Crusting, scaling and papular lesions Flashcards
Papules
- Primary lesions
- Small solid elevation of skin <1cm
- Often erythematous
- May form crusts of serum, pus of blood
Pustules
- Small <1cm skin elevation filled with pus
- Often starts as papule
- Depth in epidermis varies
- Fragile, short lived
- Often see crusts/epidermal collarettes
Common causes of pustules and papules
Infections
Ectoparasites
Hypersensitivities
Autoimmune disease
Infectious causes of pustules and papule
○ Superficial bacterial pyoderma/folliculitis
Esp dog, horse
○ Dermatophytosis
Esp cat
○ Malassezia dermatitis
Dog
Ectoparasitic causes of pustules and papules
○ Fleas
Dog, cat
○ Surface mites
○ Burrowing mites
E.g. Sarcoptes
○ Demodicosis
Dog
Hypersensitivity causes of pustules and papules
○ Flea
Esp dog, cat
○ Environmental, food
Esp dogs, cats, horses
○ Insect bites
Esp horses, farm animals
Follicular lesions
Bacterial folliculitis
Demodicosis
Dermatophytosis
Lesion distribution considerations
Caudal/dorsal trunk (dog) = fleas
Ventral abdomen, pinnal margins, elbows, hocks (dog) = sarcoptic mange
Lesions affecting face/pinnae/head
□ Consider autoimmune?
Lesions at various stages of development
□ Pyoderma has various stages
□ Pemphigus has lesions come in waves all at same stage
Investigations to rule out differentials
- Cytology +/- bacterial culture
○ Bacteria/Malassezia infection
○ If acantholytic keratinocytes present likely pemphigus - Sample regarding ectoparasites
- Sample to rule out dermatophytosis
- If pemphigus is suspected
○ Clear secondary infection and biopsy - If no strong suspicion of pemphigus
○ Thorough ectoparasite control program
○ Treat to eliminate secondary problem
If no change - biopsy
If signs resolve but relapse - investigate underlying immunosuppressive disease
If lesions resolve but pruritus remains - investigate hypersensitivities
Scale
- Usually secondary lesion
- Rafts of immature keratinocytes with accumulate at skin surface
- Due to hyperkeratosis
- Caused by increased or disrupted epidermal turnover
- Loose or tightly adherent
- Form scurf when desquamate
Crust
- Almost ALWAYS a secondary lesion
- When exudates dry on skin surface
○ Serum pus or blood - Often also involves surface squames , hair, topical medications
- Associated with
○ Scaling
○ Pustular/papular
○ Ulcerative/erosive - Very non-specific finding
Common causes of scale and crusts
Infections
Parasites
Hypersensitivities
Nutritional deficiencies
Autoimmune disease
Neoplasia
Infectious causes of scale and crust
○ Bacterial
Pyoderma/folliculitis (dog, horse)
Dermatophilosis (farm, horse)
○ Fungal
Dermatophytosis (all but esp cattle, horse, cat)
Malassezia dermatitis (dog)
○ Viral
Viral papillomas (cattle, horse)
Occult sarcoids (horse)
Infectious causes of scale and crust
○ Bacterial
Pyoderma/folliculitis (dog, horse)
Dermatophilosis (farm, horse)
○ Fungal
Dermatophytosis (all but esp cattle, horse, cat)
Malassezia dermatitis (dog)
○ Viral
Viral papillomas (cattle, horse)
Occult sarcoids (horse)
Parasitic causes of scale and crusts
○ Ectoparasites
Fleas (dog, cat)
Lice (farm, horse)
Surface mites, esp Chorioptes (horse, cattle)
Cheyletiella (rabbit), Psoroptes (sheep, rabbit)
Burrowing mites, e.g. Sarcoptes (dog), Trixacarus (guinea pig), Cnemidocoptes (bird)
Demodicosis (dog, hamster)
○ Endoparasites (horse)
