma?
Staphylocci produce exfoliative toxins that separate the stratum corneum => large, expansive epidermal collarette
Staph pesudointermedius, staph schleiferi
Pustules & crusts - Infectious class / SF pyodermas
Where to sample for cytologic examination for bacterial folliculitis versus bacterial impetigo?
Bacterial folliculitis: beneath the crust
Bacterial impetigo: edge of the epidermal collarette
Cytology: degenerate neuts. w/ IC bacteria, + free-floating epid. cells
Pustules & crusts - Infectious class / SF pyodermas
What two pyoderma skin condition has a clinical diagnosis (instead of via cytology)?
- Bacterial folliculitis of short-coated breeds
- Exfoliative SF pyoderma
presence of bacteria in sample is usually scant
Pustules & crusts - Infectious class / SF pyodermas
What antibiotics should be avoided in treat staphylococci spp. in SF pyoderma, and why?
Pustules & crusts - Infectious class / SF pyodermas
Describe the oral/systemic ABX treatment plan for SF pyoderma cases.
- Cephalosporins (cephalexin) and potentiated amoxicllin (clavamox) = beta-lactamase resistant
- ABX course = at least 3 weeks OR 1 week beyond clinical resolution
- Reserve the use of fluroquinolones for non-responsive cases (underlying trigger; abx-resistance, etc.)
Pustules & crusts - Infectious class / SF pyodermas
Treatment for idiopathic recurrent pyoderma in dogs?
Proactive use of antimicrobial shampoos (1-2x/week)
Pustules & crusts - Infectious class / SF pyodermas
Which Staphylococcus is resistant to ALL beta-lactamase-resistance ABX?
What are MDR bacteria?
Methicillin-resistant Staphylococcus pseudointermedius (MRSP)
Multi-Drug-Resistant (MDR) bacteria = bacteria resistant ≥3 classes of ABX
Pustules & crusts - Autoimmune class / Pemphigus foliaceus
Pathogenesis of pemphigus foliaceus?
auto-antibodies target desmosomes in the SF epidermis
any breeds of cats/dogs; chows, GSD, akitas seem pre-disposed
Pustules & crusts - Autoimmune class / Pemphigus foliaceus
What is the classical lesion presentation of pemphigus foliaceus in dogs/cats? Where can other lesions be found?
Bilateral, symmetrical facial lesions.
Others / more chronic: inner and outer pinna; footpads
Pustules & crusts - Autoimmune class / Pemphigus foliaceus
Diagnostic methods (3) to rule out SF pyoderma from Pemphigus foliaceus? What samples to collect?
- Cytology!! -> if NO bacteria present, likely pemphigus foliaceus (in addition to clinical signs)
- Bacterial culture (take samples from intact pustules
- Biopsy (intact pustule > lesion WITH crust)
Pustules & crusts - Autoimmune class / Pemphigus foliaceus
What are the big, round structures?
Acantholytic keratinocytes
Keratinocytes = comprise the epidermis.
Acantholysis is the loss of cohesion between keratinocytes as a result of dissolution of intercellular connections, sometimes resulting in an intraepidermal vesicle. Acanthocyte is an old name for keratinocyte, and means “prickle cell,” referring to the desmosomal spines that normally connect the cells.
Pustules & crusts - Autoimmune class / Pemphigus foliaceus
Treatment plan for canine pemphigus foliaceus?
PO glucocorticoids (prednisone / prednisolone) + azathioprine
If signs do not resolve after 3 months of initial treatment, refer to veterinary dermatologist
Pustules & crusts - Autoimmune class / Pemphigus foliaceus
Treatment plan for feline pemphigus foliaceus?
PO glucocorticoids (prednisolone) + cyclosporine + chlorambucil
If signs do not resolve after 3 months of initial treatment, refer to veterinary dermatologist
Pustules & crusts - Autoimmune class / Pemphigus foliaceus
Why don’t cats tolerate azathioprine?
It causes myelosuppression
Pustules & crusts - Autoimmune class / Pemphigus foliaceus
Why are most dogs / cats with pemphigus foliaceus euthanized?
Dogs: poor repsonse to therapy, adverse effects of immunosuppresison
Cats: poor repsonse to therapy, adverse effects of steroids (diabetes mellitus; cutaneous atrophy -> skin tear)
