Skin Pathology Flashcards

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1
Q

What 2 types of skin lesions may be present?

A

1* - direct consequence if the disease process
> eg. macule, nodule, tumour, wheal, vesicle, bulla, patch, papule, pustule, comedo, follicular cast, alopecia, scale, crust
2* - evolve from 1* lesion or caused by self trauma (may obscure 1* lesion)
> eg. epidermal colarette, scar, excoriation, erosion, ulcer, fissure, lichenification, hyperpigmentation, callus

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2
Q

Define wheals

A
  • discrete focus of dermal oedema

- eg. those seen with intra-dermal skin testing

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3
Q

Define angioedema

A
  • more extensive wheal

- oedema affecting whole body region

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4
Q

What patterns of inflammation may be seen with skin disease?

A
  • perivascular
  • diffuse/interstitial
  • nodular
  • panniculitis
  • interface
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5
Q

How does normal skin differ on a single animal?

A
  • haired skin thinner epidermis

- hairless skinner thicker epidermis

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6
Q

Define hyperkeratosis

A

^ stratum corneum, accumulation of loose fragments -> scale

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7
Q

Define hyperplasia

A

^ stratum spinosum (thickening of living cell layer, acanthosis)

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8
Q

What are follicular casts and when are they seen?

A

Accumulation of keratinous debris around the hair shaft

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9
Q

Define comedo

A
  • dilated hair follicle plugged with keratinous and sebaceous debris
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10
Q

What is perivascular dematitis? How is it classified further?

A

> stereotypical/classical reaction to a multitude of pathologies! If skin is red and itchy: probably “hyperplastic, superficial, perivasc. derm.”
may be due to allergy/parasites/infection
- prominance of dermal blood vessels
- leucocytes recruited
- usually + epidermal hyperplasia
superficial/deep plexus involved?
predominnat cell type?

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11
Q

Define papule. Eg of disease that may cause papules?

A
  • solid palpable skin elevation <1cm diameter

- e g. FAD

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12
Q

Define plaque. Which species are these commonly seen in?

A
  • larger, flat-topped elevation caused by extension and coalition of papules
  • often seen in horses (viral transmission)
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13
Q

Define pustule

A

Discrete elevation of the epidermis containing pus (cf. abscess dermal/subcut)

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14
Q

Define abscess

A

Demarcated dermal or subcutaneous acumulation of pus (cf. pustule epidermal)

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15
Q

Potential causes/pathologies of intraepidermal pustular dermatitis?

A
> Neutrophilic 
- pyoderma 
- sterile disease eg. pemphigus 
> Eosinophilic 
- ectoparasite infestation 
- hypersensitivity
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16
Q

What is erosion?

A

Decreased thickness of epidermis

17
Q

What is ulceration?

A

Loss of epidermis down to dermal layer?

18
Q

Define folliculitis

A
  • inflammation of follicle
19
Q

Define furunculosis

A
  • inflammation and destruction of the follicle

+ foreign body reaction

20
Q

Define crust

A

accumulation of exudate (dead cells and dried serum) on skin surface
- site of previous acive inflammation, epidermal degeneration, pustule etc.

21
Q

What does a papule precede formation of? What will this become?

A

Pustule -> focal crust or epidermal colarette

22
Q

Which diseases are associated with single lesions?

A
  • dermatophytosis

- cutaneous neoplasia

23
Q

Which diseases are associated with linear lesions?

A
  • external trauma

- blood vessel, dermatome or congential malformation assocaited

24
Q

Which diseases are associated with annular lesions?

A
  • peripheral spreading of disease eg. pyoderma or dermatophytosis
25
Q

What do symetrical lesions indicate?

A

systmeically mediated disease

26
Q

What is seen with perivascualr inflammation and what diseases is this associated with?

A

> inflam cells around dermal BVs (Superficial/mid/deep vascular plexus) VERY COMMON!

  • neutrophils: Self trauma, pyoderma
  • eosinophils: ectoparasites, hypersensitivty
  • mononuclear cells: chronic dermatitis, immunologic causes
27
Q

What is the most common cause of an expanding ring like lesion in dogs>

A

Staph

28
Q

When are comedons often seen?

A
  • demodex
  • cushings
  • hypothyroidism
29
Q

What does interstitial derm inflammation indicate?

A

Diffuse inflammation due to spreading of inflammatory cells from original perivascular patterm

30
Q

What is seen with interface pattern dermatitis and what does this commonly indicate?

A

> dermo-epidermal junction obscured by inflam cells (lymphocytes) and hydropic degneration of basal keratinocytes
less of pigment possible as melanocytes located near basal cells
vesicles/bullae and erosions/ulcers if epidermal cohesion affected
- UNCOMMON, indicates AUTOIMMUNITY against epidermis or DRUG REACTION

31
Q

What does nodular pattern of inflammation indicate? What is seen with this?

A
- inflam celsl in dense clusters, espeically grnaulomatous or pyogranulomatous dermatitis
> cell-mediated responses eg: 
- FB
- acid-fast bacilli
- deep fungal infection
32
Q

What does intra-epidermal vesicular or pustular dermatitis appear as? What causes this?

A

> vesicles and bullae (blisters)
- death of clusters of epidermal cells or loss of adhesion of cells with accumulation of fluid exudate
- seen in viral infection eg. FMD
Pustules
- inflammatory cells predominate rather than fluid
- bacterial infection
+-Acantholysis
- destruction of desmosomal attachments between keratinocytes
- may be enzymatic eg. proteases in pyoderma
- may be autoimmune eg. pemphigus

33
Q

What occours with sub-epidermal vesicular dermatitis? Causes?

A

> epidermis separates from underlying dermis

  • newborns with defects in structual proteins -> blistering and ulceration (“mechanobullous disease”)
  • acquired autoimmunity against structual proteins
34
Q

What is folliculutis and what may it be preceded or accompanied by?

A
  • inflammation of the follicle

- perifolliculitis (inflam of adjacent dermis) which may also occour as part of perivascular pattern

35
Q

What is furunculosis?

A
  • inflammatory DESTRUCTION of the hair follicle -> rupture and extrusion of contents (hair, keratin, sebum, infectious agents) into dermis -> Deep pyoderma
  • 2* FB response often supparative or pyogranulomatous inflammation
  • > scarring or fistula formation and panniculitis
36
Q

What is atrophic pattern and when is this seen?

A
  • NOT inflammatory pattern
  • v size of different components of skin
  • most commonly epidermal thinning + small telogen phase follicles due to endocrine disease
37
Q

What endocrine disorder is seen in “plush coated” breeds?

A
  • castration responsive dermatosis

- > symettrical alopencia and pigmentation

38
Q

What is colour dilution alopecia?

A
  • form of hair follicle dysplasia

- seen in dogs with blue or fawn dilute hair colour (most common blue dobermans)