Derm Flashcards
T or F: Dogs and cats can make Vitamin D in their skin
FALSE- No they cannot! Little 7-dehydrocholesterol is found in
the skin of cats and dogs (and likely other carnivores), and
therefore little vitamin D is produced in the skin – that is
because they have high enzymatic activity of 7DH reductase
which converts 7-dehydrocholesterol into cholesterol, reducing
concentrations of this vitamin D precursor in the skin and
preventing its conversion to cholecalciferol
T or F: The diagnosis of Demodex sp. requires histopathology
FALSE- no you
can obtain a diagnosis via SKIN SCRAPING easily! (this diagnosis
should not require histopathology)
T or F: Secondary lesions (crusts) are not diagnostic
FALSE- they ARE! Don’t
scrub or clip them off!
T or F: It is best to biopsy before the use of therapy or after an
appropriate withdrawal period
TRUE
Your colleague asks your opinion on a 10 year old white
cat that has had ulcerated/crusty ear tips for some time
and now has enlarged submandibular lymph nodes.
What tumor would be at the top of
your list?
Squamous cell carcinoma
T or F: Most tumors in the perineal region are benign, castration and surgical
removal will be curative
FALSE- there’s malignant and benign ones – the
benign ones are derived from the perianal hepatoid glands (modified
sebaceous glands); the ones from the anal sac are apocrine in nature and
most are malignant!
T or F: apocrine gland anal sac adenocarcinoma are mostly locally infiltrative and nothing to worry about
FALSE- no, this is definitely a ”need to WORRY” cancer, again yes locally infiltrative but claim to fame is
WIDESPREAD METASTASIS quick
What is a common senile change in dogs?
sebaceous nodular hyperplasia
You notice a tumor that appears to arise from the anal sac on physical
examination of a 7 year old intact male dog. What should next steps be?
biopsy with staging (abdominal and thoracic
radiographs)
Three year old horse with verrucous to nodular, firm,
lesions that has appeared to grow over the past few
months on the face. What is most likely tumor type?
Sarcoid - Most common neoplasm in the
HORSE! Often on the face
6 year old dog presents to you with
bilaterally symmetric, non-pruritic
alopecia, in addition to firm,
thickened, sometimes gritty
ulcerated and alopecic plaques. The
dog also has a pendulous abdomen
and reported to be polyphagic by the
owner.What disease should be at the top of
your list?
Hyperadrenocorticism
5 year old, high-energy dog with year-round
allergies that is crated for long periods of time
during the day. Single lesion that started out as
a plaque and over time progressed to a nodule,
and then most recently became ulcerated.
* A. This is probably a case of acral lick dermatitis
* B. This is Vitamin A responsive dermatosis
* C. This is pemphigus foliaceus
* D. This is probably a drug-reaction
A. Acral Lick Dermatitis
A group of young piglets have been fighting and then shortly after develop exudative dermatologic lesions; some of the piglets have died.
What is your highest clinical suspicion?
Staphylococcus hyicus
7-year old dog with a history of vesicles that quickly progress to striking
ulcers in the oral cavity and a few areas of skin (with crusting). You suspect:* A. Pemphigus foliaceus
* B. Epitheliotropic lymphoma
* C. Pemphigus vulgaris & Bullous Pemphigoid
* D. Discoid lupus erythematosus
Pemphigus vulgaris (PV) & Bullous Pemphigoid (BP) – Correct! BP results in dermalepidermal
clefting, ulceration, which includes oral cavity and MCJs lesions!! Oral mucosa
almost always a presenting complaint with PV.
5-year-old mostly outdoor male castrated cat
presents with the following lesions in the
inguinal fat pad region. These lesions are
nodular and have multiple draining tracts. Your
highest clinical suspicion is that this is what?
Atypical mycobacteriosis - groin overlying inguinal fat pad is the MOST COMMON SITE (site is a tip-off!); wound
contamination or traumatic implantation, nodular and draining tracts
5-year old mixed breed mare presents to you with a history of
being turned out on pastures with standing water in a
tropical/subtropical climate. What is your top differential?
Pythium insidiosum – oomycete, standing water,
ulcerative and proliferative (limbs & trunk) – KEY here is the standing water, tropical/subtropical climate
6-month old puppy with lesions starting out on the face and legs and then progressed. You
perform a skin scraping and find cigar-shaped mites. What is your diagnosis?
Demodicosis - would see scaly, alopecic areas throughout the body, together with a skin scrape showing the classic cigar shaped Demodex mites
Pig with red roughly rhomboid shaped areas on skin. What is most likely cause?
Erysipelothrix rhusiopathiae- can cause a septicemic disease resulting in cutaneous infarcts that are
rhomboidal in shape, diamond skin disease.
A cat presents with circular lesions under the upper lip. What is the top differential?
Hypersensitivity response- indolent ulcer is one of the manifestations of food, flea
allergy, and atopy in cats
What are 3 important functions of skin?
Pigmentation, Vit D synthesis with sunlight (not in dogs and cats!) and barrier to fluid/electrolyte loss
What cells are responsible for pigmentation?
Melanocytes, melanin granules
What is the keratinized layer of the skin called?
Stratum corneum
What separates dermis and epidermis and is important in immune mediated skin disease?
Basement membrane
What connects keratinocytes together and what happens when these are targeted in immune-mediated skin diseases?
Desmosomes, keratinocytes separate and epidermis falls apart- get breach in barrier function
For skin biopsies, what are the main do’s (3) and don’t (1)?
DO: collect multiple sites, Include CRUSTS, Biopsy before therapy- non treated lesions!
DON’T: surgically prepare site before taking samples
What are the 5(.5) types of round cell tumors?
Lymphoma, Transmissible Venereal Tumor, Mast Cell Tumors, Plasma Cell Tumors, Histiocytic Tumors, +/- Melanoma because it can look like anything
What is a common non-neoplastic and/or hyperplastic epithelial tumor?
Skin tags aka acrochordons. Dogs > Cats.
What is a common benign neoplastic epithelial tumor? Characteristic presentation? Prognosis?
Viral papilloma. Exophytic mass on muzzle/face of young animal that may spontaneously regress.
What is a common malignant neoplasm of epidermal cells?
Squamous cell carcinoma.
What are characteristic predilection sites/risk factors for Squamous cell carcinoma? Prognosis?
Solar damage, lack of hair/pigment. Proliferative to ulcerative non-healing lesions. Classic is older white cat with crusty ear margins or dog with subungual tumor. Locally aggressive.
What is a common apocrine gland tumor in dogs? Prognosis? Sequelae?
AGASACA. Most common malignant neoplasm in perianal region of dogs. Highly metastatic. Paraneoplastic hypercalcemia of malignancy due to secretion of PTHrp.
What is a common mesenchymal skin tumor which is non-neoplastic? Defining characteristics?
Harmartoma. Either “scrambled” skin or “dermis on crack”
What is the most common skin tumor of horses? What type of cells?
Equine sarcoids. Tumor of mesenchymal origin.
What is predisposing factor and typical signalment for equine sarcoids? Cause?
Areas of wounds/trauma. Typical signalment: Young horse. Associated with Bovine papillomavirus
What is prognosis for Equine sarcoids?
Locally invasive and recurrent. Goes deep. Hard to excise. Spindly cells.
What is the most common MESENCHYMAL tumor of cats? What are the 2 common clinical manifestations? Prognosis?
Fibrosarcoma. Spontaneous or injection-associated. Locally aggressive.
Which is more aggressive, spontaneous or injection-associated sarcomas?
Injection/vaccine-associated sarcomas are more locally aggressive than spontaneous. More difficult to excise and recur commonly.
What is the dog counterpart to feline fibrosarcoma? Prognosis?
“Soft tissue sarcomas”. Locally invasive.
What are the characteristics of a lipoma?
Benign, expansile, greasy freely moveable, older dogs. Cytology shows adipose cells. Bulges on cut surface.
What are the two types of cutaneous vascular tumors? Cells or origin?
Hemangioma, Hemangiosarcoma. Endothelial cells.
Predilection factors for hemangioma?
Dogs, sunlight exposure.
How do you differentiate hemangioma from hemangiosarcoma?
Histology, staging.
How is cutaneous hemangiosarcoma related to multicentric disease in dogs?
Cutaneous tumors are usually solitary and not part of the multicentric syndrome that involved spleen, lungs, liver and right auricle. They are usually less aggressive, but should still biopsy and stage.
What does cutaneous lymphoma/Lymphosarcoma look like? What species do we see it in? Prognosis?
HIGHLY VARIABLE. Nodules, plaques, might just look like dermatitis. Could just be change in pigment in an area. Cats/Dogs. Slowly progressive. Malignant form is Epitheliotropic lymphosarcoma (“mycosis fungoides”).
What is the most diagnosed malignant skin neoplasm in dogs? Gross manifestation?
Mast Cell tumor. Highly variable. Can wax and wane in size. Can be ulcerated, pruritic, erythematous.
What is the prognosis of a mast cell tumor?
Variable. Most prognostic tool is clinical staging. Need a pathologist to examine margins and grade.
Which are more aggressive: cutaneous mast cell tumors or subcutaneous mast cell tumors?
Cutaneous more aggressive, Subcutaneous less aggressive.
What is prognosis of a feline mast cell tumor?
Less common in cats and majority are BENIGN.
What are the 2 types of subungual tumors in dogs?
Squamous cell carcinoma and melanoma
What anatomical sites of cutaneous melanomas have the worst prognosis in dogs?
Oral cavity, mucocutaneous junction of the lip, subungual.
What is typical signalment for a plasma cell tumor (cutaneous plasmacytoma)?
Older dog.
What is typical prognosis for a cutaneous plasmacytoma? What would be clues that it is not a typical plasmacytoma?
Usually benign single nodular masses confine to the skin. If there is monoclonal gammopathy or hypercalcemia, multiple myeloma is more likely and should be investigated.
What is the typical signalment for a histiocytoma? Prognosis?
YOUNG dog. ONLY dogs. BENIGN and usually spontaneously regress.
What is the typical signalment for a histiocytic sarcoma? Prognosis?
Bernese mountain dog, aggressive and fatal if not completely excised early in progression.
What species are cutaneous endocrine disorders common in?
Dogs
What are the common general endocrine dermatoses?
Bilaterally symmetrical, non-pruritic truncal alopecia. Just tell you that it is endocrine, not specific.
What are the hallmarks of HYPOTHYROID dermatosis in dogs?
General changes (Bilaterally symmetrical, non-pruritic truncal alopecia), plus rarely myxedema
What are the hallmarks of HYPERADRENOCORTICISM dermatosis in dogs? What are signs caused by? Other key signs?
Excess glucocorticoids cause general endocrine pattern (Bilaterally symmetrical, non-pruritic truncal alopecia) plus thin skin, pendulous abdomen and CALCINOSIS CUTIS. GRITTY. PU/PD, stress leukogram.
What are the primary and secondary cornification (hyperkeratotic) disorders?
Primary seborrhea, Ichthyosis, Zinc-responsive dermatosis, Vitamin-A responsive dermatosis, Acral-lick dermatosis, Secondary seborrhea due to hypothyroid, ectoparasites, allergies, etc.,
What signalment or history might suggest a specific hyperkeratotic disease since they all look scaly?
Young animal suggests primary seborrhea.
Scales, impaired barrier function, and secondary bacterial infection suggests ichthyosis.
Huskies/Malamute puppies with scaling around the mouth suggests Zinc-responsive dermatosis.
Young cocker spaniels with generalized crusting/scaling suggests vitamin-A responsive dermatosis.
A single lesion on an extremity of a dog who has been licking/chewing skin suggests acral lick dermatosis.
What is an immune-mediated epidermal disease?
Pemphigus foliaceus
What are the key features that would make you lean towards a diagnosis of pemphigus foliaceus?
PUSTULES with crusting after rupture. FACE esp nasal planum, periocular. Striking BILATERAL SYMMETRY.
What is the cause of PF? How do you diagnose it? What is another differential for pustular skin disease?
Autoantibody to desmosomes, detached, free keratinocytes. Histology of pustules/crusts will show free keratinocytes. Have to rule out pyoderma.
What is the trigger for Erythema Multiforme? What species is this most common in? Clinical presentation?
Proposed triggers: Drugs, infections (viral), neoplasia, dietary substances, vaccinations, but most cases are idiopathic. Dogs primarily. Typically acute onset, erythematous lesions on trunk/axilla/groin.
What is the trigger for Toxic Epidermal Necrolysis? Clinical presentation? Why is this an emergency?
Drug eruptions. Sometimes infections. Full-thickness necrosis and skin sloughing. Issues: fluid loss, sepsis.
What is the trigger for superficial necrolytic dermatitis? Typical signalment? Clinical presentation?
Deranged nutrient metabolism secondary to Hepatic dysfunction, DM, etc. Reduced blood levels of AAcids. Older dogs. Thick crusts and scales that are very dry on footpads. Common to have secondary yeast and/or bacterial infections – STINKY.
What are the gross, microscopic, and clinical presentation of Sarcoptes scabiei infection?
ZOONOTIC. Pigs, dogs. Intense pruritus. Esp sparsely haired skin. Crusts to scaly. Mites burrow in keratin layer and can be found via skin scraping, but in small numbers so may not be found at all.
What is the causative agent of dermatophilosis? What type of organism is it? Morphology on histo?
Dermatophilus congolensis Gram + branching coccoid bacterium. RAILROAD TRACKS.
What are predisposing factors to dermtophilosis? What is most diagnostic sample?
Horses, cattle, sheep mostly. Young or immunosuppressed. Moist environments, wet weather, epidermal irritation from ectoparasites, trauma. Lesion usually on dorsum, extremities. Most diagnostic is THE CRUST.
What are the 2 disease categories that affect the epidermal/dermal interface? In general what causes this group of diseases?
Lupus Erythematosus (Discoid DLE is localized cutaneous form and Systemic SLE is multi-organ form) and the Vesiculobullous diseases. Immune-mediated (or inherited)
Within the Vesiculobullous skin diseases, which presents differently than the rest? What causes this disease and what are the key clinical signs?
Discoid Lupus Erythematosus (DLE) presents differently than the other immune-mediated diseases. DOGS. Immunoglobulins deposit at the BM. Key CS: DEPIGMENTATION of nasal planum/dorsal surface of the nose. Loss of cobblestone appearance of nose. Does not usually affect mucosal surfaces.
What are the similarities and differences between Discoid and Systemic forms of lupus erythematosus?
Both diseases involve autoantibodies against tissue and are most common in dogs. Discoid is localized and cutaneous- immunoglobulins are deposited at the basement membrane between dermal and epidermal layers of the skin. Systemic is a multiorgan disease where antibodies recognize many tissues, including skin.
What signalment and gross findings would tip you off to consider immune mediated vesiculobullous diseases as a clinical differential?
Could affect any species. Immune-mediated forms more common in older animals. Hereditary form is present at birth or in young animals. All characterized by vesicles and ulceration of skin and mucosal surfaces.
Name 2 vesiculobullous diseases
Pemphigus vulgaris, Bullous Pemphigoid, Hereditary or Acquired Epidermolysis Bullosa
What is the general clinical appearance of bacterial disease of the skin? How does the bacteria get into the skin?
Granulomatous or pyogranulomatous inflammation appearing as NODULES. Traumatic implantation of organisms into the dermis or epidermis.
What are the main agents of Bacterial dermatitis? How would you differentiate them?
Staphylococcus, Streptococcus, Actinomyces, Nocardia, Mycobacteria. Have to biopsy to differentiate because they all look the same grossly.
What is atypical mycobacteriosis?
CATS wound contamination/traumatic implantation of saprophytic agents in the inguinal fat pad region.
What is the classic presentation for a dermal abscess? How would you diagnose?
Cat facial skin abscess. Common in cats because of the frequency of puncture wound contamination. Most common agent is Pasteurella multocida in dog and cat bite wounds. Histopath and culture to diagnose.
What dimorphic fungus can cause disease specifically in the skin? Special considerations when diagnosing this disease?
Sporothrix schenckii- zoonotic disease!! Usually cats -> humans.
Where do you find Sporothrix fungus and how does it get into the skin? What species would you see infection most in?
Saprophytic fungus found in moist organic debris that is traumatically implanted into the skin where it grows. Classic example is poking fingers with rose thorns while gardening. Most often in CATS followed by Large animals.
What are key clinical signs of Sporothrix schenckii infection? Histopath findings?
Most commonly lesions on head and legs. Ulcerated nodules and deep draining tracts. Large numbers of yeasts in the cat!
What dimorphic fungi can cause systemic fungal disease and can uncommonly manifest as cutaneous lesions? What do cutaneous lesions look like and how do you diagnose them?
- Blastomyces dermatitidis
- Histoplasma capsulatum
- Coccidioides immitis
- Cryptococcus neoformans
NODULAR areas of GRANULOMATOUS/PYOGRANULOMATOUS inflammation. Cytology/histology to diagnose.
What is classic presentation of Cryptococcus neoformans in cats? How do the organisms look microscopically?
In cats, intranasal disease can spread to skin of muzzle. Super thick mucoid capsule appears as white space surrounding yeast in cyctology/histology.
What oomycete can cause skin disease? Key findings that would make you suspect this?
Pythium insidiosum Warm climate, Standing water exposure, lesions on limbs and trunk, HORSE or DOG
What is a unique gross feature of pythiosis in horses? What are other differentials for this finding?
Kunkers: Yellow, gritty and friable fragments of necrotic tissue and hyphae that dislodge from the lesions. Must differentiate from Habronemiasis by ELISA, culture, or PCR.
What skin disease do horses get in the summer that is caused by a parasite?
Equine Cutaneous Habronemiasis (“summer sores”)
What is the causative agent of Equine Cutaneous Habronemiasis? What is pathogenesis of disease? Presentation/clinical signs? Differentials?
Nematode larvae of Habronema sp. deposited on the skin by
house or stable flies. Trauma from fly bite permits larval penetration. Predilection sites: moist areas and
areas of skin trauma: Prepuce, medial canthus of eye, legs. Ulcerated nodular masses with yellow
gritty foci. Granulomatous and eosinophilic dermatitis. Differential- Pythium infection/kunkers.
What are 2 causes of non-infectious dermatitis? How do they present?
Foreign body reaction- intense focal granulomatous to pyogranulomatous inflammation
with giant cells. Would look like a nodule at site of trauma.
Juvenile cellulitis (juvenile pyoderma, “puppy strangles”). Uncommon, sterile pyogranulomatous dermatitis of head in PUPPIES 3 - 16 wks. UNKOWN ETIOLOGY. Would look like pustules, nodules, crusting, swelling of a puppy face with no identifiable infectious organisms present.
What are the three major etiologic agents for infectious folliculitis in dogs?
Bacterial: Staphylococcus sp. (S. pseudintermedius most common)
Dermatophytes (fungi): Microsporum sp, Trichophyton sp
Parasitic: Demodex sp.
What is the main clinical sign associated with folliculitis?
Alopecia
What are 2 differentials for skin pustules in a dog?
Bacterial folliculitis, Pemphagus folliacious
What is the pathogenesis of bacterial folliculitis?
Predisposing factors (allergy, seborrhea, immune deficiency) cause normal bacterial flora (usually Staph.) to infect hair follicles causing suppurative folliculitis, papules, pustules, epidermal collarettes, alopecia.
What is the medical word for ringworm? What organisms cause it? Where do they grow?
Dermatophytosis, Microsporum or Trichophyton sp. of fungus. Colonize cornified structures like hair, stratum corneum, claws.
What species get dermatophytosis most? Predisposing factors? Special considerations?
CATS, calves, dogs, horses, etc. Hot/humid climate, young animals, stress. HIGHLY CONTAGIOUS. Microsporum canis infections from cats zoonotic to people.
Clinical signs of dermatophytosis?
HIGHLY VARIABLE. Circular, scaly, crusty, alopecia, peripheral red ring.
Why treat dermatophytosis if it will usually spontaneously resolve?
Takes months to resolve, highly contagious, zoonotic, environmental accumulation.
What is the classic presentation for Demodex infection?
DOG. Usually juvenile-onset, self-limiting. Usually localized form (vs generalized). Scaly, red areas of alopecia on face/forelegs.
Where do demodex come from?
Normal fauna of dog skin in hair follicles/sebaceous glands.
How do you diagnose Demodex? Does finding Demodex mites mean that there is a clinical issue?
DEEP skin scrapings or biopsy- cigar-shaped mites. These are the only mites that are ROUTINELY expected in skin biopsy samples of domestic animals! Issue when there is an identification of LARGE NUMBERS of adult mites or an increased number of immature mites.
What is panniculitis?
Inflammation of the subcutis.
What is post-vaccinal skin disease and how can it manifest?
Common, FOCAL panniculitis and vasculitis in deep dermis/panniculus, resulting in follicular atrophy → alopecia. Often in soft-coated canine breeds (poodles esp.) and cats. Manifests as area of alopecia/nodule at injection site.
What is the causative agent of diamond skin disease? Species affected and gross appearance?
Erysipelothrix rhusiopathiae in SWINE. Cutaneous vascular disease. Gross appearance: Rhomboidal shaped red areas of skin.
What is the pathogenesis of diamond skin disease?
Erysipelothrix rhusiopathiae. Septicemia -> bacterial emboli →localized cutaneous vasculitis -> vascular thrombosis -> necrosis (infarction) of skin -> Rhomboidal shape represents the area of skin no longer receiving blood supply
What is atopy? What species does it affect? What causes it?
A hypersensitivity disorder of the skin. Common, genetically predisposed inflammatory and pruritic skin disease of horses, dogs, and cats. Due to environmental allergens and requires prior sensitization to environmental antigens.
What are clinical signs of atopy?
Pruritic, seasonal problem. FACE, FEET, reddened, self-trauma due to scratching. Secondary infections.
Can you distinguish atopy from food allergy clinically?
NO
What is contact dermatitis and how does it manifest in dogs and cats?
Caused by direct skin contact with offending substance. Can be first time contact or after initial exposure. Usually sparsely haired regions, glabrous skin of abdomen. Red patches, papules.
What is flea bit hypersensitivity and what causes it? How common is it? What are key clinical signs?
An extremely common hypersensitivity in dogs and cats caused by salivary antigens of flea. PRURITIC. In Dogs DORSAL SACROLUMBAR LESIONS.
What is feline eosinophilic skin disease? What are three types and most common clinical presentations?
Cat hypersensitivity. Common in cats. Cat allergies can be focal instead of diffuse.
Feline Eosinophilic Plaque
Feline Eosinophilic Granuloma
Feline Indolent Ulcer (eosinophilic ulcer)
How do you distinguish the three types of feline eosinophilic skin disease?
Feline eosinophilic plaque- intensely erythematous raised plaques with severe pruritis on abdomen and medial thighs.
Feline Eosinophilic Granuloma- LINEAR GRANULOMA, hairless, caudal/lateral thighs.
Feline Indolent Ulcer (eosinophilic ulcer)- Concave ulcer on UPPER LIP, Hole puncher lip.
