How do you perform a hair pluck?
Pluck hair with hemostat Place in mineral oil on microscope slide Cover with cover slip Examine with dry objectives
How do you perform a skin biopsy?
Do not wash or prepare site!!! OK to gently clip hairs Use SQ lidocaine for anesthesia (fractious animals use sedation) Place biopsy in 10% neutral buffered formalin Specimen size to solution volume should be at least 1:10 Nasal planum, footpads, oral ulcers need general anesthesia
How do you perform a sub-gross examination?
magnification + lighting, e.g. otoscope with no cone
How do you perform a Wood's Lamp examination?
Wood’s lamp should be turned on for 5- 10 minutes before use Fluorescence is apple-green in color, and follows hair shafts
How do you perform an acetate tape preparation?
Press on lesion Place on slide sticky side down, (dry for cytology, mineral oil for parasites) Look for parasites (4x & 10x) OR Stain for bacteria & yeast (100x)
How do you perform an aspirate for cytology?
Collected with needle +/- syringe Material placed on dry slideHeat fix Rapid stain (Diff-Qwik ®) Scan for areas of interest with 4x objective, then use 100x with immersion oil
How do you perform an ￼exudate / pustule smears for cytology?
Collect material w/ cotton swab Roll material on dry microscope slide Heat fix Rapid stain (Diff-Qwik ®) Scan for areas of interest with 4x objective, then use 100x with immersion oil
How is diascopy performed, and what does it tell you?
Pressure applied on the skin through clear plastic or glass to determine if erythema is due to vascular dilatation or bleeding into the skin
How would you perform a skin scrape for parasites?
Clip heavily haired areas Place small amount of oil on spatula Scrape blade across skin perpendicular to the surface Place material in mineral oil on slide Cover with cover slip Examine with 4x or 10x objective
How would you perform a skin scraping for cytology?
Spatula or #10 blade Clip heavily haired areas Scrape dry blade across skin perpendicular to the surface Always￼￼ superficial Smear material on dry slide Heat fix Rapid stain (Diff-Qwik ®) Scan for areas of interest with 4x objective, then use 100x with immersion oil
If more than one animal is affected with a skin condition, what does this tell you?
It's either contagious, nutritional or toxic etiology
What are the three main causes of folliculitis?
pyoderma, demodex, dermatophytosis
What are the types and benefits of skin biopsy?
wedge (better for deep, fragile lesions; takes more tissue, more time, GA usually) punch (easier, speedier, fewer sutures; can get smaller sample, more traumatic, hard to orient)
What can cause false positive Wood's Lamp examinations?
topical medications, dander
What is a bulla?
A large vesicle Bulla can form in the epidermis, between the epidermis and dermis, (dermal-epidermal junction), or within the dermis
What is a collarette?
Narrow rim of loosened stratum corneum that overhangs peripheral edge of acircumscribed skin lesion Evolve from pustules Post inflammatory hyperpigmentation or non pigmented halo along w/ footprints of previous pigmentation
What is a crust?
Accumulated fragments of cornified epidermal cells (scale) plus dried residue of serum, blood, or pus Crusts imply inflammation
What is a macule?
A circumscribed change in skin color without elevation or depression of the surface. Epidermis only
What is a nodule (two kinds)?
Large papule or solid, deep-seated mass in either dermal or subcutaneous tissue Dermal nodule: skin and nodule move over underlying tissue Subcutaneous nodule: skin moves over nodule and underling tissue
What is a papule?
A circumscribed solid elevation of the skin, implies involvement of both the epidermis and dermis The most common skin lesion
What is a patch?
A large macule
What is a plaque?
A large, usually flat-topped circumscribed elevation of the skin Plaques often evolve from confluent papules
What is a pustule?
A circumscribed elevation of the epidermis containing purulent material (pus) A vesicle containing pus
What is a scale?
￼Accumulated fragments of dead, cornified epidermal cells (stratum corneum) Scale results from altered keratinization or cornification
What is a tumor?
Large nodule or neoplastic mass
What is a vesicle?
A circumscribed elevation of the epidermis containing serous fluid Vesicles are fragile & readily rupture￼￼￼￼￼
What is a wheal?
A well-circumscribed flat-topped firm elevation of the skin with a well-demarcated, palpable margin Produced by dermal edema - wheals should pit
What is an erosion?
Superficial denudation of the skin confined to the epidermis Erosions do not damage or breach the dermal-epidermal junction (BMZ) Erosions ooze serum, but do not bleed￼￼￼￼￼￼
What is an ulcer?
A defect of the skin extending through the dermal-epidermal junction (BMZ ) into the dermis or even deeper Ulcers bleed Includes pemphigus foliaceus
What is excoriation?
A lesion produced by self-trauma (underlying pruritus) Excoriations can be either erosions or ulcers
What is lichenification?
A thickening of the skin (usually with hyperpigmentation) with increased prominence of the normal surface epidermal architecture Indicates chronicity of skin disease ± self-trauma
What is pruritis?
sensation that elicits a desire to scratch
What is the best diagnostic test for dermatophytosis?
What materials are necessary for parasite skin scraping?
Spatula or #10 blade Mineral oil on microscope slide Glass cover slip
What parasites can be discovered with a skin scraping?
surface: scabies (notoedres), cheyletiella, chorioptes follicular: demodex
When is a bacterial culture indicated?
No response to staph abx Maybe if have been on abx in last 6-12 months
When is a hair pluck useful, and what would you see?
pruritis (see broken hair ends), demodicosis / liec / cheyletiella (eggs or parasites on hair), color dilution (melanin clumping on outisde of shaft), dermatophytes, follicular casting
When would you use a Wood's Lamp?
~60% of Microsporum canis fluoresce = diagnosis of dermatophytosis
When would you use an aspirate for cytology?
neoplasia, bacterial and systemic fungal infections
When would you use exudate / pustule smears for cytology?
bacterial, systemic fungal, otitis externa, anal saculitis, pemphigus foliaceus
When would you use skin scrapings for cytology?
Yeast (malassezia), bacterial (staph, secondary)
Why do some dermatophyoses fluoresce with a Wood's Lamp?
tryptophan metabolite that is produced only ON the animal
How does skin act as a sensory organ?
Dermatomes supplied with large sensory nerves that terminate in free nerve endings & more specialized receptors
What sensations do free nerve endings conduct?
Touch, temperature, pain, pruritus
What are cutaneous receptors for?
Specialized corpuscular receptors - Pacinian and Meissner’s corpuscles Ruffini’s end organs, Merkel’s discs These are mechanoreceptors (pressure, vibration) – do they transmit pruritus?
How is pruritus perceived?
Sensation of itch carried centrally from free nerve endings by: - Non-myelinated, slow conducting C fibers most important (pruritus, pain, heat) - Myelinated, rapid conducting A delta fibers (noxious stimuli, cold)
How does pruritus reach the brain?
lateral spinothalamic tract
What are the three pain / pruritus theories?
Specificity theory: different subsets of nociceptors transmit pain or pruritus Pattern theory: spatio-temporal pattern of neural activity permits distinction Central processing theory: central processing differences permit distinction between the two sensations
What are the major pharmacological mediators of pruritus?
Histamine, PgE1, leukotrienes (LTB4), opioid peptides, substance P
What is the threshold phenomenon?
What happens IN the animal A certain pruritic load may be tolerated by an individual without provoking clinical signs, but an increase in that load may push that individual over the threshold initiating clinical signs of pruritus
What does Summation of Effect mean?
What happens TO the animal Additive pruritic stimuli from different chemical mediators or coexistent skin diseases may raise an animal above its individual pruritic threshold
What are the parts of the hair cycle, and what do they do?
Anagen stage - Mitotically active hair growth phase Catagen stage - Involutional, no growth Telogen stage - Long transitional ‘resting’ phase, no active metabolism Exogen stage - brief phase, telogen hair is shed 'pushed out' by new anagen hair
What major events can affect the hair cycle?
Endocrine disease - Hormonal status Vascular sustenance - Ischemia of hair follicle Inflammation - Near hair bulb Metabolic abnormalities Dysplasia - Genetically pre-programmed
How can alopecia be classified?
Traumatic - Common, secondary to pruritus Non-traumatic - Less common Congenital - Rare, inherited, permanent Acquired - Common, many causes Cicatricial - Follicular destruction & scarring (much more common in humans) Non-cicatricial - Hair regrowth possible if causative factors can be identified & corrected
What does non-immunological, related to pharmacological action drug reaction look like?
Predictable, dose dependent Anti-metabolites, other immunomodulators Alopecia, purpura, poor wound healing, infection
What does a immunological drug reaction look like?
Not predictable, relatively dose independent Abnormal production of IgE, IgA, IgG, IgM Immediate, cytotoxic, immune complex or delayed hypersensitivity
What are the clinical features of adverse drug reactions?
can mimic any skin disease
Where are some common places on the body to be affected by an adverse drug reaction?
medial pinna, ventrum, oral cavity, generalized
What is the most common hx of an adverse drug reaction?
Was on a drug previously, stopped, was put back on it in last 2 weeks, developed cutaneous symptoms
What clinical syndromes / diseases are commonly seen with adverse drug reactions?
Toxic epidermal necrolysis Erythema multiforme (minor & major) Vasculitis Pemphigus foliaceus Urticaria Maculopapular eruptions Injection site drug reactions Erythroderma Exfoliative dermatitis Purpura Fixed drug eruptions Vesiculobullous reactions Lichenoid drug eruptions Sterile pustular erythroderma (Superficial suppurative necrolytic dermatitis)
What can trigger the clinical syndromes of erythema multiforme and toxic epidermal necrolysis?
Neoplasia, infection, idiopathic, cutaneous adverse drug reaction
What is erythema multiforme?
Erythematous macules and papules, target lesions, erosions, ulcers, collarettes Sites - Truncal (esp. ventrum), mucocutaneous junctions, face, ears
What is toxic epidermal necrolysis?
Macular erythema -> confluent erythema, ulceration, pain. The whole skin will slough -> sepsis -> DIC -> death Sites - Face, trunk, mucocutaneous junctions, pawpads
What are some common drugs that trigger adverse reactions in dogs, cats and horses?
abx: TMS, penicillins NSAIDs: ace, bute (horses only)
When do you most commonly see topical adverse drug reactions?
When treating otitis externa, applying topical flea control Will see lesions at site of application, except Promeris
How are adverse drug reactions managed?
Withdraw suspected drug (if not known, withdraw all drugs) Avoid the suspect drug & all related drugs in the future Supportive care Depending on the cutaneous reaction immunosuppressive therapy may be indicated
What is the px for adverse drug reactions?
Most self-limiting after drug withdrawal (within 2-14 days) E.M. - Potentially life-threatening T.E.N. - Always life-threatening
What do dermatophytes live on?
keratin (dead), therefore skin, hair and claws can penetrate deeper in immune compromised animals or when trauma present
What are the three dermatophyte genera?
Microsporidium, Trichophyton, Epidermophyton
What is the natural host for M. canis?
What is the natural host for T. mentagrophytes?
What is the natural host for M. gypseum?
What dermatophytes to horses get?
T. equinum T. mentagrophytes T. verrucosum M. equinum
What is the natural host of epidermophytes?
humans, so reverse zoonosis
What are some of the risk factors for developing dermatophytosis?
young age, poor nutrition, stress, debilitating disease, immune compromised
What are the clinical signs of dermatophytosis?
alopecia, scaling, crust, papule, erythema, pruritus, weak keratin
What is the most common dermatophyte to infect cats?
Where are cats affected with dermatophytosis?
face, ears, legs asymmetrical!
Where are dogs affected with dermatophytosis?
face, tail, feet
What is a kerion?
Tumor-like form of dermatophytosis, is exudative and can look for fungal hyphae on smear
What does dermatophytosis on a dog muzzle tell you?
likely T. mentagrophytes from chasing burrowing rodents
What are the clinical symptoms of dermatophytosis in dogs?
alopecia, crusts, papules, pustules
What are the clinical symptoms of dermatophytosis in horses?
initially urticarial alopecia and crusts in area of tack can affect only the coronary band
How can dermatophytosis be dx?
hair pluck (KOH or chlorphenolac clearing agents), Wood's Lamp fluorescence, biopsy with special stains, culture (definitive)
What is the culture media for dermatophytes?
DTM (should turn red within 48 hours of growth) +/- Sabouraud's (allows for colony ID)
What does a positive DTM culture look like?
colony is white of pale tan, fluffy, turns agar red in first 48 hours of growth, growth occurs within 3 weeks of inoculation
How can M. canis and T. mentagrophytes be differentiated on a stained cytology?
terminal knob on M. canis
How is dermatophytosis tx?
self cure in 3 months (contagious and shedding during) systemic, topical + environmental txt needed systemic: imidazole, terbinafine, griseofulvin topical: imidazole (esp enilconazole), chlorhexidine, lime-sulfur environment: 100% bleach or throw away tx until 3 negative cultures 1-2 weeks apart
What imidazoles should be used for canine dermatophytosis?
What imidazoles should be used for feline dermatophytosis (or small dogs)?
What are the AE of imidazoles for dermatophytosis?
GI upset, hepatopathy, drug interactions Renal clearance in fluconazole
What are your considerations for giving griseofulvin?
give with high fat meal for absorption animals > 12 weeks old and not pregnant AE: V. leukopenia (esp FIV+), teratogen
How does Lufenuron work, and what are your considerations?
inhibits chitin production give with meal likely ineffective, but very safe
What are the systemic txt for horses with dermatophytosis?
NaI, griseofulvin (not if pregnant) fluconazole
What are your considerations for using topical lime sulfur?
Smells terrible, stains sterling silver, stains white hair to yellow, very effective, safe for any age
What do dermatophyte vaccines achieve?
smaller lesions T. verrucosum successful in cattle
What conditions are topical therapies used for?
seborrhea, allergy, infection
What are the types of vehicles for topical therapy?
shampoo, pledgets, soaks, dips, powders, lotions, creams, ointments, gels, sprays
What is keratoplastic?
normalizes epidermal cell turnover
What is keratolytic?
decreases keratinocyte adhesion
What are the possible activities for topical therapy agents?
antibacterial antisebhorreic antifungal antipruritic antiparasitic moisturizing sunscreen deterrent
What are the most common antibacterial agents effective against?
Staph pseudintermedius (otitis externa and superficial pyoderma), rarely P. aeruginosa
What is the activity of benzoyl peroxide?
antibacterial keratolytic degreasing *works well with sulfur* warning: bleaches fabrics and hair, very drying
What is the activity of ethyl lactate?
antibacterial (lowers skin pH) "elegant shampoo"
What is the activity of chlorhexidine?
antibacterial antifungal (>3%) animal can be dirty (ok to have organic debris)
What is the activity of sulfur / salicylic acid?
antibacterial antifungal (yeast) antisebhorreic (keratoplastic and keratolytic) antipruritic
What is the activity of mupirocin?
antibacterial topical only, nephrotoxic on MM
What is the activity of Triclosan?
antibacterial use with sulfur / salicylic acid
What is the activity of silver sulfadiazene?
antibacterial antifungal promotes re-epithelialization, good for burns
What is the activity of povidone iodine?
antibacterial, but very irritating
What is the activity of propylene glycol?
antibacterial antifungal humectant
What are some topical antifungal agents?
Ketoconazole, Miconazole, Clotrimazole, Enilconazole, Chlorhexidine, Thiabendazole, Nystatin, Lime sulfur
What is the activity of lime sulfur?
antifungal antiparasitic (sarcoptes, cheyletiella, notoedres, lice, chiggers)
What is seborrhea?
Disturbance of epidermal cell turnover time that results in excessive scaling and crusting Can be oily, greasy or dry forms
What is the activity of tar?
antiseborrheic local anesthetic *toxic in cats* smells bad
What is the activity of Amitraz?
Spot-on flea txt monoamine oxidase inhibitor antiparasitic (demodex, sarcoptes, cheyletiella, otodectes, notoedres) *can be toxic*
What are some antipruritic or anti-inflammatory agents?
colloidal oatmeal, corticosteroids, topical lidocaine or pramoxine, antihistamines, tar (not in cats!), sulfur
What is the activity of corticosteroids?
anti-inflammatory immunosuppressive antimitotic
How are corticosteroids immunosuppressive?
inhibits CMI decreases cytokines decreases lymphocytes
When are the AE of corticosteroids?
pu, pd polyphagia protein catabolism fat redeposition GI ulcers immunesuppression silent uti or pyoderma adrenal gland atrophy mood changes hepatopathy develop DM laminitis in horses derm: skin atrophy, comedones, hyperpigmentation, alopecia (increased telogen follicles), bruising, poor wound healing, infections, calcinosis cutis
Why do corticosteroids cause pu, pd?
increased GFR + inhibits ADH -> loss of Na and water = pu pu -> pd
Why do corticosteroids cause GI ulceration?
PgE2 is protective of gastric mucosa *never use with NSAIDs for this reason*
What is calcinosis cutis?
dystrophic calcification of skin = ossification of dermal collagen see on ventrum and dorsal neck
Which corticosteroids are short acting?
Which corticosteroids are intermediate acting?
prednisone, prednisolone, methylprednisolone
Which corticosteroids are long acting?
triamcinolone, dexamethasone, bethamethasone
Do cats ned higher or lower doses of corticosteroids than dogs for immunosuppressive effects?
2x dog dose