Equine Derm ECVD Video Flashcards
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
Risk factors of laminitis (4)
1) Equine metabolic syndrome
-Increased baseline insulin levels
2) PPID –> insulin resistance
3) Ponnies
4) Older age
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
How potent is prednisolone compared to hydrocortisone
4x more potent than HC
Does prednisolone have an increased risk of inducing laminitis
No
How potent is dexamethasone compared to hydrocortisone
25x more potent than HC
Does dexamethasone have an increased risk of inducing laminitis
Possibly a small increase
How potent is triamcinolone compared to hydrocortisone
5x more potent than HC
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
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
What is 11-beta HSD-2
Enzyme to inactivate steroids
Triamcinolone and dexamethasone are more resistant to inactivation by this enzyme
What does active corticosteroid do to the distal limb?
Vasoconstriction to hoof, fibroblasts, keratinocytes
How long does prednisolone cause insulin resistance?
1 day
How long does triamcinolone cause insulin resistance?
7 days
How long does dexamethasone cause insulin resistance?
3 days
Is there an increased risk of laminitis with corticosteroids in HEALTHY horses (without risk factors)?
No
Which breeds are more prone to pastern dermatitis
Cold blooded, heavy horses (draft horses)
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)
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
Where on the body should you assess a horse with MEEDS (eosinophilic dermatitis)
Coronary band + mouth (stomatitis)
Thoroughbreds and standardbreds ONLY affected
Differentials for nodules on pastern (3)
1) Chronic progressive lymphedema, verrucous dermatitis
2) Sterile, infectious pyogranulomas (Habronema parasitic!)
3) Neoplasia
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
What clinical lesions would you expect to see with a contact reaction?
Crusting, erosions, ulcerations
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
