45. Allergodermatitis (without atopy) Flashcards
Recommended order to perform dermatological exam?
Aetiological classification of skin diseases?
AETIOLOGICAL CLASSIFICATION OF SKIN DISEASE
§ Congenital § Allergic
§ Bacterial § Fungal
§ Normergic dermatitis § Neoplastic
§ Autoimmune § Endocrine
§ Ectoparasitic § Other
Atopic dermatitis?
Allergodermatitis (Without Atopy)
It is important to treat more than just the allergy, especially in atopic dermatitis where pyoderma is severe and must also be treated.
ATOPIC DERMATITIS
Eczema
The most common type within the allergies
Long-term-type of inflammation of the skin: Itchy, red, swollen &
cracked skin
Diagnosis: Step by step exclusion diagnosis
Adverse food reaction?
ADVERSE FOOD REACTION
20% of cases; One or more proteins in food provokes allergies
Type-1, type-2 or type-4 hypersensitivity reactions caused by beef, fish, milk etc.
Clinical signs
May be accompanied by GI signs
Dog: Pruritis; Seborrhoea; Urticaria
Cat: Generalised pruritis; Miliary dermatitis-like lesions; Facial dermatitis; Eosinophil plaque/granuloma
Diagnosis
Elimination trial
§ Only give one protein at a time to work out which is the
cause of the allergy
§ Perform the feed trial for 2 months
§ If the patient is still pruritic, suspect atopic dermatitis
IgE testing
Id-testing
Treatment: Allergen avoidance; Hypoallergenic diet
Pruritus?
PRURITIS
Associated Clinical signs
§ Alopecia § Hot spot
§ Dermatitis § Redness
§ Inflammation § Crusts
§ Hyperpigmentation § Dandruff
Causes
§ Allergy § Infection
§ Ectoparasite § Neoplasia
§ Syringomyelia § Immune-mediated
Diagnosis
§ History: Intensity; Progression; Diet; Environment
§ Physical exam: Lesions; Localisations; Symmetry
§ Skin scraping: Microscopy & culturing
§ Blood exam: Sarcoptes spp. serology; Microfilaria
§ Ex juvantibus diagnosis: Abx; AM; Antiworm; Acaricide
§ Elimination of contact allergens
§ Elimination diet & provocation
§ Allergy tests – Atopy
§ Skin biopsy
Differential diagnosis of pruritis
§ Self mutilation
§ Excessive licking
§ Foreign body (in the paw)
Treatment
Apoquel (Oclacitinib)
Fast treatment for pruritis; anti-inflammatory effect
Complications: Skin nodule
Cytopoint (Lokivetmab)
IL-31; Very responsive; Neutralisation of pruritis
Inject every month
Cyclosporin
Advantage: Very safe; Can ↓ dose once a week
Disadvantage: Possible emetic effect
Contraindication: Neoplasia; Cats with toxoplasma spp. infection
Allergy and hypersensitivity?
ALLERGY & HYPERSENSITIVITY
↑ Reactivity after meeting with a “foreign body”; Results in
inflammation
Allergy: Hypersensitivity of immunological origin
Atopy: Predisposition to develop an allergic reaction
Pseudoallergy: Allergy which is non-specific or non-immunological
Idiosyncrasy: Ø Specific immunological reaction; ↑ Sensitivity of
mastocytes
Allergen: Non-infectious; Non-invasive; Innocuous
IMMUNE-MEDIATED DISORDERS
Immune mediated disorders?
Urticaria?
URTICARIA (HIVES)
Type-I & Type-III hypersensitivity reaction; Acute onset
Causes: Drugs; Vaccines; Insect bites
Clinical signs
§ Localised/generalised wheals
§ Hairs stand up over affected areas
§ Variable pruritis (head)
Treatment: Water soluble Glucocorticoids; Antihistamines
Angioedema?
ANGIOEDEMA
Angioneurotic oedema
Type-I hypersensitivity reaction
Cause: Wasp & bee stings
Clinical signs
§ Extreme swelling of the head, face & feet
§ Laryngeal oedema
Treatment: Adrenaline; Glucocorticoids; Tracheotomy if necessary
Atopic like dermatitis?
ATOPIC-LIKE DERMATITIS (ALD)
Inflammatory & pruritic skin disease with similar CSx to atopic
dermatitis, only there is no evidence of IgE response to allergens.
Flea bite hypersensitivity?
FLEA-BITE HYPERSENSITIVTIY
FAD – Flea allergy dermatitis; Type-I & Type-IV hypersensitivtiy
Predisposed: Dog > Cat; Seasonal
Dog
Usually presents as papular dermatitis on the flank, ventral abdomen,
or caudal body
Chronic cases may produce:
§ Lichenification § Seborrhoea
§ Acral lick granulomas § Alopecia
§ Pyotraumatic dermatitis § Crusting
Secondary infections by bacteria & yeast are common in dogs
Cat
There are four common reaction patterns similar to feline allergic
dermatitis & cutaneous adverse food reactions:
§ Miliary dermatitis
§ Symmetrical alopecia
§ Excoriations
§ Eosinophilic granuloma complex
Pruritis can be constant & intense
Diagnosis
§ Flea dirt
§ History; CSx; Exclusion of other differentials
§ Therapeutic trial → The only way to confirm
Treatment
§ Education of the owner
§ Treat pruritis
§ Prevent secondary infections
§ Topical anti-inflammatories
§ Glucocorticoids: Prednisolone
Contact dermatitis?
CONTACT DERMATITIS
Predisposed: Any age; Some genetic disposition; Dogs with
weakened immune systems
Forms
§ Allergic contact dermatitis: Immune system over-reacts
§ Irritant contact dermatitis Direct damage to the skin
Contact hypersensitivity (allergic contact dermatitis)
Rare; Delayed type-IV hypersensitivity
Cause: Soap; Pollen; Disinfectant; Shampoo; Rubber; Plastic
CSx: Erythema; Macules; Papules; Hyperpigmentation; Pruritis
Diagnosis: Scratch/patch testing
Primary irritant contact dermatitis (normergic dermatitis)
Must be differentiated from contact hypersensitivity (more
common)
Cause: Acids; Alkalis; Detergents; Soaps; Solvents
CSx: Localisation where hair is sparse → Pruritis; Red rash
Treatment: Bathing; Topical glucocorticoid ointment
Feline Psychogenic alopecia?
FELINE PSYCHOGENIC ALOPECIA
“Caused by anxiety neurosis”; Excessive licking & grooming
Thought that grooming results in endorphin release → ↑ Stress →
Over-grooming
Clinical signs
§ Excessive licking & grooming
§ ↑ Anxiety; Nervousness
§ Alopecia with no underlying inflammation
§ Hairs at the affected site are broken
Treatment
§ Environmental enrichment
§ Pheromone products
§ Clomipramine (antidepressant)
§ Fluoxetine (antidepressant)
Feline Miliary Dematitis?
FELINE MILIARY DERMATITIS
Causes: Flea-bite hypersensitivity; FAD; Atopy; Drug
hypersensitivity; Parasites; Essential FA deficiency
Clinical signs
§ Mild popular reaction
§ Pruritis
§ Self-trauma from licking
§ ↑ Hairball vomiting
Feline Eosinophilic Granuloma Complex (ECG)?
FELINE EOSINOPHILIC GRANULOMA COMPLEX (ECG)
Forms
§ Indolent ulcer (upper lip): Raised border; Swelling
§ Eosinophilic plaque (abdomen; medial thigh)
Demarcated; Flat swellings of skin; Reddened appearance;
Alopecia; Pruritis
§ Eosinophilic granuloma (mouth/tongue/palate/anywhere):
Nodular/linear area of raised, thickened skin; Hair-loss;
Ulceration; Pruritis
Cause: Hypersensitivity reaction
Treatment
§ Systemic glucocorticoids (Prednisolone)
§ Megestrol acetate
