Derm - Crusting, ulceration, erosions, scale Flashcards
What are the causes of ulceration?
Trauma
Mechanical injuries
Acute moist dermatitis
Skin fold pyoderma
Thermal injuries
Chemical injuries
Radiation
Neoplasia
Infectious agenst
What is the prevalence of immune mediated skin disease?
Uncommon to rare
What are the causes of immune mediated skin disease?
Drugs
Neoplasia
Systemic disease
Other immune mechanisms
What should you consider when diagnosing immune mediated skin disease?
‘Interface dermatitis’ is not definitive
Consider underlying causes
How do you treat immune mediated skin disease?
Immunosupressive drugs
What is the prognosis of immune mediated skin disease?
Poor - Adverse effects of therapy, disease difficult to manage/treat
What are the attachments between epidermal basal cells called?
Desmosomes
What are the attachments between the basal cells and the lamina lucida called in the skin?
Hemidesmosomes
What disease attacks the desmosomes?
Pemphigus - immune system attacks the desmosome attachments
What dogs are affected with canine pemphigus foliaceus?
Any breed and any age of onset - most likely 2 to 7 years
What are the clinical signs of canine pemphigus foliaceus?
Chronic disease
Generalised skin lesions - face, pinnae, footpads, trunk
Cause pruritus
What lesions does canine pemphigus foliaceus cause?
Vesicles and pustules - rupture to form crusts and erosions
Scaling and alopecia
How do you diagnose canine pemphigus foliaceus?
Cytology of pustules
Skin biopsy using punch tool
What is found on cytology in canine pemphigus foliaceus?
Keratinocytes, neutrophils, sometimes eosinophils
No cocci - sterile pustules
However can get secondary infection so need to treat this before testing
What is the appearance of canine pemphigus foliaceus on histopath?
Intraepidermal and intrafollicular pustules with acantholytic keratinocytes in the granular or upper spinous cell layers
What is the most common autoimmune skin condition in cats?
Feline pemphigus foliaceus - not as common as in dogs tho
What are the clinical signs of feline pemphigus foliaceus?
Lesions on head, ears and nose, extending to rest of body
Claw beds have thick caseous green purulent discharge
What is a differential diagnosis of feline pemphigus foliaceus and how do you differentiate them?
Dermatophytosis - do a fungal culture which will come back negative
How do you diagnose feline pemphigus foliaceus?
Cytology of pustule - neutrophils with acantholytic keratinocytes
Skin biopsy for histopathology
Haematology - eosinophilia
How do you treat pemphigus?
Glucocorticoids - prednisolone - 2mg/kg/day until remission, then slowly reduce dose
What is the second most common autoimmune skin disease in dogs?
Canine discoid lupus erythematosus (facial DLE)
What are the clinical signs of facial DLE?
Photosensitive dermatosis of the top of the nose causing
Hypopigmentation
Erythema, scaling, erosions, ulcerations
Loss of normal architecture
What is the appearance of facial DLE on histopath?
Lichenoid lymphoplasmacytic interface pattern
How do you treat facial DLE?
Topical glucocorticoids
Topical tacrolimus - cyclosporin drug
UV protection - suncream
Vitamin E
What is an autoimmune skin condition/sydrome that affects horses?
Ulcerative pastern dermatitis
What are the clinical features of ulcerative pastern dermatitis?
Cellulitis, ulceration, crusting and oedema on the hind pasterns
Fissures
Excessive granulation tissue
Lameness
What are some contagious causes ulcerative pastern dermatitis?
Staph, dermatophilosis
Chorioptes
Dermatophytosis
What are some non contagious causes of ulcerative pastern dermatitis?
Photosensitisation
Vasculitis
Chronic progressive lymphoedema
How do you treat ulcerative pastern dermatitis?
Clip area - sedate
Medicated chlorhexidine shampoo
Analgesia
When do horses get alopecia?
Secondary to pruritus or folliculitis
What can cause equine pruritus?
Infectious causes - staph aureus
Parasites - flies, mites
Allergy
Photosensitisation
Contact reaction
What are the clinical signs of lice in horses?
Alopecia
Pruritus
Scale
How do you diagnose lice in horses?
They are visible to the naked eye - put rug on so warm, then remove and look
What are the different types of scale?
Most are dry, powdery, flaky keratin fragments
Some are waxy, greasy with a rancid odour
Disorder of what process is involved in scale formation?
Cornification
What are the steps of cornification?
Bundling of the keratin
Replacement of the cell membrane with a cornified envelope
Formation of lipid lamellar bilayers
Desquamation (exfoliation)
What does the cornified envelope do?
Makes the corneocytes resistant to being broken down
What is filaggrin?
Filaggrin aggregating protein - helps to aggregate the keratin filaments within the corneocyte
What enzyme helps to mediate the aggregation of keratin filaments?
Transglutaminase
What are in the stratum corneum?
A lipid rich matrix full of cells
Lamellar bodies containing lipid substrate
What are epidermal lipids derived from?
Keratinocytes and sebaceous glands
What can cause scale formation?
Abnormalities in epidermal cell turnover or keratin synthesis
What are primary keratinisation disorders? How common are they?
Breed related congenital diseases
Uncommon to rare
What are secondary/acquired keratinisation disorders?
Due to another underlying cause such as parasites, allergy, endocrinopathies etc.
Lot more common
What are some examples of primary keratinisation defects
Sebaceous adenitis
Idiopathic nasodigital hyperkeratosis
Lethal acrodermatitis
What is sebaceous adenitis?
When inflammatory infiltrate target sebaceous glands causing scaling
What is idiopathic nasodigital hyperkeratosis?
Excess keratinisation of the ears and pads of older dogs
What is lethal acrodermatitis?
A very rare bad disease affecting English bull terries fact, distal limbs and feet
What is ichthyosis?
A rare congenital disease causing large adhered flakes of scale on dogs (fish scale)
What breeds does ichthyosis affect?
Golden retrievers, jack russell terriers, american bulldogs
What causes ichthyosis?
Defects in the formation of the stratum corneum - increased stratum corneum production and decreased corneocytes desquamation - retention hyperkeratosis
What are the two types of ichthyosis?
Epidermolytic - suprabasal keratinocyte vacuolation due to mutation in epidermal keratins
Non epidermolytic - transglutaminase mutations and others
What is epidermolytic ichthyosis?
When the suprabasal keratinocytes become vacuolated due to mutations in the epidermal keratins
What are some examples of scale formation secondary to a defined underlying cause?
Inflammation
Allergy
Endocrine imbalances
Nutritional factors
What nutritional factors can cause scale formation?
Zinc
What are the two types of zinc nutritional disorders?
Type 1 - adult dogs eg. husky, malamute, samoyed that are unable to absorb zinc
Type 2 - Young growing large breed dogs that are growing too fast and not getting enough zinc in their diet
What are the clinical signs of zinc responsive dermatosis type 1?
Scaling, crusting, erythema and alopecia
Can be pruritic
Where does zinc responsive dermatosis type 1 affect?
Around the eyes, on the nose, ears and muzzle and around the mouth
On foot pads
How do you diagnose zinc responsive dermatosis type 1?
On clinical signs and seeing parakeratotic hyperkeratosis (have nuclei)
What animals can get zinc deficiencies?
Dogs - breeds or growing pups
Goats
Alpacas
What is a common sign of zinc deficiencies in goats and alpacas?
Scaling
How do you manage scaling disorders?
Address the underlying cause
Treat secondary microbial infections
Topical therapy
What topical therapy can you use on scaling disorders?
Medicines that slow down the production of corneocytes eg. salycyclic acid, a-hydroxyacids, glycerine
