Equine Derm ECVD Video Flashcards by Treasa Clifford

What is the mechanism by which corticosteroids can induce laminitis?

Corticosteroids increase insulin level, induce insulin resistance. Long term elevated insulin and can lead laminitis

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Risk factors of laminitis (4)

1) Equine metabolic syndrome
-Increased baseline insulin levels
2) PPID –> insulin resistance
3) Ponnies
4) Older age

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Why would you use an oral glucose tolerance test as a dermatologist

Need to r/o EMS before corticosteroids if a horse is obese –> use an oral glucose tolerance test to check insulin, glucose, triglycerides

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How potent is prednisolone compared to hydrocortisone

4x more potent than HC

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Does prednisolone have an increased risk of inducing laminitis

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How potent is dexamethasone compared to hydrocortisone

25x more potent than HC

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Does dexamethasone have an increased risk of inducing laminitis

Possibly a small increase

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How potent is triamcinolone compared to hydrocortisone

5x more potent than HC

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How diabetogenic is triamcinolone compared to dexamethasone

SAME diabetogenicity, even though LOWER potency

Triamcinolone has a shorter serum half life, BUT binds onto CCR for LONGER –> longer lasting insulin resistance

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What allows dexamethasone and triamcinolone to stay in the body for a longer period of time?

Dexamethasone and triamcinolone are resistant to inactivation by 11-beta HSD-2

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What is 11-beta HSD-2

Enzyme to inactivate steroids

Triamcinolone and dexamethasone are more resistant to inactivation by this enzyme

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What does active corticosteroid do to the distal limb?

Vasoconstriction to hoof, fibroblasts, keratinocytes

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How long does prednisolone cause insulin resistance?

1 day

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How long does triamcinolone cause insulin resistance?

7 days

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How long does dexamethasone cause insulin resistance?

3 days

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Is there an increased risk of laminitis with corticosteroids in HEALTHY horses (without risk factors)?

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Which breeds are more prone to pastern dermatitis

Cold blooded, heavy horses (draft horses)

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Risk factors for pastern dermatitis (6)

1) Older age
2) Breed (draft)
3) Heavy feathering
4) Unpigmented skin (pigmentation = protective against photosensitization, photo-aggravated vasculitis)
5) Damage to skin barrier
6) UV light (esp unpigmented skin)

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Differentials for pastern dermatitis (15)

1) Bacterial (Staph, Strep, E coli, Pseudomonas, others)
2) Chorioptic mange
3) Contact hypersensitivity
4) Dermatophyte
5) Helminths
6) Hepatocutaneous syndrome
7) Localized sarcoidosis
8) MEEEDS (eosinophilic dermatitis and stomatitis- CORONARY BAND)
9) Photodermatitis
10) Pemphigus foliaceus
11) Pemphigus vulgaris
12) Sarcoids
13) Selensiosis
14) Trombiculosis (Chiggers)
15) Yeast infection

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Where on the body should you assess a horse with MEEDS (eosinophilic dermatitis)

Coronary band + mouth (stomatitis)

Thoroughbreds and standardbreds ONLY affected

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Differentials for nodules on pastern (3)

1) Chronic progressive lymphedema, verrucous dermatitis
2) Sterile, infectious pyogranulomas (Habronema parasitic!)
3) Neoplasia

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What’s your diagnosis: Hair above coronet sticking straight out, thin bead of abnormal horn and tightly backed growth rings below coronet.

Coronary Band Dystrophy

Compact parakeratotic hyperkeratosis. Hydropic degeneration

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What clinical lesions would you expect to see with a contact reaction?

Crusting, erosions, ulcerations

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Why are haptens not immunogenic on their own?

Their sequence is too simple to bind to MHC cl II, so not presented to T cells BUT when they bind to another peptide, the COMBINATION can be immunogenic

What topical product is a hapten that induces contact hypersensitivity

Chlorhexidine

What is your top differential diagnosis when a horse has pastern dermatitis with crusting and pruritus in the fall/winter

Chorioptic mange

What is your top differential diagnosis when a horse has pastern dermatitis with crusting and pruritus in the summer/early fall

Trombiculosis (chiggers) **This is in Europe *Chiggers usually live in decaying plant matter, but need to feed on blood for larval life stage

3 chemicals that cause percutaneous photosensitization

1) Plants 2) PABA (used in sunscreen? UVB filter) 3) Hexachlorophene (disinfectant)

Distribution of pastern vasculitis

Hind limbs > front limbs Lateral/medial > cranial/caudal

In 1 study, which sex was more predisposed to vasculitis

Mares (but not repeatable in a different study)

Which clinical sign was present in most horses with vasculitis?

SQ edema

Which infection can cause vasculitis in horses?

Purpura hemorrhagica 2' -Streptococcus equi (strangles) -Corynebacterium pseudotuberculosis

What is the prognosis for vasculitis in horses

Guarded. 63% survival rate

What is a negative prognostic indicator in horses with vasculitis?

Fever

Which bacteria is associated with vasculitis

Staphylococcus intermedius

While photoaggrevated vasculitis causes crusts/erosions/ulcers, what clinical signs are seen with pigmented vasculitis?

Scale, alopecia

Thickened nodules, corrugated skin of distal limb in a draft horse. Diagnosis?

Chronic progressive lymphedema

Labwork values indicative of hepatocellular injury

AST, SDH, GLDH

Labwork values indicative of biliary disease

GGT, ALP, Bile acids

Labwork values indicative of inflammation

Fibrinogen, SAA, TP, Albumin

Risk factors for chronic progressive lymphedema (7)

1) Older age 2) Larger cannon circumference 3) Poor hoof grooming 4) Fetlock feathers 5) Larger ergots, chestnuts 6) Pastern bulges 7) Poor hygienic conditions

Type of inflammatory cell seen in chronic progressive lymphedema

T cell perivascular inflammation with lymph edema and dermal fibrosis

What is the primary tissue affected with progressive lymphedema

Altered ELASTIN metabolism --> impaired lymphatic drainage in distal extremities. Inflammatory changes are 2' to lymph issues

Differentials for alopecia and scaling of distal limbs (4)

1) Dermatophyte 2) Bacteria 3) Vasculitis of pigmented skin 4) Localized sarcoidosis (localized lympho-histiocytic granulomatous dermatitis); unknown trigger for this inflammatory reaction

Is localized sarcoidosis the same as generalized sarcoidosis?

NO. Unknown trigger for localized; not associated with BPV. Better prognosis than generalized sarcoidosis (which is also not BPV associated)

Coronary band differentials (7)

1) Infections DRY/FISSURES 2) Coronary band dystrophy 3) Selenosis EROSIVE/ULCERATIVE/CRUSTED 4) Pemphigus 5) Multisystemic Equine Eosinophilic Epitheliotrophic Dermatitis and Stomatitis (MEEEDS) 6) Sarcoidosis (Multisystemic granulomatous disease) 7) Hepatocutaneous syndrome

Seleniosis signs

Dry, fissures of coronary bands

MEEDS prognosis

Grave

T or F: Horses can have hepatocutaneous syndrome

True

Differentials for spontaneous, nonpruritic noninflammatory, alopecia (5)

Multifocal: 1) Alopecia areata 2) Demodicosis Generalized: 3) Alopecia areata (rare to be generalized) 4) Telogen/anagen effluvium 5) Selenium toxicosis

Differentials for sontaneous, nonpruritic alopecia WITH crusting (4)

1) Bacterial folliculitis 2) Occult sarcoid 3) Dermatophilosis 4) Dermatophytosis

If you are suspicious of Staphylococcal folliculitis, what other differentials should you think of (look similar)?

Dermatophilosis Dermatophytosis

Linear keratosis (crusting, alopecia). Most common body sites

Rump, shoulder, neck, lateral chest

Age with linear keratosis

Young, persists lifelong

Does linear keratosis track nerves, vessels, dermatomes?

No!

Would you expect orthokeratosis or parakeratosis with linear keratosis?

Orthokeratotic (as opposed to Coronary Band Dystrophy, which is parakeratotic)

What is the most common cause of generalized crusting?

Pemphigus foliaceus

Generalized granulomatous disease (sarcoidosis) prognosis

Grave Eventually get "wasting syndrome" with internal organ involvement --> die

Diagnosis?

MEEDS

Differentials for generalized crusting/scaling in the horse? (6)

1) Pemphigus foliaceus 2) Generalized granulomatous disease (sarcoidosis) 3) MEEEDS 4) Lupus 5) Cutaneous lymphoma 6) Toxicosis (selenium, arsenic, mercury, iodine)

Most common cutaneous neoplasms in the horse

*Sarcoids *Melanoma *SCC *MCT

Incubation time for equine viral papilloma on the muzzle

60-70d

VIrus that causes equine papilloma virus on muzzle

EcPV1

Vector for EPV on muzzle

Insects

Age for equine viral papillomas (muzzle)

Young (<2 yr old) Spontaneously regresses in 3-4 months usually (1-9 months)

Body regions affected by equine viral papilloma

**Muzzle**, eyelid, genitalia, legs

Equine ear papillomas, aural plaque: viruses

EcPV 1,3,4,5,6 Coinfection in 59%

Vector for Equine ear papillomas, aural plaque

Black fly

Age for Equine ear papillomas, aural plaque

> 1 yr old Require treatment

Black flies can spread EcPV. Which form is usually spread by this fly?

Equine ear papillomas, aural plaque

What other sites of the body should you check in a horse with Equine ear papillomas?

Concave pinnae Genitalia Mammaries

Most common location of SCC

Eyelids, external genitalia

Type of skin affected by SCC

Unpigmented

Risk factors for SCC

UV light EcPV2 (the ONLY papilloma not indicated in aural plaques)

Differential for nodules near frictional areas (2), ie saddle frictional areas

-Eosinophilic granulomas!!! -Infectious granulomas

Most common tumor on ventral tail/perianal area in grey horses

Dermal melanoma (also, lips, eyelid, sheath, muzzle)

Gene associated with grey horse phenotype, dermal melanoma progression

STX17 (and agouti-signaling protein, ASIP) (Risk of metastasis, look at soft palate, gutteral pouch)

What can equine papilloma transform into?

SCC EcPV2

Where on the body are sarcoids found?

Anywhere! More common where skin is thin (ie frictional areas, face)

Most common skin tumor in horses

Sarcoid

Viruses associated with sarcoids

BPV 1 & 2

What type (greek letter) papillomavirus is BPV 1?

DELTA papilloma virus This means not only does it infect keratinocytes, but ALSO dermal fibroblasts

Oncogenes associated with sarcoids from BPV 1, 2

E5, E6, E7 Maintenance of infection + neoplastic transformation of fibroblasts Degrade p53 , so can't regulate cell cycle Affect chromosome stability

What genetic mutation is a potential predisposition for development of Sarcoids?

MHC class II

Breed that get sarcoids LESS frequently

Standard bred horses

Most common nodular skin disease in horses

Collagenolytic granulomas (eosinophilic granuloma w/collagen degeneration) --> Calcify 2' insect bites > trauma, atopy Often seasonal

Treatment of choice for Sporotrichosis schneckii in horses

Ethylene diamine dihydroiodide (EDDI)

Breed of horse predisposed to panniculitis

Shetland ponies Steatitis of weaning foals

Genetic predisposition for equine sarcoids

Certain Equine Leukocyte Antigen (ELA) alleles increase risk: A3, W13