Dermatology allergic and autoimmune Flashcards
Why are cats with fleas often the cause of dogs getting FAD
Because they can tolerate large burdens of fleas without showing signs
Signs of flea allergic dermatitis in dogs
Pruritis of caudal dorsum, medial thights
Signs of flea allergic dermatitis in cats
Pruritic miliary dermatitis of crusted papules, alopexia, head and neck greatly affected
What type of antibodies are associated wtih atopic dermatitis
IgE
Favrot’s criteria for atopic dermatitis
i) Early onset <3 years of age
ii) Indoor lifestyle
iii) Glucocorticoid responsive
iv) Pruritus sine materia at onset i.e itchy but nothing to see when it started THEN get changed associated with pruritis and scratching
v) Affected feet and/or ears
vi) Non-affected ear margins and/or dorsal lumbar [distinguish from FAD]
What must we remember to do in relatino to other diseases and Favrot’s criteria for atopic dermatitis
Treat other issues that are superimposed on top/mimic this condition e.g fleas, pyoderma
Then get a better specificity of the criteria
Infestation with what might give positive allergy testing to house dustmite
Sarcoptes scabei
How is atopic dermatitis treated basic
Steroids; should respond fully!! if not then suggests something else going on
How does intradermal skin testing work
Injecting antigen solution into skin; including positive (histamine) and negative control
Compare wheal size with positive control
Get a reaction where there is IgE cross linking and mast cell degranulatoin
What is atopic-like dermatitis
Where we have all the signs of atopic dermatitic but no evidence of an IgE response on intradermal skin testing or in-vitro allergen testing
Treatment options fo atopic dermatitis
Glucocorticoids
Calcineurin inhibitors (tacrolimus, ciclosporin)
Could do allergen specific immunotherapy
Shampoos
Janus kinase inhibitors e.g oclacitinib
Lokivetmab m-Ab against IL31 (cytopoint)
What is lokivetmab directed against
IL-31
Licensed for use in atopic dermatitis
When to go for allergen-specific immunotherapy and what are the success rates
Do it is the intradermal skin test allergy results make sense with lifestyle of animal etc
33% do very well, 33% have some improvement,, 33% no better
What is food induced atopic dermatitis/cutaneous adverse food reactions
= clinically very similar to atopic dermatitis but the reaction is triggered by food not external allergens
What is the classic signs of food induced atopic dermatitis
Any age
Classically non-seasonal pruritis
May see GI signs
What must we remember about in vitro allergen testing and food-induced atopic dermatitis
It is NOT reliable for this
How can we diagnose/treat food induced atopic dermatitis
strict diet trial for minimum of 1-2 months
What is feline atopic syndrome
variety of allergic diseases that may be associated with a hypersensitivity to environmental allergens and foods +/- FAD
Involves allergic dermatitis, asthma, GI disease
What cutaneous reaction patterns might a cat with feline atopic syndrome present with
1) Head and neck pruritis
2) Self-induced alopecia/hypotrichosis
3) Miliary dermatitis
4) Eosinophilic granuloma complex
Treatment for feline atopic syndrome
Systemic glucocorticoids and cyclosporins
Could try off licence oclacinitib
Options to deal with feline food allergy
- Can try hydrolysed diets
- Novel protein
WHat medication can cause contact dermatitis in cats
Otic medication
How common is allergic contact dermatitis in cats
Rare
Gets overdiagnosed
What drug can we use to spare steroids in feline atopic skin syndrome
Cyclosporine
Skin histopath with mast cells, lymphocytes and eosinophils may be indicative of what on a cat
Feline atopic skin syndrome
What drugs can we use to treat auto-immune skin disease
Immunsuppressive: Prednisolone, cyclosporine, azathioprine, chlorambucil, mycophenolate mofetil
Immunomodulating: tetracycline, niacinamide
Topical agent: tacrolimus
What topical drug might we use for autoimmune skin disease
Tacrolimus
WHat immunosuppressive drug should we not give to cats
Azathioprine
What is the new classification of autoimmune skin disease and which things fit under these groups
Antibody mediated AISDs: pemphigus/pemphigoid
Lymphocyte mediated AISDs: CLE
What are the three autoimmune diseases in the pemphigus group
Pemphigus foliaceous
Pemphigus erythematous
Pemphigus vulgaris
Signs of pemphigus foliacus
Pustules; Face and feet often worst affected + nail beds in cats; pustules etc
May see pyrexia, lymphadenopathy due to immune system activation
What is the aetiology of pemphigus foliaceus
Antibodies formed against desmosomes in stratum spinosum causing decoalescence to form pustules
Target antigens in pemphigus group dseases
Desmosome components which hold epidermal cells together
anti-desmogleins/desmo-collins
Which breeds are at increased risk of pemphigus foliaceous
Akita
Chow
What is the Tzanck test
Where a pustule is ruptured to do cytology
What might we see on cytology of a pustules with P foliaceous
Mature hypersegmented neutrophils with acantholytic cells (large and basophilic) which are from the stratum spinosum
Which epidermis layer is targeted in P foliaceous
Stratum spinosum
What medication can trigger p foliaceous in dogs
Spot ons
What does P erythematous look like and which animals are predisposed
Dogs, very rare in cats; GSDs, collies, shelties
Pupules/lesions limited to bridge of nose, eyes, ear pinnae
What is the most severe form of pemphigus
P vulgaris
How does pemphigus vulgaris PRESENT
Skin on axilla/ingiunum affected + mucocutaneous junctions, and MMs
Get haemorrhagic ulcerative crusting
Also see pyrexia, depression, halitosis
What happens in AISBD (bullous pemphigoid)
Formation of auto-antibodies against basement membrane causing separation of the dermis from the epidermis and bullae formation
Affects skin, mucocutaenous junctions and MMs; ulcerative
What other auto-immune disease does AISBD (bullous pemphigoid) resemble and how do we tell them apart
P vulgaris
Use biopsies
Treating AISBD
High dose preds + cyclosprone
Can add other immunosuppressives in if needing to reduce steroids
What is cutaneous lupus erythematosus
Lymphocyte rich dermatitis with prominent basal keratinocyte death
What is the most common form of cutaneous lupus erythematosus
Discoid lupus erythematosus
Signs of discoid lupus erythematosus
Nasal depigmentation, erythema, ulceration
What might we need biopsy to distinguish discoid lupus erythematosus from
Epitheliotrophic T cell lymphoma
Treatment of discoid lupus erythematosus
Avoid sunlight
If severe use immunosuppression
Try topical agents e.g tacrolimus
Can use immunomodulating effects of niacinamide if less severe
What does vesicular lupus erythematosus look like
Axillary and inguinal ulceration, alopecia and erytehma
Rare
Diagnosis of systemic lupus erythamtosus
Anti-nuclear antibody positive + anti-histone antibody positive
Biopsy of skin lesions can be helpful if they are rpesent
What signs might we see with systemic lupus erythematosus
half have skin lesions
Most have joint disease
Half have haematological changes due to bone marrow being targeted e.g anaemia, thrombocytopaenia, proteinuria
Some also show glomerulonephritis; would get marked proteinuria
How many biopsies should we take when assessing skin disease
Up to 6 probably; 1 not enough
Histology of atopic dermatitis
Superficial perivascular dermatitis with mast cells, eosinophils, lymphocytes and histiocytes
What type of hypersensitivity is allergic contact dermatitis
Type IV hypersensitvity mediated by cytotoxic CD8+ T lymphocytes
How is atopic dermatitis mediated
IgE response to environmental allergens
Because there is inflammation and IL4 production whcih causes shift from IgM to IgE
Histology of flea bite hypersensitity
Superficial perivascular eosinophilic, lymphocytic, histiocytic dermatitis
What is the target of pemphigus foliacus vs vulgaris (specifically)
P foliacus: desmoglein 1
P vulgaris: desmoglein 3; more present in mucocutnaeous junctions hence the clinical signs here
Histology of pemphigus
Superficial dermatitis with eosinophils, neutrophils, lymphocytes
Histology of discous lupus erythematosus
basal cell degeneration, infiltration of lymphocytes and plasma cells at the epidermal dermal interface (becomes very thick), with pigmentary incontinence (because melanocytes are in stratum basale and get damaged so release melanin and then macrophages phagocytose this) and crusting
Which dogs get bullous pemphigois most
Collies
HIstology of bullous pemphigoid
vesicles or bullae within basement membranes (between PM and stratum basale), eosinophils
On immunofluorescence see IgG etc at dermoepidermal junction
What immunosuppressive drugs could we use for autoimmune conditions
Prednisolone
Cyclosporine
Azathioprine (not in cats)
Mycophenolate mofetil
Chlorambucil
