The reaction of skin to injury Flashcards
What are the names for hyperkeratosis where squamous epithelial cells are (A) nuclear and (B) anuclear
(A) orthokeratotic hyperkeratosis
(B) parakeratotic hyperkeratosis
Causes of hyperkeratosis
congenital ichthyosis Vit A deficiency Zinc deficiency Seborrhea Sarcoptic mange Superficial necroltic dermatitis
What is seborrhea?
Nonspecific name for clinical signs of excessive scaling, crusting and greasiness. Has no relevance to actual meaning of “excess flow of sebum”
What’s a hyperplastic disease?
Alteration of epidermal growth and differentiation, characterised by increase in the number of cells
Acanthosis refers to?
Increase in thickness of stratum spinosum
Hyperplasia occurs as a primary lesion in:
Callus
Sarcoptic mange
Actinic keratosis
Hyperplasia is?
thickening of all cell layer except the stratum corneum
Erosion is:
Loss of the superficial portion of epidermis
Ulceration is:
loss of an area of full thickness of the epidermis and portion of the dermis which is exposed
Causes of epidermal necrosis
Physical injury (chemical, burns, radiation)
Chemical
Injury as a result of vasculitis, ischemia and infarction
What is intercellular oemema of the epidermis called?
spongiosis
What characterises ballooning degeneration?
infiltration of fluid into keratinoctyes -> swelling of cells to sphericals -> cell burst and membrane remains in network patter (reticular degeneration)
What is acantholysis?
the disruption of intercellular junctions (desmosomes) between keratinocytes of the epidermis. This process is initiated by damage or defects in adhesion molecules. Usually occurs in immune mediated diseases.
What are vesicles?
fluid filled cavities beneath the epidermis
What is a bulla
a vesicle greater than 1cm
Causes of spongiosis
staphylococcus spp
Malassezia infection
Causes of ballooning degeneration
Poxivirus infection
Herpesvirus infection
Superficial trauma to epidermis
Vesicles occur in
Virus infections
Thermal burns
Some drug and allergic reations
What is a pastule?
Cavities filled with neutrophils (pus)
Causes of pastules
Bacterial skin infection
Pemphigus foliaceus
What is hyperpigmentation?
Increased melanin production
Causes of hyperpigmentation
Chronic inflammatory disease Edocrine dermatoses (hyperadrenocorticism)
Causes of ulcers
Self trauma (excoration)
Disease -> inflammation and necrosis (e.g viral infections. Some immune mediated diseases and burns)
Ischaemia secondary to vasculature compromise (vasculitis)
What are crusts?
dried fluid and cellular debris located on the epidermal surface
Primary crusts
allergic dermatitis
secondary crusts
inflammation, excoriation, ulceration and necrosis, rupture of pastules
Diseases causing ulceration and crusting
Allergic skin disease Greasy pig disease Photosensitization, burns Dermatophilosis Sarcoptic mange Pemphigus foliaceus
Causes of follicular atrophy
hormonal abnormalities (hyperadrenocorticism, hypothyroidism) nutritional abnormalities scar formation (eg following furunculosis or folliculitis, sebaceous adenitis or alopecia areata
Folliculitis
Inflammation of the hair follicle
Furunculosis
rupture of the follicular due to inflammation
Diseases causeing folliculitis/furuncolosis
Demodectic mange
Dermatophytosis (ringworm)
Bacterial infections (straphylococcus spp) with pyoderma
Characteristics of dermal atrophy
Decrease in collaged fibrils and fibroblasts -> decrease in thickness which becomes thin and translucent
Diseases of dermal atrophy
Hyperadrenocorticism (Cushing’s Syndrome)
Hypothyroidism
Congenital collagen defects (Ehler’s Danlos syndrome)
Conditions with Dermal Fibrosis
Scars
Proud flesh
Characterisation of type 1 hypersensitivity reactions
Eosinophils, mast cells, lymphocytes and plasma cells
Diseases with dermal inflammation:
Mycobacteriosis
Insect-bite hypersensitivity
Eosinophilic granuloma in cats
Deep pyoderma as a result of furunculosis
What is Congenital ichthyosis?
Lamellar hyperkeratosis due to increased cohesion of defective dishesion of keratinocytes associated with short epidermal turnover.
Features of congenital ichthyosis
scaling, lichenification and crusting
Callus?
localised, hyperplastic skin reaction to trauma caused by pressure or friction.
what is Actinic Keratosis?
solar induced hyperplastic lesion. Normally on non pigmented and sparsley haired skin.
May progress to squamous cell carcinoma
What is Type I photosensitisation?
ingestion of plant or drug with photoreactive substances
What is Type II photosensitisation?
Animals have genetic inhability to metabolise haem pigments.
What is Type III or hepatogenous photosensitisation?
abnormal buildup of phylloerythrin (product of chlorophyll) due to damaged liver
Lesions of photosensitisation
on non pigmented/hairless skin.
May cause extensive oeedema -> facial eczema
Progression of burns
erythema (redness due to dilation of capillaries) -> erosion -> ulceration -> vesicles due to dermal/epidermal separation.
- In full thickness necrosis the damaged skin becomes firm and dry due to avascular necrosis and eventually sloughs.
What is contagious ecthyma (orf)?
Localised infection of young sheep and goats caused by a parapoxvirus
Gross lesions in orf
vesicle -> pastule -> crust -> scar
What is dermatophylosis?
Caused by bacterium dermatophilus congolensis.
It is a pastular, exudative dermatitis
Gross lesions in Dermatophylosis
raised, alopecic and sometimes papillomatous lesions covered by a thick keratinized crust
what causes Greasy pig disease
Straphyloccus hyicus
Gross lesions of greasy pig disease
the skin is greasy and erythematous with malodorous exudate
Pathogenesis of greasy pig disease
starts as a pastular disease which extends to follicles; the pastules rupture->exudate dries and the crust forms; exfoliative staphylococcal toxins digest desmoglein 1 involved.
