Intro to derm Flashcards
What mechanism drives the coast shedding?
- dependent upon daylight hours
- Melatonin and prolactin driven
- Short days»Increase melatonin and declining prolactin»>winter coat growth
How long is the full hair cycle?
4-6 weeks
What are the 4 types of hypersensitivities? Give an example associated to skin for each
Type 1 hypersensitivity: IgE mediated involving the release of histamine by mast cell. Biphasic in nature. Aggravated after serial exposure. Insect-bite hypersensitivity AKA Sweet itch
Type 2 hypersensitivity: IgG mediated cytotoxic response associated with complement binding. Pemphigus complex
Type 3 hypersensitivity: Immunocomplex deposition on endothelial beds, neutrophil activation»vasculitis. Pastern leukocytoclastic vasculitis, purpura haemorrhagica, Lupus..
Type 4 hypersensitivity: T- cell mediated. Insect-bite, drug eruptions
What history is important when investigating a derm case?
Horse signalment
* Age, sex
* Duration of the ownership
* Origin of the horse (country, county, rescue)
* Travelled abroad
Diet (hay, haylage, grain, commercial feeds, supplements)
Type of bedding (straw, shavings, cardboard, rubber matts)
Lifestyle: out on pasture, stabled, type of barn…
Tack and general cleaning practices: saddle, reins, girth, boots
Routine care and last administration: endoparasites, vaccinations, ectoparasites control
Any previous medical condition
Any current drug therapy: oral, topical or IV
Other horses or people showing skin lesions
**Details of skin condition **
* Location and duration
* Localized or generalized
* Presence of pruritus
* Seasonality
* Treatment attempts
What lesion distributions are associated with insect bite hypersensitivities, pinworm, lice infestation, fungal infections, rain scald, mud fever, urticria and contact dermatitis?
- Mane, tail and ventral line: Insect-bite hypersensitivity
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Base of the tail : hair loss, tail rubbing
- Oxyuris equi AKA pinworm
- Insect-bite hypersensitivity
- Lice infestation (normally more truncal)
- Group, chest, neck sometimes face: fungal infections
- Back, chest, rump, sometimes face: “rain scald “
-
Distal limbs:
- “Mud fever” : bacterial ± fungal
- Mite infestation: Trombiculiasis, chorioptic mange
- Truncal, neck occasional head: urticarias, atopia, lice infestation
- Back, girth area: contact dermatitis, fungal infections
What are examples of primary lesions? What conditions are commonly associated?
- macule and patch: alopecia areata, vitiligo
- papule and plaque: bacterial infections, fungal infections and sometimes parasites
- vesicle: EHV-3, vesicular stomatitis and pemphigus foliaceus
- pustule: bacterial infections, insect bite and fungal infections
- wheal: urticaria, food allergies and insect sting
- nodule: papilloma, sarcoid, melanoma, eosinophilic granuloma, exuberant granulation tissue
- tumour: melanoma, sarcoid, cutaneous lymphoma, fibroma, mastocytomas and histiocytoma
- abscess: streptococcal, clostridial (pseudotuberculosis) and traumatic
What are examples of secondary lesions?
- alopecia
- scales
- crust
- erosion
- ulcer
- lichenification
- hypo/hyper pigmentation
What are typical clinical patterns in derm?
- Pruritus
- Crusting and scaling
- Ulceration and erosions
- Nodules
- Pedal or pastern dermatitis
- Urticaria
- Pigmentary abnormalities
When would you use coat brushings? How do you assess what you’ve sampled?
- Ideal for ectoparasites
- Magnification lens or microscope
Identify these ectoparasites
sucking louse, biting louse, feather mite
What are typical findings when using hair plucks as a diagnostic technique? What do they mean?
- Fracture shafts: self-inflicted trauma: pruritus
- Swollen frayed shafts with fungal spores: dermatophytosis
- Exclamation mark-shaped hair bulbs: Alopecia areata
What are skin scrapes used for? How would you analyse your samples?
- Ideal for mites and dermatophytes (fungi)
- Mites: add 2 drops of mineral oil on the microscope slide
- Dermatophytes: blue staining on microscope slide and qPCR collected in sterile containers
What do you need to remeber when biopsying a suspected sarcoid?
Take the whole thing out
What allergy tests exist? When should they be used?
Serum (SAT): unreliable.
- Still can provide some information but require careful interpretation along with clinical exposure: test only in acute disease (flare)
Intradermal (IDT): better diagnostic yield but poor repeatability
- Most reactions to mites, dusts, insects, plants…
- Useful to establish immunotherapy treatments
