Skin Pathology Flashcards
What 2 types of skin lesions may be present?
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
Define wheals
- discrete focus of dermal oedema
- eg. those seen with intra-dermal skin testing
Define angioedema
- more extensive wheal
- oedema affecting whole body region
What patterns of inflammation may be seen with skin disease?
- perivascular
- diffuse/interstitial
- nodular
- panniculitis
- interface
How does normal skin differ on a single animal?
- haired skin thinner epidermis
- hairless skinner thicker epidermis
Define hyperkeratosis
^ stratum corneum, accumulation of loose fragments -> scale
Define hyperplasia
^ stratum spinosum (thickening of living cell layer, acanthosis)
What are follicular casts and when are they seen?
Accumulation of keratinous debris around the hair shaft
Define comedo
- dilated hair follicle plugged with keratinous and sebaceous debris
What is perivascular dematitis? How is it classified further?
> 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?
Define papule. Eg of disease that may cause papules?
- solid palpable skin elevation <1cm diameter
- e g. FAD
Define plaque. Which species are these commonly seen in?
- larger, flat-topped elevation caused by extension and coalition of papules
- often seen in horses (viral transmission)
Define pustule
Discrete elevation of the epidermis containing pus (cf. abscess dermal/subcut)
Define abscess
Demarcated dermal or subcutaneous acumulation of pus (cf. pustule epidermal)
Potential causes/pathologies of intraepidermal pustular dermatitis?
> Neutrophilic - pyoderma - sterile disease eg. pemphigus > Eosinophilic - ectoparasite infestation - hypersensitivity
What is erosion?
Decreased thickness of epidermis
What is ulceration?
Loss of epidermis down to dermal layer?
Define folliculitis
- inflammation of follicle
Define furunculosis
- inflammation and destruction of the follicle
+ foreign body reaction
Define crust
accumulation of exudate (dead cells and dried serum) on skin surface
- site of previous acive inflammation, epidermal degeneration, pustule etc.
What does a papule precede formation of? What will this become?
Pustule -> focal crust or epidermal colarette
Which diseases are associated with single lesions?
- dermatophytosis
- cutaneous neoplasia
Which diseases are associated with linear lesions?
- external trauma
- blood vessel, dermatome or congential malformation assocaited
Which diseases are associated with annular lesions?
- peripheral spreading of disease eg. pyoderma or dermatophytosis
What do symetrical lesions indicate?
systmeically mediated disease
What is seen with perivascualr inflammation and what diseases is this associated with?
> 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
What is the most common cause of an expanding ring like lesion in dogs>
Staph
When are comedons often seen?
- demodex
- cushings
- hypothyroidism
What does interstitial derm inflammation indicate?
Diffuse inflammation due to spreading of inflammatory cells from original perivascular patterm
What is seen with interface pattern dermatitis and what does this commonly indicate?
> 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
What does nodular pattern of inflammation indicate? What is seen with this?
- inflam celsl in dense clusters, espeically grnaulomatous or pyogranulomatous dermatitis > cell-mediated responses eg: - FB - acid-fast bacilli - deep fungal infection
What does intra-epidermal vesicular or pustular dermatitis appear as? What causes this?
> 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
What occours with sub-epidermal vesicular dermatitis? Causes?
> epidermis separates from underlying dermis
- newborns with defects in structual proteins -> blistering and ulceration (“mechanobullous disease”)
- acquired autoimmunity against structual proteins
What is folliculutis and what may it be preceded or accompanied by?
- inflammation of the follicle
- perifolliculitis (inflam of adjacent dermis) which may also occour as part of perivascular pattern
What is furunculosis?
- 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
What is atrophic pattern and when is this seen?
- NOT inflammatory pattern
- v size of different components of skin
- most commonly epidermal thinning + small telogen phase follicles due to endocrine disease
What endocrine disorder is seen in “plush coated” breeds?
- castration responsive dermatosis
- > symettrical alopencia and pigmentation
What is colour dilution alopecia?
- form of hair follicle dysplasia
- seen in dogs with blue or fawn dilute hair colour (most common blue dobermans)
