Papules, Pustules, Crust - Derm Flashcards
Flea bite hypersensitivity
Flea allergy dermatitis - papule lesion
Pruritus, erythema, excoriation, self induced alopecia are often seen w crusted papules
Sarcoptic mange
Scabies - papule lesion
Intense pruritus, exocoriation, crusts, self induced alopecia are often see w papules
Miliary dermatitis
Crusted papular dermatitis - papule lesion
Not a disease but cutaneous reaction pattern common w hypersensitivity in cats
Pustule vs crust
Pustule - small circumscribed elevation filled w pus
Crust - cellular debris, dried exudate/blood - left over dried up pustule, vesicle or bulla
Infectious pustule or crust
Bacterial**
Superficial pyoderma
autoimmune pustule or crust
Pemphigus foliaceus*
Sterile pustule or crust
Subcorneal pustular dermatosis - fire ant sting
Papule conditions
Flea bite hypersensitivity
Sarcoptic mange
Miliary dermatitis
Superficial pyoderma
Bacterial folliculitis, impetigo, exfoliative superficial pyoderma - all caused by staph Pseudintermedius (common) or schliferi (emerging)
Bacterial folliculitis
Extremely common in dogs, rare in cats
Affects follicles
Abdomen, groin, medial thighs, axillary - pruritus can be variable
Bacterial folliculitis lesion
Erythematous papules —>
Pustules —>
Crusts
Bacterial folliculitis in short coated dogs
EXTREMELY common
Skin lesions: Spontaneous alopecia, multi focal - will not expand or coalesce
Found on trunk & extremities
Pruritus is variable, can be mistaken as Dermatophytosis
Bacterial impetigo - pyoderma
Puppy pyoderma
Caused by strains of staph that produce exfoliative toxins - common in abdomen
Lesions: pustules, collarettes
exfoliative superficial pyoderma
Superficial spreading pyoderma - bacterial exfoliative toxins separate stratum corneum
Lesions:
Large readily expanding collarettes
Peripheral erythema
Hyperpigmented center of chronic lesion
PUSTULES ARE RARE, pruritus varies
Cytology for superficial pyoderma
Bacterial folliculitis
Bacterial folliculitis - sample from intact pustules & beneath the crust
Finding - degenerate neutrophils w intracellular bac
Cytology of bacterial folliculitis of short coat breeds
Cytology doesn’t yield degenerative neutrophils or bacteria - not reliable
Cytology for bacterial impetigo
Sample from intact pustules, edge of epidermal collarette
Findings - degenerate neutrophils w intracellular cocci, free floating epidermal cells due to separation of stratum corneum
Cytology of exfoliative superficial pyoderma
Sample from edge of epidermal collarette
Findings - similar bacteria to impetigo but presence is scarce
Treatment of superficial pyoderma a
Depends on location
Localized: topical antibacterials - chlorhexidine, benzoyl peroxide, dilute bleach, mupirocin, gentamicin, erythromycin
Oral/systemic antibiotics - cephalosporins, clindamycin, tetracyclines, sulfonamides, floroquinalones, rifampin, chorlamphenicol
Localized /topical antibiotics
Chlorhexidine (2-4%)
Benzoyl peroxide
Dilute bleach (1:100)
Mupirocin
Gentamicin
Erythromycin
Oral /systemic antibiotics
Cephalosporins
Clindamycin
Tetracyclines
Sulfonamides
Fluoroquinolones
Rifampin
Chloramphenicol
XX systemic antibiotics
Bacteria might not be suspectible
Staph = beta lactam, XX for penicillin, amoxicillin, ampicillin
Cephalosporins and potentiated amoxicillin are b lactamase resistant
Duration of treatment
At least 3 weeks, 1 week beyond clinical resolution
Floroquinalones - reserve for resistant infections
Combo therapy is ideal method
Treatment approach
Superficial pyoderma —> recurs after successful treatment —>investigate underlying causes
- allergic, parasitic, endocrine, chronic steroid use
- no cause = idiopathic recurrent pyoderma
TX for idiopathic recurrent pyoderma
- Frequent and proactive use of topical antibacterial shampoos and/or solutions
- Immunotherapy with bacterial extracts (i.e. Staphage lysate) – not available now
- Intermittent systemic antibiotic treatment – controversial treatment
Antibiotic resistant pyoderma
Lack of response + new lesions, spreading of old lesions, increased exudation
**time to perform a susceptibility test
MSRP
Methicillin resistance staph Pseudointermedius
Resistant to ALL beta lactamase resistance antibiotics
MDR
Multi drug resistant bacteria
Resistant to 3 or more classes of antibiotics
MSPR is not the same as MRSA
MRSA - methicillin resistant staph aureus
Normal flora in humans/horses NOT dogs = can be zoonotic pyodermas
Pemphigus foliaceus
Most common autoimmune skin disease in cats and dogs (horses)
Autoantibodies target desmosomes in superificial epidermis
Breeds predisposed to pemphigus foliaceus
Dogs - GSD, chows, akitas - could be any
Cats - any breed
Pathogenesis of pemphigus foliaceus
Autoantibodies
Neutrophils
Pustule + acantholytic keratinocytes
Erosion —> crust
progression of pemphigus foliaceus lesion
Pustules in irregular shape —> erosion—> crust, most common lesion at presentation
distribution of skin lesions in pemphigus foliaceus
Facial** bilaterally symmetrical
Nasal planum, nose bridge, periorbital, pinnae (convex or concave)
Feet
Generalized form
DX for pemphigus foliaceus
Cytology
Bacterial culture
Biopsy
Cytology findings for pemphigus foliaceus
nondegenerate neutrophils with acantholytic keratinocytes, no bacteria
Findings for bactieral culture for pemphigus foliaceus
to rule out superficial pyoderma (take samples from intact pustules)
Biopsy findings for pemphigus foliaceus
often diagnostic if appropriate samples taken (best = intact pustule, second best = lesion with crust, must include crust!)
Treating canine pemphigus foliaceus
Oral glucocorticoids - prednisolone /prednisone
If not improvement add Azathioprine - ADR: hepatotoxicity, Myelosuppression monitor
Can add cyclosporine
failed treatment of pemphigus foliaceus (+3months)
Time to refer to a dermatoplog
Treating feline pemphigus foliaceus
Oral glucocorticoids - prednisolone
Cats do NOT tolerate azathioprine - due to Myelosuppression
Failed +3 m poor prognosis
