Equine dermatology 1 Flashcards

Question

Discuss the disease profile of urticaria?

Answer 1

**= clinical sign NOT the disease** * Very Common * Often acute presentation * Cause in most cases is not determined- idiopathic * Transient or persistent **Causes include** * Insect bite (flies) / sting * Atopic dermatitis * Contact allergy RARE (wood shavings, medications/home remedies) * Food allergy cereals)- RARE * Drug reactions eg. Alpha-2 sedatives, penicillin (often carrier not drug), EPZ(bute) - RARE * Dermatographism- pressure induced * Exercise- induced * Cold induced * Dermatophytosis * Idiopathic * Autoimmune disease

Answer 2

**Clinical signs** * Multiple, raised oedematous papules, wheals, plaques * Variable size * Variable distribution- commonly head, neck, trunk * Lesions pit on pressure * Doughnut shape = gyrate form but appearance doesn’t correlate with underling cause! * Can be diffuse and ooze serum = angioedma * Variable pruritus

Answer 3

**Full history** **Clinical signs** * Contact- drip patterns if liquid, progressive lesions where O keeps applying a topical tx and lesions get worse! * Eliminate other problems- skin scrape * Skin biopsy in persistent cases- often unrewarding but useful for ruling out other problems * Dermatographism= write on skin with blunt object,wheal develops within a few minutes

Answer 4

* Dermatophytosis ( culture/biopsy to eliminate) * Insect bites * Erythema multiforme ( clip off hair, central haemorrhagic focus in wheals) RARE * Contact hypersensitivity (rare, doesn’t cause wheals ) * Infectious/immune mediated vasculitis- Purpura haemorrhagica, cutaneous necrosis, diffuse angiodema

Answer 5

* Acute onset /transient / may resolve spontaneously24-48h * SO no tx may be necessary for first episode * Remove contactant- warm water wash * Avoidance of allergen ! * Fly avoidance- barriers/repellents * Most cases --\> steroid responsive- IV dexamethasone 0.05-0.1 mg/Kg * Anaphylactic shock- combination adrenaline, NSAID and Steroid may be needed * Low dose steroids eg. Prednisolone 0.5-1.0 mg/kg PO SID then decreasing doses 1-2 weeks * ? Antihistamines – none licensed, may cause sedation * ?Omega 3 fatty oils- anti-inflammatory effect eg. Linseed oil * ?pentoxyphylline- if concerns wrt steroid use (used in dogs) 10mg/kg BID PO has anti-inflammatory effect ( side effect- hyper excitability)

Answer 6

* The **MOST COMMON** skin lesion in the horse (35-90% of all skin neoplasms) * Fibroblastic tumour which may be locally aggressive, and typically non-regressive * Certain equine leucocyte antigens (ELAs) associated with increased susceptibility * Predilection sites include: (FLIES?) * Ventrum, inguinal region, axilla, periocular region * May also occur at wounds (FLIES?) * Always suspect sarcoids with chronic non-healing wounds * Transmission most likely through biting/rubbing, fomites or insect vectors (FLIES?) * DNA from both BPV 1 & 2 can be identified in both flies and sarcoid tissue * Genes E5, E6 and E7 expressed in sarcoids are capable of neoplastic transformation; however, whole viral particles are not produced

Answer 7

**Occult (flat):** very superficial, often just a ring of altered pigment with focal alopecia extending to scaly/hyperkeratotic skin **Nodular:** well circumscribed within the dermis or subcutis. Overlying skin appears normal initially but can become ulcerated or traumatised. **Verrucose (warty):** raised, hyperkeratotic and resembling papilloma (but any “wart” on a horse is a sarcoid unless proved otherwise). Generally slow-growing. **Fibroblastic (“proud flesh”-like):** raised, ulcerative, and generally aggressive and extensive. Can be pedunculated. Can be bleeding. Only one that does not have a dermal covering over it, it is ulcerated. **Malevolant (“malignant”):** often occur at the sites of wounds or trauma. Aggressive and deeply invasive with lymphatic spread and ulcerated nodules/ Extension of sarcoid under skin surface **Mixed:** two or more different types

Answer 8

**Occult (flat):** very superficial, often just a ring of altered pigment with focal alopecia extending to scaly/hyperkeratotic skin

Answer 9

**Nodular:** well circumscribed within the dermis or subcutis. Overlying skin appears normal initially but can become ulcerated or traumatised.

Answer 10

**Verrucose (warty):** raised, hyperkeratotic and resembling papilloma (but any “wart” on a horse is a sarcoid unless proved otherwise). Generally slow-growing.

Answer 11

**Fibroblastic (“proud flesh”-like):** raised, ulcerative, and generally aggressive and extensive. Can be pedunculated. Can be bleeding. Only one that does not have a dermal covering over it, it is ulcerated.

Answer 12

**Malevolant (“malignant”):** often occur at the sites of wounds or trauma. Aggressive and deeply invasive with lymphatic spread and ulcerated nodules/ Extension of sarcoid under skin surface

Answer 13

Mixed: two or more different types

Answer 14

**Surgical removal** Sharp excision - smaller sarcoids (e.g. nodular) but failure rate high **Laser excision** --\> higher success rate --\> now widely available **Ligation** Some owners will use hair tails – NOT a good plan! DON’T use unless you are sure there is no root Elastrator rings useful for some nodular and pedunculated fibroblastic sarcoids **Cryosurgery** Only useful for small superficial tumours (need to freeze/thaw tissues Time-consuming, and high-recurrence rate if not used effectively **Immuno-therapy** BCG injection into the lesions can be effective for peri-ocular nodular or fibroblastic lesions Does not work for verrucose or occult lesions Not currently available to vets in UK **Chemotherapy** Intra-lesional injection of cytotoxic drugs --\> cisplatin, mitomycin C, 5-fluoro-uracil Can be effective but significant dangers to surgeon: not recommended Topical 5-FU can be effective **Photodynamic therapy** Application of chemical to lesion ----\> significant cell damage when exposed to a certain wavelength of light Poor penetration - only applicable to very small, superficial lesions, side-effects when animal exposed to sunlight **Topical cytotoxic therapy** AW5-LUDES (“Liverpool cream”) contains 5-FU and other heavy metals Reasonably effective in certain circumstances, requires repeated topical application every 48-72 hours Only available through Derek Knottenbelt Health and safety concerns Vaseline over the normal skin before application Everything else (imiquimod, acyclovir, bloodroot ointment, bleomycin, topical mitomycin C, tazarotene….) **Radiotherapy** Iridium wires no longer available in UK High dose rate brachytherapy - very high activity iridium 192 source, emits primarily gamma radiation – catheters implanted into lesion; source driven through catheters by remote afterloader, treatment takes only a few minutes and is delivered in two fractions a week apart – horse not radioactive between treatments, no operator exposure Excellent cosmesis and success around 95%, but expensive (£3800 -£4800 dependant on lesion size , available at AHT only for periocular lesions Treat early for best results!

Answer 15

* Common, but only seen in young horses (\<3 years old) * Warts/verrucae,/“grass warts” often on muzzle or lips * Less commonly on eyelid, external genitalia and distal limbs * Initially small 1mm diameter raised grey/white papules followed by rapid growth to multiple hyperkeratotic lesions up to 2cm in diameter * Numerous keratinous projections * Typically respond spontaneously * Other treatments included autogenous tumour vaccines * Viral aetiology (equine papillomavirus, a DNA papovavirus) * Is contagious and therefore appropriate isolation may be required * Potentially contagious as it is a virus

Answer 16

**Aural plaques** * Common disease of adult horses * Ear papillomas * ? Fly transmission * Almost always an incidental finding * However, rarely, if ever, regress * Cosmetic problem only * DO NOT attempt treatment * Many anecdotal/isolated case reports have been attempted * Extremely variable and generally result in localised pain and discomfort

Answer 17

Third form of cutaneous viral papilloma is equine genital papilloma * Older horses, do not regress * Probably precursors to some genital squamous cell carcinomas

Answer 18

**Melanoma** * **A grey horse disease?** * Any skin mass could be a melanoma * Any unexplained disorder could be a melanoma * All grey horses will get them eventually! (Reassure owners they are not the same as human melanomas but they can/will become pathologically malignant) * Common sites include perianal region, parotid salivary gland, sheath…. and guttural pouch * Altered melanin metabolism results in hyperplasia then subsequent malignancy * Typically, but not exclusively grey or white horses * Middle aged to older horses * Do not confuse with rarer melanocytoma (melanocytic nevi) * Benign and no coat predilection, surgical excision curative * Usually young horses

Answer 19

* Benign neglect/monitor * Standard approach but all lesions will progress * Cimetidine? * Evidence is contradictory * Surgical removal * Wide surgical excision required for larger lesions * Intra-lesional treatments * Cisplatin, mitomycin C (health and safety concerns) * Vaccines/immunotherapy?? * Vaccine-based therapy available but expensive (approx.£2000 for initial course, then £500/vaccine thereafter and unproven although reports of 50% success rates

Answer 20

**_Eosinophilic granuloma_** * Nodular lesions commonly in the saddle area * Precise cause and pathogenesis unknown * Often occur in spring and summer so often attributed to fly hypersensitivity or atopic dermatitis * Other authors suggest trauma * Often called collagen necrosis or similar names although not entirely accurate histopathologically **_Treatment_** * Intra- or peri-lesional steroids (methylprednisolone or triamcinolone) * Systemic steroids (prednisolone or dexamethasone) * In an annoying place on dorsum under saddle

Answer 21

**Squamous cell carcinoma** * Malignant neoplasm of keratinocytes * Can spread either along lymphatic chains or by direct transplantation * Sites: face, eyelids/cornea/globe, genitalia * Can occur anywhere but typically at mucocutaneous junctions * Risk factors: susceptibility to UV light, smegma? * Second most common cutaneous tumour * Most common tumour genitalia * Also common periocular lesion, esp third eyelid * Common in pink skinned horses * Smeg is risk factor.

Answer 22

Treatment dependent on location Surgical excision e.g. * Third eyelid excision * Penile reefing/distal phallectomy/en bloc penile resection Brachytherapy (brachy=short) * Iridium-192 very effective for periocular lesions * Plesiotherapy- Strontium-90 (ß-emmitter) useful for small lesions and corneal lesions (probe 0.8cm D) * Both only available at AHT and are expensive Chemotherapy * Cisplatin, 5-FU can be effective * Mitomycin-C (an antibiotic with anti-neoplastic activity can be good for occular) has been shown to be effective topically and intra-lesionally, often in conjunction with surgical removal NSAIDs * e.g. piroxicam has been used in isolated case reports

Answer 23

Melanoma rostral, Squamous Cell Carcinoma caudal and top lid a nodular sarcoid.