Dermato Flashcards
A 7-year-old horse presents with generalized symmetrical areas of alopecia, erythema, crusting, and scaling on the face, neck, trunk, dorsum, tail, perineal area, and distal limbs. The lesions are not painful or pruritic. The condition has been ongoing for several months with no clear seasonal pattern. Histopathology shows interface dermatitis with CD8+ T cells.
Which of the following is the most likely diagnosis?
A) Pemphigus foliaceus
B) Cutaneous lupus erythematosus
C) Seasonal allergic dermatitis
D) Bacterial folliculitis
B) Cutaneous lupus erythematosus.
2020 Long-lasting successful treatment of a donkey with cutaneous lupus erythematous with methotrexate
A 17-year-old thoroughbred mare presents with an 8-month history of generalized dermatosis that began in spring. The horse has experienced weight loss and severe oral cavity ulcers. On examination, you observe haemorrhagic vesicles and bullae on the mucosa of the oral cavity, lips, oesophagus, and stomach. Less severe lesions are noted on the muzzle, face, and mucocutaneous areas of the perineum. Multifocal erosions, ulcers, crusts, depigmentation, and mild scarring are also present. Histopathology reveals hydropic and lichenoid interface dermatitis. Congo-red staining is positive with apple-green birefringence under polarized light. Serum protein electrophoresis shows a polyclonal gammopathy, and serum amyloid A levels are elevated.
Which of the following is the most likely diagnosis?
A) Pemphigus foliaceus
B) Bullous pemphigoid
C) Bullous amyloidosis
D) Erythema multiforme
C) Bullous amyloidosis.
2021 Bullous amyloidosis in a horse: first description in veterinary medicine
A 15-year-old grey horse presents with multiple black nodules around the anus and under the tail. What is the most appropriate surgical approach for removing these lesions?
a) En bloc resection under general anesthesia
b) Laser ablation
c) Cryosurgery
d) Circular incisions around tumors under epidural anesthesia
Circular incisions around tumors under epidural anesthesia
2022 Surgical options for the treatment of melanomas in horses
What is the primary limitation of using laser-induced photothermal ablation for treating equine dermal melanomas?
a) High cost of equipment
b) Poor efficacy for small lesions
c) Difficulty in treating lesions thicker than 1 cm
d) Frequent local recurrenceAnswer:
c) Difficulty in treating lesions thicker than 1 cm
Laser photothermal ablation using a 980-nm therapy laser is a practical, non-invasive and readily available modality for treating smaller equine dermal melanomas.
Thickness rather than surface area is the main limitation for a single application.
Laser-induced photothermal ablation of equine dermal melanoma
EVE 2024
Which breed of horse has the highest prevalence of melanomas in individuals older than 15 years?
A) Camargue
B) Lipizzaner
C) Pura Raza Espanola (PRE)
D) Gray Quarter Horse
Answer: C) Pura Raza Espanola (PRE)
Explanation: According to the breed differences data, PRE horses have a 100% prevalence of melanomas in individuals older than 15 years, which is the highest among the listed breeds.
VetClinics 2024
What percentage of gray horses have at least one melanoma by age 15?
A) 52%
B) 66%
C) 75%
D) 80%
Answer: D) 80%
Prevalence in horses older than 15 years:
* Camargue: 68%
* Lipizzaners: 75%
* Pura Raza Espanola (PRE): 100%
* Gray Quarter Horses: 52%
VetClinics 2024
Which treatment for equine melanomas has shown the most consistent success based on the provided information?
A) Electrochemotherapy
B) Surgical excision
C) Betulinic acid
D) Oncept melanoma vaccine
Answer: B) Surgical excision
Explanation: The information states that surgical excision remains the most effective treatment with the strongest evidence base. In a case series of 38 melanomas (4-20 cm), none regrew at the surgical site.
VetClinics 2024
In Lippizaners, how much does each copy of the ASIPa mutation increase the melanoma grade on a 5-grade clinical scale?
A) 0.19
B) 0.3
C) 0.5
D) 1.0
Answer: A) 0.19
ASIPa mutation increased the melanoma grade by 0.19/5 (so homozygotes had a grade 0.38/5 higher than those without this mutation).
In general :
* Horses progress by 1 grade every 3 years (0.3 /year) on a 5-grade clinical scale
* Progression is breed-dependent
VetClinics 2024
Different treatments for melanoma?
- Surgical excision,
- Intralesional : cisplatin, carboplatin, mitomycin C, amblyomin-X,
- Electrochimiotherapy,
- Hyperthermia,
- Radio (poor response)
- Immunotherapy : cimetidine, IL 12-18, autologous vaccines, oncept vaccin (DNA vaccin anti tyrosinase), anti-GD2 and anti-GD3 monoclonal antibodies, DNA plasmid vaccination containing the Streptococcus pyogenes emm55 gene
Other: betulinic acid
Equine Melanoma Updates 2024
DDX disorders of pigmentation
- Lentigo : hyperpigmentation
- Overo lethal white foal syndrome : caused by mutation of endothelin receptor B, myenteric aganglionosis, fatal
- Albinism : rare autosomal dominant gene
- Leukoderma : secondary to trauma or inflammation (onchocerciasis, pressure sore, viral skin disease…)
- Vitiligo : idiopathic acquired depigmentation, without previous trauma. Arabian ++
- Leukotrichia : trauma, inflamm°
- Lavender foal syndrome or Coat color dilution lethal syndrome : rare hereditary in Arabian foals of Egyptian lineage. Various neuro abnormalities
DDx disorders of hair
- Trichorexis nodosa : acquired hair shaft disorder, excess gromming, shampoos, pesticides…
- Alopecia areata : rare idiopathic skin disease, focal areas of alopecia. Histo → lymphoid cell around follicles.
- Hirsutism
- Anagen / Telogen defluxion : stress, fever, systemic illness… anagen → hair loss within days of the insult/drug ; telogen → 2-3 months later
DDx disorder of keratinization (3)
-
Seborrhea : descriptive term for excessive scaling and crusting +/- greasiness
- Primary : rare
- Secondary to dermatophytosis, dermatophylosis…
- DDX : pemphigus foliaceus
- Cannon keratosis : idiopathic, hyperkeratosis of the dorsal skin of cannon bones (hindlimbs ++)
- Linear keratosis : young QH and TB, vertical bands of alopecia and hyperkeratosis on the neck, lateral thorax… DDX : sarcoid.
DDX disorder of collagen (3)
- Hereditary Equine Dermal Asthenia (HERDA) : hyperelastosis cutis → QH, Paint… Genetic mutation of collagen, autosomal recessive mode of inheritance. Loose, hyperextensible skin and wounds.
- Warmblood Fragile Foal syndrome (WFFS) : collagen mutation, inherited autosomal recessive disorder. Thin and friable skin of foals → tearing and ulceration from minor trauma + joint laxity → eutha
- Junctional epidermolysis bullosa type 1 (JEB-1) : French and Belgian Draft Horses → foals with erosion and ulceration of the skin, fatal c°. Autosomal recessive mode of inheritance.
DDX of bacterial skin diseases (4)
- Dermatophilosis : dorsum, face, neck, distal limbs. Painful papules and crusts. Malnutrition ++
- Staphylococcal pyoderma : superficial, when natural skin barrier is compromised (chemicals, dermatophytosis). Painful and pruritic c°, alopecia and crusts.
- Corynebacterium : deep pyoderma, pigeon fever (abscesses of pectoral region), ulcerative lymphangitis.
- Bacterial granuloma : secondary to a wound or surgical incision → inoculation into the dermis, granuloma. Most common → Staph. aureus, Pseudomonas aeruginosa, Proteus spp. E. coli
DDX of viral skin diseases (4)
- Viral papillomatosis : Equus caballus papillomavirus. 2 distinct lesions → warts (young < 4 yo) and aural plaques.
- Vesicular stomatitis : reportable disease, vesicles in the mouth and lips, painful erosions and ulcers.
- Equine Coital Exanthema (EHV-3) : contagious venereal disease. Painful papules, vesicles, pustules and ulcers on the external genitalia of mares and stallions.
- Horsepox : benign viral disease, nearly extinct. Oral, leg, or genital horsepox.
DDX of fungal skin disease (1)
-
Dermatophytosis (ringworm) : most common superficial fungal disease. Trichophyton equinum, T. mentagrophytes, Microsporum gypseum, M. canis. Self-limiting but very contageous. Predisposition : illness, poor nutrition, overcrowding, age (young or old), stress, or excessive bathing.
Alopecia, crusting and scaling +/- prurit. Frequent secondary bacterial infection.
What is the pastern dermatitis ?
Descriptive term used for lesions of varied etiologies that appear on the back of the pasterns. Scaly, crusty, oozing, or crusting lesions, +/- painful.
Usually bacterial infections (multi-bacteria, D. congolensis). Can be associated with photosensitivity, chorioptic mange, or Staph. folliculitis.
DDX of parasitic skin diseases (4)
Pediculosis (lice) : severe pruritus, may cause anemia and severe debilitation.
Mites (acâriens) :
- Mange : pruritic ++, may be associated with secondary bacterial infection
* Chorioptes equi → distal limbs, perineum. Predisposition of draft breeds
* Psoroptes equi → forelock (toupet), mane, tail, trunk
* Sarcoptes scabiei → head, neck, ears
- Trombiculasis (aoutats) : chiggers, red bugs. Papules with a small red dot.
- Straw itch mite (Pyedmotes tritici)
- Dermanyssus gallinae (poultry mite) : feed at night, puritic papules and crusts.
- Demodex (rare)
Ticks : bite injuries, transmission of viral, protozoal, bacterial infections. Otobius megnini (soft ticks) → infest the ear canal, otitis externa. Hypersensitivity to the bites → nodules, urticaria, pseudo-lymphoma.
Nematodes :
- Onchocerciasis : Onchocerca cervicalis lives in the nuchal ligament and produces microfilariae → migrate through the skin around the eyes, face, neck, chest… and ingested by Culicoides. Alopecia, scales, crusts, and plaques.
- Habronemiasis : common nodular skin disease → Habronema muscae, H. majus, Draschia megastoma. Flies are intermediate host. Cutaneous habronemiasis when flies deposit larvae on skin, open wounds, or chronically moist area. Ulcerative nodules in the spring and summer (summer sore), similar to exuberant granulation tissue. Pruritus caused by HS.
DDX of hypersensitivity reactions (4)
Urticaria : caused by dermal mast-cell degranulation and released of histamine, prostaglandins… Edema, papules, prurit.
- Insect-bite hypersensitivity (IBH) : most common allergic skin disease. Allergic responses to CUlicoides and other insects (flies, mosquitoes, midges…). Crusted papules, lichenification, prurit ++. Skin distribution of lesions depends on the feeding pattern of insects → mane, tail, dorsum, ventral midline. Seasonality. Heritable component. Histo → eosino dermatitis.
- Atopic dermatitis : second most common skin allergy. Inherited hyperreactivity to environmental allergens → skin +/- respi disease. Altered skin barrier → allows abs° of allergenic proteins → IgE and cytokines release → itch. Intradermal skin testing.
- Food allergy : immune-mediated adverse reaction to a feedstuff by contact or ingestion. Non seasonal pruritic disease or urticaria.
- Contact allergy : rare. Type IV HS. Most common → insect repellents and parasiticides, small molecules that penetrate the skin. Erythema, swelling, vesicles, papules…
DDX of immune-mediated dermatoses (6)
- Pemphigus foliaceus : auto-immune disease directed against the surface protein of keratinocytes that mediate intercellular adherence (anti-desmoglein 1 and 3) → cell separation leaving a space filled with fluid → pustules, crusting, scaling. Face, legs, abdomen. Histo → acantholytic cells
- Pemphigus vulgaris : less common than PF. Anti-desmoglein 3 Ab at the basement membrane at mucocutaneous junction / mouth. Vesicles, bullae, ulcers.
- Bullous pemphigoid : rare ++. Immune reaction, Ab bind to basement membrane, no acantholytic cell → disrupt the dermal-epidermal cohesion. Crusts, ulcers of mucous membranes that extend through GI.
- Lupus erythematosus (systemic and discoid) : interface dermatitis with linear deposition of IgG at the basement membrane. Bilateral symmetric alopecia, seborrhea, oral ulceration…
-
Immune-mediated vasculitis : inflammatory reaction occuring in the wall of blood vessels → type I and II HS. Classified by inflammatory cell type. Neutrophilic vasculitis → leukocytoclastic vs nonleukocytoclastic. Etiologies : EVA, influenza, Corynebacterium, Strep. equi…
Purpura hemorrhagica → type III HS - Alopecia areata : auto-Ab IgG against anagen hair follicles.
DDX of alopecia (non inflammatory, non pruritic) (7)
- Alopecia areata : auto-immune
- Telogen effluvium : stressful influence, widespread synchronous telogen stage.
- Anagen effluvium : hair shaft breakage
- Seasonal alopecia : idiopathic
- Hypothyroidism
- Follicular dysplasia : mane and tail dystrophy of Appaloosa
- Selenium toxicosis
DDX of purpura hemorrhagica
Vasculitis → type III HS
- Strep equi equi
- Strep equi zooepidemicus
- Rhodcoccus equi
- Corynebacterium pseudotuberculosus
- EIV
- EVA
- EHV-1
- idiopathic
What are the grades of burn injury ?
- First-degree burns : involve only the superficial epidermis. Eythema, edema, painful
- Second-degree burns : involve the entire epidermis. Necrosis, painful
- Third-degree burns : loss of epidermal and dermal components. Non painful, wound infection, septicemia.
- Fourth-degree burns : all the skin + underlying muscle, bone, ligaments
What are the types of photosensitization ?
- Primary photosensitization : when the photodynamic agent is ingested, injected, or in contact → St John’s wort (millerpertuis), clovers, alfalfa, fly sprays, ATM soaps, tetracyclines, sulfonamides, furosemide, phenothiazine.
- Secondary or hepatogenous photosensitization : secondary to hepatic injury, the liver cannot excrete phylloerythrin → accumulation of the photodynamix agent. Pyrrolizidine alkaloids → most common cause of hepatogenous PS.
- Endogenous : aberrant porphyrin synthesis (porphyria), rare congenital form.
What is leukocytoclastic vasculitis ?
Photoaggravated vasculitis : common in horses with white hair and pink skin on their lower limbs. Immune deposits of IgG or complement around the vessel walls.
Role of UV light, drug reaction and staph infection. Painful
Hypothesis ?
Scaling, crusting, and alopecia on face, trunk and limbs → generalized exfoliative dermatitis. Mane and tail are spared.
DDX :
- Sarcoidosis (idiopathic granulomatous disease)
- Dermatophilosis
- Dermatophytosis
- Pemphigus foliaceus
- Seborrhea
- Systemic lupus erythematosus
- MEED
- Toxicosis (arsenic, iodine)
How to diagnose sarcoidosis ?
Sarcoidosis : generalized or localized exfoliative dermatitis +/- granulomatous inflammation of multiple organs.
Skin biopsy → sarcoidal granulomatous dermatitis, with numerous multinucleated histyocytic giant cells (photo).
Spread of disease in lungs, liver, GI, lymphadenopathy.
TT : cortico + omega 3/6 + pentoxifylline.
Variable prognosis
Hypothesis in a 3 yo Standardbred ?
Scaling, crusting, ulcerationand alopecia on the face and coronary bands +/- trunk → generalized exfoliative dermatitis in young horses (< 4 yo). Predisposition of SB.
Accompanied by weight loss, ventral edema, hypoalbuminemia, anemia, leukocytosis and neutrophilia, rare eosinophilia.
Involvement of multiple organs →GI, liver, lungs, LN, kidneys…
DDX :
- MEED
- Sarcoidosis (idiopathic granulomatous disease)
- Dermatophilosis
- Dermatophytosis
- Pemphigus foliaceus
- Seborrhea
- Systemic lupus erythematosus
- Toxicosis (arsenic, iodine)
How to diagnose MEED ?
History + clinical exam + skin and multiple organ biopsies
- Skin biopsy → typical epitheliotropic infiltration of eosinophils and lymphocytes (photo)
- Rectal & duodenum → eosinophilic infiltration → intestinal malabsorption
- Liver, LN biopsies
TT → cortico. Guarded prognosis
Hypothesis ?
Ulcerative lesions in the lightly pigmented skin +/- prurit, pain → photosensitization
DDx :
- primary PS
- secondary PS (hepatic injury)
- Dermatophilus infection (characteristic circular lesions) → excessive inflammatory response in the skin, which can trigger vasculitis upon UV exposure.
Histo : diffuse necrotizing and fibrosing dermatitis
What is the gold-standard for peri-ocular sarcoids ? Which alternatives ? Side effects ?
Radiotherapy is considered the “gold standard” for periocular sarcoids, but its high cost and limited availability are significant barriers.
Strontium plesiotherapy is a locally applied, superficial form of radiotherapy described for the treatment of sarcoids. It appears to be very effective. However, it is only suitable for use in the treatment of very small, superficial lesions due to its limited penetration. It is simple, cost-effective, does not require isolation of the horse, and usually requires only standing sedation, but it has very limited availability.
No significant short or long-term adverse effects were noted apart from local leucotrichia, leukoderma and alopecia.
Strontium plesiotherapy for the treatment of sarcoids in the horse
eve 2020
VetClinics 2024
What is the safety and efficacy of strontium plesiotherapy for the treatment of equine sarcoids ?
Strontium plesiotherapy appears to be an effective and safe method of treating selected sarcoids (complete resolution in all 10 cases).
Longer term follow-up is required to determine the risk of recurrence of treated lesions.
Strontium plesiotherapy for the treatment of sarcoids in the horse
eve 2020
What is the most common tumor of horses ? What are the histologic features ?
Equine sarcoids
Sarcoids are histopathologically characterised by plump (dodu), randomly arranged spindle-shaped fibroblasts within the dermis, mild/moderate atypia, and variable number of mitotic figures, often on the low end.
Histopathology of an excised sarcoid has similarities to that of
schwannomas, exuberant granulation tissue, or other mesenchymal neoplasms.
What is the expected overall response rate using 4 doses of ALVAC-fIL2 for sarcoid treatment ?
Tumor size decreased in 86% of the horses, and the median time to first response was 89 days. Adverse events were minimal and included transient focal inflammation in 2 horses.
ALVAC-fIL2, a feline interleukin-2 immunomodulator,
as a treatment for sarcoids in horses: A pilot study
JVIM 2022
Which histological feature is associated with lower recurrence of equine sarcoids following surgical removal ?
Superficial inflammation was significantly associated with reduced odds of recurrence of equine sarcoids at their original surgical removal site.
It is noteworthy that treatments for equine sarcoids, such as the topical chemotherapeutic agents 5-fluorouracil and imiquimod, probably work by inducing ulceration and active inflammation.
Histological evidence of superficial inflammation is associated with lower
recurrence of equine sarcoids following surgical removal: A follow-up study
of 106 tumours in 64 horses
Vet. J. 2023
What are the papillomaviruses associated with SCC ?
- EcPV2 is thought to cause papillomas of the genitals and SCC of the genitals, oropharynx, and stomach.
- These results suggest EcPV7 could cause a subset of equine penile SCC +/- oropharyngeal SCC. If EcPV7 causes a proportion of equine penile SCC, vaccines to prevent EcPV2 infection may not prevent all equine penile SCC.
- EcPV3, 4, 5, 6 cause aural plaques
Equus caballus papillomavirus Type 7 is a rare cause of equine penile squamous cell carcinomas
Vet J 2024
DDX ?
Urticaria
Frequent causes :
■ Atopic dermatitis (environmental allergy → pollens, molds, etc)
■ Drugs and medications
■ Insect/mite bites or stings
■ Chemical contact (plants, dyes, detergents, soaps,
insecticides, etc.)
Less common causes:
■ Dermatophytes (ringworm)
■ Pemphigus foliaceus (auto-immune skin disease)
■ Stress
■ Vasculitis (including purpura hemorrhagica)
■ Pressure or trauma to the skin
■ Cold
■ Exercise
■ Feed
DDX ?
Alopecia + papules
■ Dermatophytosis (ringworm)
■ Staphylococcal infection
■ Alopecia areata (rare autoimmune skin disease)
■ Dermatophilosis
Hypothesis ?
If seasonal → summer sores (habronemiasis)
Summer sores develop when the larvae are deposited in previously damaged skin or mucous membranes such as the lips, nostrils or genitalia where they cannot complete the life cycle and instead cause a local inflammatory reaction.
The lesions themselves consist of areas of ulceration that usually contain small, gritty, yellow nodules (‘sulfur granules’).
Hypothesis ?
Horse with cutaneous Onchocerca. Note the round area of alopecia on the forehead, which is one of the classic presentations of cutaneous Onchocercasis.
It is important to consider that Culicoides transmits Onchocerca and that the signs of IBH and Onchocercasis overlap. Onchocerca can manifest with alopecia and crusting on the face, chest, and abdomen. One classic lesion is the development of alopecic areas, frequently circular on the forehead of the horse.
VetClinics 2024
Hypothesis ?
Note the alopecia, scaling, and depigmentation.
Insect allergic horse that has developed a mixed bacterial and yeast infection on his face because of prolonged use of fly masks
VetClinics 2024
Hypothesis ?
Atopic horse that manifested his disease with facial pruritus. This horse did not have an insect component and his level of pruritus was significantly lower than most horses with insect allergy.
The alopecic area on his face was a chronic area of rubbing, thus, the skin has some evidence of scarring from previous flares of the disease.
Can also affect limbs → self-trauma
VetClinics 2024
Hypothesis ?
Neck and mane of a horse suffering from insect bite hypersensitivity. Note the circular areas of alopecia consistent with a bacterial infection (Staphylococcal folliculitis) and the broken hairs on the mane.
VetClinics 2024
Hypothesis ?
Insect allergic horse with Staphylococcal pyoderma on his face. Note the multiple areas of circular alopecia consistent with bacterial folliculitis.
VetClinics 2024
How to interpret a positive skin allergy test ?
Allergy testing include serologic tests, enzyme-linked immunosorbent assay (ELISA), radioallergosorbent test , and intradermal testing.
There are normal horses that may have some positive results on allergy test, and horses that are pruritic for other reasons that can also show positive results on an allergy test. Thus, a positive allergy test does not guarantee that the clinical signs are due to an allergy to the tested allergens.
Therefore, the diagnosis of environmental allergy is a
diagnosis by exclusion of other pruritic diseases like infections, mites and insects. Allergy testing is done to figure out what sensitizations the patient has with the intent of formulating ASIT.
What matters the most is that the allergens are not selected based on how high the score is on the test but on how they correlate with the environment and seasonality of the patient.
VetClinics 2024
DDX of eosinophilic folliculitis
Symmetrical pruritic papules, all over the neck, shoulders, chest, lateral thoracic area.
Most common cause → infectious folliculitis
DDX :
■ Bacterial (Staph, Dermatophilus)
■ Dermatophytosis
■ other
Eosinophilic granuloma : papules, nodules symmetrically distributed along the body/trunk, +/- pruritic.
DDX :
■ Infectious granulomas
■ Sterile granulomas
■ Neoplasms (mast cells, lymphoma)
■ Cysts
DDX of acantholytic cells ?
- Pemphigus
- Severe bacterial foliculitis (degenerated neutrophils release proteolytic enzymes)
- Dermatophytosis (Trichophyton equinum)
- Dermatophilosis
Thus, it is critical for clinicians to interpret the finding of acantholytic cells and not immediately jump to the conclusion that all patients with acantholytic cells have
pemphigus.
Etiologies of pemphigus
- Idiopathic
- Trggered by drugs
- Vaccines
- Neoplasia (paraneoplastic pemphigus)
Clinicians are always encouraged to always look for a trigger, whether drugs, vaccines, or cancer anytime pemphigus is diagnosed to increase the chances of a positive outcome for the patient and remove the trigger.
Histopathology of pemphigus foliaceus in a horse. Note the area of splitting right below the stratum corneous and the formation of acantholytic cells, pink epithelial cells losing contact with each other.
Hypothesis ?
Ulcerative lesion in the oral cavity
- Bullous pemphygoid (no acantholytic cells)
- Pemphigus vulgaris
- Toxic epidermal necrolysis or vasculitis (secondary to drugs, infection, or vaccination)
