What is the difference between a vesicle and a bulla?
A vesicle is <1cm and a bulla is >1 cm.
What pathological processes are usually involved when you see vesicles or bullas?
degeneration/necrosis or inflammation and repair.
What causes vesicles/bullas to form?
keratinocytes break apart and allow fluid to build. Can usually be caused by auto-immune dermatoses, viral infections, chemical irritants, and burns.
What is the difference between a pustule and a veiscle or bulla?
a pustule is a palpable elevation filled with pus.
What pathological processes would be involved in pustule formation?
inflammation and repair.
dried exudate, serum, blood, and scale adhered to the skin surface is referred to as what?
What would cause pustules to form?
What causes could be involved in the formation of crust?
Severe disorders of keratinazation or severe pustular dermatitis. Crust formation can also be secondary to ulcers.
What pathological processes could be involved in the formation of crust?
degeneration/necrosis, inflammation and repair, or disorders of growth.
Can a vesicle turn into a pustule?
Yes, if it becomes infected.
Are papules fluid filled?
No. They are solid elevated masses, less than 1cm in diameter. (i.e. mosquito bite)
When would you refer to a papule as a nodule?
When it is greater than 1 cm in diameter and deeper.
What are plaques?
Coalesced papules, raised epidermis with a flat surface.
What pathological processes could be involved in the formation of papules?
inflammation and repair, disorders of growth, or deposits and pigmentation.
What is this a picture of?
Loss of epidermis with exposure of dermis.
What pathological processes can cause ulcers?
Degeneration/necrosis, inflammation and repair, circulatory disorders, or disorders of growth
Ulcers can be caused by
epidermal necrosis, inflammation (really severe), infarction, or neoplasia.
This is an example of ____.
Scale, also known as dandruff.
What is scale? What is the most common cause of it?
Scale is an accumilation of loose keratinized cells. Chronic dermatitis is the most common cause.
What is this a picture of? What causes them to occur?
Epidermal collarettes. They are a circular rim of scale that occurs secondary to the rupture of a vesicle, pustule, or papule.
What is this? What causes it?
Thickening and hardening of the skin, also known as lichenification. Caused by chronic irritation/inflammation.
What are some things you should when collecting a skin biopsy?
Collect it early, before treatment
Collect multiple samples, range of changes
Should you surgically prep the site before collecting a skin biopsy?
What does St. John’s Wort cause?
Type I photosensitization
What is the pathogenesis of photosensitization?
UV light absorbed by photodynamic chemicals in skin —>free radical damage —> epidermal necrosis of lightly pigmented or sparsely haired skin.
What are the 2 types of primary photosensitization and what causes them?
Type I (exogenous) - caused by drugs or plants containing photosensitive chemicals, St. Johns Wort, lucerne, perennial ryegrass, TMS, quinolones, and griseofulvin.
Type II (endogenous) - caused by porphyria or an inherited deficiensy of proporphyrinogen III cosynthetase which leads to a buildup of porphyrins.
What does secondary photosensitization cause?
poor hepatic clearance of phylloerythrin and toxin release that causes biliary obstruction.
What is this image an example of?
Solar injury. Solar/actinic keratosis is due to chronic UV light exposure.
What are you likely to see with first degree thermal burns?
they affect the epidermis and it is reddened/darkened and necrotic. There will be complete healing.
What would you see with 3rd degree thermal burns?
sloughing of necrotic tissue, followed by granulation tissue. There will be a scar and it can be life threatening due to fluid/protein loss and portal for sepsis.
This affects the full thickness epidermis and dermis, +/- sucutis.
This is an example of what degree thermal burn?
What are common causes of chemical burns? Are most cases mild or severe?
They are caused by body or wound secretions, application of drugs, exposure to acids, alkalies, soaps, detergents, or irritant plants.
Most cases are mild (“irritant”)
Erythema multiforme and toxic epidermal necrolysis are a pathogenesis that include what type of hypersensitivity, and to what cells? Which is the most severe of the two?
Type IV hypersensitivity towards antigens of the surface of keratinocytes inducing apoptosis.
Toxic epidermal necrosis is more severe and involves sheets of apoptotic/necrotic cells resembling a burn.
What usually causes lesion depigmenting?
an immune mediated disease.
Pustules/crust usually form as an accumulation of what?
leukocytes. There is an inflammatory component to the lesion.
What pathogenesis can cause dermatitis with vesicles?
burns, certain viruses (cause cells to lyse in a way that vesicles can form), immune mediated pathogenesis.
What are you likely to see with ealy dermatitis?
edema, erythema, and possibly curst, pustules, or vesicles.
What are you likely to see with the later stages of dermatitis?
scaling, change in oiliness, ulceration, alopecia, lichenification, pigmentary change, fribrosis or scarring
This is an example of ____. Is it superficial or deep?
Pyoderma, superficial (folliculitis).
What is this an example of? What is the difference between this and folliculitis?
deep pyoderma, furunculosis. Furunculosis is inflammation due to a ruptured hair follicle, while folliculitis still has an intact follicle.
What layers of skin does superficial pyoderma involve?
Epidermis and hairl follicles.
What are some predisposing factors for bacterial skin infections?
allergy, disorders of keratinization (seborrhea), immunodeficiency, and anatomic predisposition.
What bacteria is the most commonly seen in bacterial skin infections?
What is this an example of? Does this always have to be treated?
Superficial pustular dermatitis (impetigo). It can be self limiting, but it does respond well to staph treatment.
What is this an example of? What is the pathogenesis of this condition?
Skin fold pyoderma (intertrigo). Pathogenesis: closely aposed skin surfaces —> frictional trauma –>moisture –> opportunistic bacterial infections (usually Staph)
What is this an example of? What is usually the cause? How will it appear grossly?
Pyotraumatic dermatitis (hot spots). It is usually due to self trauma, followed by a bacterial infection. Seen often in flea allergy dermatitis cases. Grossly: will be moist, alopaci, raised, and ulceration/crusting will be seen.
What is this an example of? What usually causes it? Is it a primary pathogen?
Exudative epidermitis (greasy pig disease). It is caused by Staph hyicus. It is usually a secondary pathogen.
What is this an example of? What causes the appearance seen below? Where will you find lesions grossly?
Dermatophilosis. Train track appearance due to the bacteria subdividing longitudinally and transversely. Grossly the lesions will be found on the back or distal extremities.
What are some predisposing factors for dermatophilosis?
we weather in humid climates (“rain rot”), prolonged wetting of the skin/hair/wool which allows penetration of epidermis by “zoospores”
What is this an example of?
Canine superficial spreading pyoderma
What is canine superficial pyoderma? How would you diagnose this?
It is a bacterial infection of the superficial follicles and adjacent skin (something infects a hair follicle and then spreads out). Diagnose by cytology of pustule/crust, wood lamp, fungal culture, or skin scraping.
Pemphigus foliaceous is an autoimmune disease involving what type of hypersensitivity?
type II hypersensitivity.
What is the cause of this lesion?
What is this lesion caused by?
What is something you should do if you see ulcers in livestock?
Look for vesicles!
What is the main differential in vesicular diseases?
What is the only sure way do distinguish between vesicular diseases?
What is the most common cause of ulcerative facial dermatitis in cats?
What is this an example of?
Idiopathic sterile granuloma and pyogranuloma syndrome
What may cause these lesions? How would you diagnose this?
Fungal dermatitis, AKA swamp cancer. Diagnose with culture and PCR
What is the MDx? What causes this?
MDx: pyogranulomatous dermatitis.
Cause: actinomycete mycetomas introduced by a traumatic injury. Can have suppurative exudate and involve bone (lumpy jaw)
Actinomycetes can also cause what?
What causes mycobacterial dermatitis in cats? Can it be grown in culture?
mycobacterium lepraemurium. No! It is an obligate intracellular organism.
What can predispose cats to feline leprosy?
Can you culture the bacteria responsible for opportunistic mycobacteriosis? Who does this affect?
Yes, affects cats and dogs.
What is this? Can it be cultured?
canine leproid granuloma. It is difficult to culture, so PCR may be needed (although histo is effective).
Do you always need to treat canine leproid granuloma? What breeds are mostly affected?
No, it is self limiting in immunocompetent dogs (although can last months). It is mainly seen in short coated breeds, esp. boxers and pitbulls.
What is this an example of? Is it sterile or non-sterile?
Puppy strangles. It is sterile granulomatous dermatitis.
What is this a picture of and is it considered a granuloma?
It is a lick granuloma (acral lick dermatitis). It is not a true granuloma, there are no macrophages coming to the area.
What lesions are you likely to see with chronic skin disease?
lichenification, hyperpigmentation, scaling (secondary seborrhea).
What gross lesions are you likely to see due to self inflicted trauma?
erythema, alopecia, and excoriation.
Lesions due to secondary pyoderma involve what?
papules, pustules, and crust.
Histologically, what are you going to see wth allergic skin disease?
lymphocytic and eosinophilic dermatitis.
What is the distribution of lesions in a dog suffering from atopy? What about food allergies?
you will see lesions on the ventrum, face, and distal extremities. Similar lesions will be seen with food allergies.
What type of hypersensitivity plays a role in atopy?
Type I hypersensitivity to environmental allergens.
Contact dermatitis involves what type of hypersensitivity?
Type IV hypersensitivity. Exposure via direct contact.
Insect bites involve what type of hypersensitivity?
Type I and/or IV. Can be a combo of both.
What is this picture an example of? Who is it commonly seen in?
miliary dermatitis. Seen commonly in cats with allergic skin disease.
***Not a pathological diagnosis***
T/F: indolent ulcers, eosinophilic plaques, and eosinophilic granulomas are examples of diseases commonly seen in cats with allergic skin issues.
False. They are not diseases, they are pattern of lesions seen in cats with allergic skin disease.
What is this an example of? What is causing these lesions?
eosinophilic granulomas. In this case, they are called summer sores and are due to a larval migration of Habronema or Draschia sp.
What is the 2nd most common autoimmune skin disease? What usually induces this/makes it worse?
Discoid lupus erythematosus. UV light induces this disorder/makes it worse.
What is this an example of? What is grossly seen with this disease?
discoid lupus erythematosus. depigmentation, erythema, scaling, erosion, ulceration, and crusting.
T/F: you can always use histology to determine edema
False. Fluid is lost post collection, so histology is only helpful to determine edema caused by increased vascular permeability.
What do you see here? What are the 2 main causes of this?
Petechia and ecchymoses. The 2 main causes are vasculitis or thrombocytopenia.
What is the gross appearance of an infarct?
They are a sharply demarcated geometrical shaped dark red to blue area. They become dry, sunken, and darkened as time goes by.
What are some things that can cause infarcts?
Vasculitis, frost bite, toxins causing extreme vasoconstriction (ergot)
What is seen here? Is there necrosis?
Hemorrhage (infarct) due to E. rhusiopathiae. There is no necrosis yet.
What is this? What type of hypersensitivity contributes to this? What causes it?
Purpura hemorrhagica due to a type III hypersensitivity immune mediated vasculitis.
Cause: Streptococcus equi
This type of infarct is due to exposure to cold temperature and is usually seen in the extremities.
What are these an example of? Why are these different from plaques?
These are wheals. They are transient, unlike plaques which are not.
What causes the formation of wheals? Will biopsies be helpful in this case?
If wheals are seen you know that a blood vessel has released fluid and has become engorged with blood. Mast cells have degranulated and there is vasodilation and increased vascular permeability.
Biopsy will not be helpful. Will just see edema and congestion.
What is the term used for hives that only affect the superficial dermis?
What is the terp used for hives that affect both the dermis and the subcutis?
Urticaria (hives) are due to what type of hypersensitivity?
Types I and III, but mostly type I.
Where is angioedema usually seen?
In the face.
What is this?
Hypotrichosis, which is less than the normal amount of hair.
What are some causes of developmental anomalies?
genetic defects, in utero infections, or in utero exposure to teratogens.
If a dog presents to you with skin that stretches more than normal, what is the dog likely to have?
collagen dysplasia. It means that the collagen has not formed properly
This is a histological sample of what? How can you tell?
Collagen dysplasia. You can tell because there is variation in the diameter and shape of the collagen bundles, as well as a haphazard arrangement of them.
What is this? Is it fatal?
epitheliogenesis imperfecta - the generation of the epidermis isn’t perfect. It can be fatal because the skin plays a huge role in the barrier against pathogens.
What is this called?
What are some disorders that can lead to alopecia?
endocrine disorders, hair cycle abnormalities, excessive grooming, self-trauma, autoimmune diseases, general poor nutrition, hyperkeratosis, and cicatricial alopecia (scar)
In male dogs, symmetric alopecia in conjucntion with enlargement of nipples, pendulous prepuce and attraction of other male dogs suggests what dz?
What do you call an increased thickness of stratum basale and spinosum?
What do you call the increased thickness of stratum corneum?
What disorders is hyperkeratosis typically seen with?
primary idiopathic seborrhea, secondary seborrhea (endocrine imbalances, chronic dermatitis), and zinc responsive dermatosis.
This disorder is an inherited disorder of keratinization or cornification. It is thought to involve hyperproliferation of the epidermis, hair follicle infundibulum, and sebaceous glands. It is seen mostly in cockers, springers, and westies.
Primay idiopathic seborrhea
This disorder is typically seen in arctic breeds as well as in pigs and rapidly growing large breed dogs. Grossly, it will appear as scaling around the mouth, chin, eyes, pressure points and paw pads.
Zinc responsive dermatosis
A group of 2.5 month old feeder pigs are presented with non-pruritic keratinized skin lesions and mild lethargy. One severely affected animal is depressed and anorexic. What treatment is most appropriate for the presumptive dx?
Supplement dietary zinc.
What is likely the cause of this?
Severe zinc deficiency
Sarcoptic mane is an example of ____ seborrhea due to chronic dermatitis.
What is causing the alopecia, hyperkeratosis, and lichenification on this animal? Is it contagious or zoonotic?
Sarcoptes scabiei (this wombat has sarcoptic mange). It is both highly contagious and zoonotic.
You get a young puppy with alpecia, hyperkeratosis, and scale around his face. You do a skin scrape and find the following. What is your diagnosis?
The puppy has sarcoptic mange. You can see the sarcoptes mites burrowed beneath the stratum corneum.
You find the following raised, irregular patch of thickened skin on the elbow of one of your older patients. What do you tell the owner it is?
This is a callus which has developed over time due to chronic friction.
Is this a true neoplasm?
No. This is a collagenous hamartoma.
This tumor is one of the most common tumors in dogs. It is locally invasive and slow to metastasize.
Cutaneous soft tissue sarcoma (aka spindle cell tumors).
What are the various types of cutaneous soft tissue sarcomas?
fibrosarcoma, nerve sheath tumor, malignant fibrous histiocytoma, liposarcoma, and myxosarcoma.
What are the various things that go into the grading system for cutaneous and subcutanous soft tissue sarcomas?
differentiation score, mitotic score, and tumor necrosis score.
What is this and what is it caused by? Is it malignant or benign?
This is a papilloma. Caused by the papilloma virus and it is benign. They spontaneously regress.
What is your Mdx? Why?
cutaneous fibropapillomas. Fibropapilloma because dermal connective tissue proliferates the most.
What is your Mdx? What is the cause?
Mdx: cutaneous fibropapilloma. Cause: herpesvirus
What is the following lesion called? What virus is it caused by?
Equine sarcoid. Caused by bovine papilloma virus. It is the only papilloma virus that is not host specific.
When an equine sarcoid is on your differential, what precautions should you take to make sure that your biopsy does not come back as inconclusive?
Need to take a biopsy of an area that is not ulcerated.
This neoplasm is the neoplasm of epidermal keratinocytes, is really invasive, and results in necrosis and ulceration. It is typically seen in poorly pigmented, sparsely haired, sun exposed areas.
Squamous cell carcinoma.
What is this and what is the likely cause?
bilateral squamous cell carcinoma present in site of chronic fly strike (cause)
The following is extremely common in dogs and has a tan, greasy appearance. Is it benign or malignant?
Sebaceous adenoma. Benign.
This growth is more common in dogs than cats and is benign.
These tumors are benign in cats and horses and can resemble inflammation. They are compposed of round cells and often lots of eosinophils.
Mast cell tumors
T/F: you can grade mast cell tumors using cytology.
False. It is a histological process.
These tumors are of langerhans’ cell origin, they are often found on the head, ears, neck, and distal forelegs. They are often benign and found in mostly young dogs.
What is the name of this neoplasm?
Where are melanomas usually benign in canines? Where are they often malignant?
Benign - haired skin.
Malignant - oral, mucocutaneous, subungual.
In what animals are melanomas almost always malignant?
What is this? What is its pathogenesis?
This is a hemangioma/hemangiosarcoma. It is due to solar radiation.
Which type of cutaneous lymphoma affects T-cells only and can cause ulcerations/plaque/masses or nodules?
epitheliotropic cutaneous lymphomas. These congregate/localize to areas of the epidermis.
What factors influence the production of melanin?
hormones, genes, age, and inflammation.
What do you call an increase in the amount of melanin? In what forms can it be seen?
hyperpigmentation (hypermelanosis). Can see a generalized form and a localized form.
What is acanthosis nigricans?
A generalized form of hyperpigmentation that is a genetic disease affecting young dachshunds.
What would you call the following lesion? What are the two types of this disorder that you can see?
hypopigmentation (hypomelanosis). Can have melanocytopenic (decreased # of melanocytes) and melanopenic (melanocytes are there, but they aren’t making melanin).
What are the 2 causes of hypomelanosis?
congenital (like albinism or piebaldism) and acquired (due to copper deficiency or destruction of melanocytes).
What is the name of this disease? Is this melanocytopenic or melanopenic?
Lethal white syndrome. Melanocytpenic. There just aren’t enough melanocytes.
What is your Mdx? What is the name of the disease?
focal leukoderma/leukotrichia. They have “vitiligo” which is an idiopathic acquired melanocytopenic hypomelanosis.
What is this type of calcification called? What is is usually associated with?
calcinosis cutis. Caused by Cushing’s 99.9% of the time.
Who is calcinosis circumscripta often seen in? Where is it normally seen?
Seen in young, rapidly growing, large breed dogs. It is usually seen over pressure points or at previous sites of trauma/injection.
What is this a picture of? What are you likely to see if you prick it with a needle?
mucinosis. viscous fluid is often let out when pricked with a needle.
When do you typically see mucinosis? What are you likely to see secondary to it?
Mucinosis is typocally seen in Shar-Peis (inherited) and with myzedema with hypothyroidism. Pyoderma can be seen secondary to it.