Dermatopathology Flashcards
What are the 5 main pathological processes in dermatopathology?
- Degeneration and Necrosis
- Inflammation and Repair
- Circulatory Disorder
- Disorders of Growth
- Deposits and Pigmentations
What is the difference between a vesicle and a bulla?
A vesicle is less than 1 cm
A bull is greater than 1 cm
Describe what a vesicle or bulla are?
They are a palpable elevation filled with clear fluid.
What types of things can cause a vesicle or a bulla to form?
Auto-immune dermatoses
Viral infections
Chemical irritants
Burns
What are the 2 major types of edema that cause the formation of a vesicle or bulla?
Intercellular edema: spongiosis
Fluid accumulating between the cells.
Intracellularedema: hydropic degeneration
Lost osmotic balance and the cells are taking on too much water. More common with viral infections b/c the cell is preoccupied with assisting in viral replication.
What are the 3 areas that a vesicle can form in the skin?
- Subcorneal
- Suprabasal
- Subepidermal
What is this?
Pustule
Palpable elevation filled with pus.
A pustule is an infiltration of what?
Leukocytes
What is this?
Crust
Could be: dried exudate, serum, blood, or scale that is adhered to the skin surface.
*Scale=excessive keratin
What causes crust to form?
Severe disorders of keratinization.
Severe pustular dermatitis. Ruptured pustules.
Secondary to ulcers.
What is a papule?
Palpable, solid elevated mass less than 1 cm in diameter.
What are 2 subtypes of papules?
Nodules
Greater than 1 cm in diameter and deep.
Plaques
Coalesced papules.
What is this?
Plaques
Remember these are coalesced papules.
What are the causes of papules?
Infiltrate of inflammatory cells
Infiltrate of neoplastic cells
Epidermal hyperplasia
Deposit of mineral: especially Ca2+
What is this?
Nodule
Remember this is a papule that is greater than 1 cm and deep.
What is this?
Ulcer
Loss of epidermis with exposure of dermis.
Ulcers often start out as an ______.
Erosion
What can cause an ulcer?
Stress….j/k….but yeah probably….
Epidermal necrosis
Inflammation
Infarction
Neoplasia
What is this?
Scale
aka Dandruff
Accumulation of loose keratinized cells.
What causes scales to form?
Disorders of keratinization
Chronic dermatitis
What are these?
Epidermal collarettes
A circular rim of scale that occurs secondary to the rupture of a vesicle, pustule or papule.
What is this?
Lichenification
Thickening and hardening of the skin.
You will also get hyperpigmentation and erythema.
What causes lichenification?
Chronic irritation/inflammation
How would you describe this?
Tan-yellow firm plaque-like mass with an ulcerated surface.
Should point out that ulcers are typically depressed but this is elevated.
How would you describe this?
An area of crust on top of erythematous tissue.
What are 4 things you would **not want to do **when performing a biopsy?
Surgically prep the area
Grasp with forceps: this would crush the cells and skew the morphology.
Biopsy the center of a lesion
Hold out on telling the pathologist any important history or some potential differential diagnosis for fear it would influence pathologists opinion.
What are 4 things you would want to do when performing a biopsy?
Biopsy early prior to treating
Be gentle when grasping tissue
Collect multiple samples if possible
Include the crusts: crusts are precious
Degenerative and necrotic lesions tend to _______.
Ulcerate
However, other pathological processes can do this too.
Degenerative and necrotic lesions become ________ and ______ with time.
Inflammation and repair
Normal response to injury and secondary infections are common.
Primary _________ ________ often lead to degeneration and necrosis.
Circulatory disorders
How would you describe these lesions?
We have edema, erythema, alopecia, ulceration and crusting.
What are some differentials we should be thinking about when we look at these sheep?
The history is that it’s been sunny lately but they’ve been huddling in the shade.
Photosensitization
Dermatophilus
Viral infections: Bluetongue, Pox virus (ORF/Scabby Mouth), Vesicular Disease (FMD/VS)
You take a look at the pasture and see this plant growing; what is this?
How can you r/o what is wrong with these sheep?
St. John’s Wort
Can culture lesions, do a cytological prep, serology for viruses, PCR, or a biopsy.
- The blood work, serum ELISA for Bluetongue, and virus isolation from crust all come back as negative. Histolopathology results show epidermal necrosis and ulceration with etiology unknown and a 2ndary bacterial infection.*
- What is your diagnosis?*
**Photosensitization **from the St. John’s Wort
*Knowing that St. John’s Wort causes Primary: Type I Hypersensitization would explain why the sheep have photosensitization despite trying to huddle in the shade. Animals typically do not overexpose themselves. *
How many types of Primary Photosensitization are there?
2: Types I (Exogenous) and II (Intrinsic)
What is Primary: Type I Photosensitization caused from?
Plants containing photosensitive chemicals
ex: St. John’s Wort, Lucerne, Perennial Ryegrass
What is Primary: Type II Photosensitization caused from?
Inherited deficiency of proporphyrinogen III>>
Cosynthetase>>
Defect in heme synthesis>>
Buildup of porphyrins>>
This causes porphyria: which leads to pink teeth and pale oral mucous membranes.
What is Secondary: Type III Photosensitization caused from?
Poor hepatic clearance of phylloerythrin (product of ruminal chlorphyll transformation.)
Toxins cause biliary obstruction.
Most common in ruminants.
What is the pathogenesis of photosensitization?
UV light absorbed by photodynamic chemicals in the skin>>
Leads to free radical damage>>
Epidermal necrosis of lightly pigmented or sparsely haired skin
How would you treat these sheep that are suffering from Primary: Type I (Exogenous) Photosensitization?
Move them to another paddock with shade and cover and no St. John’s Wort.
Treat the animals with severe lesions which may have 2ndary bacterial infections.
What is this?
Solar injury
Acute UV light leads to a sunburn.
Erythema>blistering/vesicles>sloughing of necrotic skin.
What does chronic solar injury lead to?
Solar/actinic keratosis
You get epidermal hyperplasia and dermal fibrosis and elastosis.
What degree of burn is this?
1st degree burn
What degree of burn is this and why?
3rd degree burn
The full thickness of the skin is effected, no nuclei are present, and fluid has accumulated between the dermis and epidermis forming vesicles. Dry necrotic skin can be observed grossly.
What caused this?
Chemical burn from bleach.
Exposure is direct and must penetrate hair and protective epidermal layers.
What is Erythema Multiforme and Toxic Epidermal Necrolysis?
Pathogenesis though to involve Type IV Hypersensitivity towards antigens or the surface of keratinocytes inducing apoptosis.
Induced via antigenic mimcry from drug administration, underlying infection, neoplasia, and possibly dyes or preservatives in pet foods.
- Causes widespread coalescing erythematous macules that lead to vesicles and ulcers.*
- *Macules in picture.*
What is this?
Pyoderma
“Pus in the skin”–typically bacterial infection is involved.
There are 2 types: Superficial and Deep
~the picture shows superficial spreading pyoderma
What is deep pyoderma?
It affects the deep dermis.
- ex: Bacterial furunculosis*
- Abscesses*
Shown is a dog with deep chin acne (basically like small abscesses), a deep pyodema with bacterial furunculosis
What is this?
Impetigo
Superficial pustular dermatitis
Non follicular pustules will develop into crusts.
Typically develop in prepubsescent puppies that are otherwise healthy.
If this occurs in adults you should be looking for underlying disease.
Typically associated with Staph spp. infections
What is this?
Intertrigo
Skin fold pyoderma
You have 2 closely apposed skin surfaces, frictional trauma occurs, leads to moisture, and trapping of bacteria which in turn leads to infection.
What is this?
Pyotraumatic dermatitis
Hot spot or Acute moist dermatitis
This is very common in dogs.
Typically from self trauma which leads to secondary bacterial infection.
Grossly: Alopecia, slight raised, red, well-circumscribed lesion that leads to ulceration and crusting.
Underlying pruritis: possibly flea allergy.
What is this?
Species is a pig.
Greasy pig disease
Exudative epidermitis
Fatal in neonatal pigs.
Causative agent: Staphylococcus hyicus
Grossly: erythema which leads to pustules and then crust.
Other predisposing factors: other skin lesions, poor husbandry, or nutrition, lacerations, etc.
What is this?
Species is a sheep.
Hard to make a diagnosis based on this image alone.
From the previous picture of a sheep, you do a Gram stain which reveals these organisms….now what is your diagnosis?
Dermatophilosis congolensis
Gram positive filamentous bacteria: characteristic train tracks apperance.
Lesions are typically on the back as we saw, or in the distal extremities.
This bacteria stimulates neutrophilic exocytosis: pustules which leads to exudate, matting of the hair and wool, and subsequent alopecia.
Predisposing factors: wet weather/humid climates: sometimes this is called rain rot or lumpy wool. Prolonged wetting of the skin hair and wool allows penetration of the epidermis by zoospores.
What is this?
Canine superficial spreading pyoderma
Usually this is a secondary condition.
Bacterial infection of the superficial follicles and adjacent skin.
Grossly: there is scaling, erythematous macules (often circular or ring shaped), papules, pustules, crusts, epidermal collarettes and alopecia.
What is this?
Folliculitis (follicular inflammation) and furunculosis (rupture of the follicle)
What is this?
Demodicosis
Although it should be pointed out that this is often indistinguishable from superficial spreading pyoderma.
Cause: Demodex, demodectic mange
Lesions will vary as well as their distribution on body. May be localized in the face or forelegs or more generalized.
Adult onset usually indicates an underlying disease process.
Can be neutrophilic (exudative) to granulomatous (nodular) grossly.
What are the causes of Dermatophytosis?
How do animals acquire Dermatophytosis?
What are some predisposing factors to Dermatophytosis?
Epidermophyton, Microsporum and Trichophyton spp. –keratinophilic fungi
Contact with scales shed from infected animals.
Young or immunosuppressed or Hot/humid environments.
How would we grossly describe these changes?
What is the morphological diagnosis (MDx)?
What would be the etiological diagnosis (EDx)?
Crusting and ulceration periorbitally and around nares, depigmentation and erythema, and pustules present.
MDx: Exudative dermatitis or Pustular dermatitis
EDx: Bacterial dermatitis (suspect: would need to confirm with cytology or biopsy.)
So we get the cytology back on the previous dog and is noted that there is some bacteria but not within the cytoplasm of leukocytes and there isn’t too many neutrophils. The biopsy however reveals this….
What are these cells that the arrow is pointing too and what is this indicating the etiology is?
Acantholytic keratinocytes: keratinocytes that have lost their cell to cell function.
Consistent with Pemphigus foliaceous
What causes this?
We now know that….
Pemphigus foliaceous
is the cause.
Pemphigus is a group of auto-immune diseases involving Type II Hypersensitivity against cell adhesion proteins (desmosomes).
Can be spotaneous, drug induced, or associated with allergic skin disease.
Pigs at a zoo came down with these lesions…
How would we describe these changes?
What would our MDx be?
This pathological process is likely what?
Multiple <1 cm, slight raised and crusted papules and slightly solid.
Papular dermatitis
Disturbance of growth or Inflammatory
Most tests for the pigs showed NSF (no significant findings) except with the biopsy, these were seen [where arrow is pointing].
What is the arrow pointing to and what is this indicative of?
What would our MDx be?
Swollen vacuolated cytoplasm or hydropic change. The cytoplasm is completely clear but it also contains eosinophilic globules which are viral inclusion bodies.
Consistent with: Swine Pox infection
MDx: Proliferative dermatitis with ballooning degeneration and intracytoplasmic inclusion bodies.
What are the sequence of lesions with Pox viruses?
Papule>>Vesicle>>Umbilicated pustule>>Crust>>Scar
If you see this, what should you be thinking?
Pox virus until proven otherwise
Raised papule with a necrotic center.
What is this poor lamb suffering from?
Parapox virus
ORF, Scabby Mouth, Contagious Exanthema
Zoonotic
Early papular to vesicular phase
What is the sheep suffering from?
Parapox virus
ORF, Scabby Mouth, Contagious Exanthema
Zoonotic: below is shown a human hand with ORF: painful papule with an umbilicated center.
Late crusty phase of disease with most likely secondary bacterial infection.
What is this on the foot of a pig?
What is the MDx of what this pig is suffering from?
Vesicle
Just starting to rupture, skin flap lifted up and clear fluid is leaking out.
MDx: Vesicular ulcerative pododermatitis
What is this in the mouth of a sheep?
What is the MDx of what this sheep is suffering from?
Ulcer
MDx: Vesicular ulcerative stomatitis
What is the morphological diagnosis (MDx) of what this cow is suffering from?
MDx: Vesicular ulcerative dermatitis
What is the MDx of what this horse is suffering from?
Mdx: Vesciular ulcerative stomatitis
In the previous 4 slides, the pig, sheep, cow and horse have all been suffering from lameness, anorexia, ptyalism (drooling) and these lesions.
What is the most likely causitive agent?
How would we confirm what the causitive agent is?
Viruses
Early herpesvirus, early poxvirus, or vesicular diseases such as FMD, VSV, SVD, and VES.
Laboratory testing
It turns out that this was VSV~ Vesicular Stomatitis Virus, this affects cattle, pigs, horses and wildlife.
What is this?
Vesicular ulcerative dermatitis in the face of a cat caused by: Feline Herpes Virus- 1
What is this?
A cow with vesicular ulcerative dermatitis caused by Bovine Herpes Virus- 2.
Pseudo-Lumpy Skin Disease
What is this?
A cow with vesicular ulcerative mammillitis caused by Bovine Herpes Virus- 2.
Different strains have different predilection sites.
A 4 year old mixed breed dog has multiple lesions like this:
What is the most likely pathological process?
How would you describe these lesions?
Disturbance of growth (neoplastic cells) or inflammatory (cells; granuloma). We know it’s not an abscess because there is no leukocytes.
Plaques, papules and nodules in multiple foci.
A biopsy was done from the previous papule and here is what was found (no infectious agents or foreign material were seen with special stains):
How would we describe this?
Multifocal granulomatous dermatitis~ sterile
What is this?
Idiopathic Sterile Granuloma and Pyogranuloma Syndrome
- Rare*
- Found mostly in dogs*
- Pathogenesis is unknown*
What is this?
Fungal dermatitis
Pythium, Lagenidium spp.
Swamp Cancer, or Florida Horse Leeches
Pythium insidiosum mainly seen in dogs and horses
Clinically resembles neoplasia, they are very invasive and spread to regional lymph nodes.
