Skin Pathology Flashcards
What is a primary skin lesion?
A lesion that develops as a direct consequence of the disease process
What is a secondary skin lesion?
Evolve from a primary lesion or are caused by the patient themselves (self-trauma) e.g. ulcer developing from ruptured vesicle
What is a wheal?
A discrete focal dermal oedema
What is angiodema a more extensive version of?
A more extensive wheal affecting a whole body region due to type I hypersensitivity
Describe perivascular inflammation…
Inflammation focused around blood vessels = prominent blood vessels, oedema
Describe diffuse/interstitial inflammation…
Inflammation more widespread in the dermis/epidermis
Describe nodular inflammation…
Dense infiltrates of inflammatory cells in the dermis but arranged in nodules
Describe panniculitis inflammation…
Inflammation of the subcut adipose tissue (often systemic cause)
Describe interface inflammation….
Degeneration of basal keratinocytes due to infiltration of the dermoepidermal junction
How does the anatomy of the skin vary between haired and non-haired animals?
The epidermis is much thicker in hairless animals
Where do the changes in the epidermis occur when you get hyperkeratosis and hyperplasia?
Hyperkeratosis - Increased stratum corneum (i.e increased scale)
Hyperplasia - Increased stratum spongiosum (i.e. thickening of liver cells)
What is scale? Is it a primary or secondary lesion?
Accumulation of loose fragments of stratum corneum. It is considered a secondary lesion due to hyperkeratosis
What are follicular casts and what disease process can they occur in?
Accumulation of keratinous debris around the hair shaft. Can occur due to demodecosis.
What is a comedo? What disease process can it occur in?
Black head caused by dilated hair follicle plugged with keratinous and sebaceous debris.
A common cause is demodecosis, idiopathic seborrhea and endocrine disease
What is a papule?
A solid palpable elevation of <1cm diameter
What diseases may you see papules?
FAD
Staph pyoderma
Scabies
Atopic dermatitis
What is a plaque?
A flat, solid elevation caused by extension or coalition of papules.
What disease processes may cause plaques?
Eosinophillic plaques in cats
Aural plaques of horses (spread by flies)
What is a pustule? How does it differ to an abscess?
A discrete elevation of the epidermis contain pus
An abscess is similar except it is a demarcated dermal or subc accumulation of puss
What diseases might you see papules in?
Canine pyoderma
Demodecosis
Pemphigus
How does the contents of a pustule idicate the aetiology of an intraepidermal pustular dermatitis?
Neutrophils - Pyoderma
Eosinophillic - Ectoparasite infestation
What does a pustule develop into at later stages?
An epidermal collarette (usually staph origin)
What is the difference between ulceration and erosion of the skin?
Erosion - intact basement membrane and so dermis is not exposed
Ulcer - break in basement membrane so the dermis is exposed
Give an example of a disease which may cause skin ulcerations…
e.g. cutaneous lymphoma
What is a crust?
Accumulation of dried exudate on the skin surface at the site of previous inflammation
What particular bad autoimmune disease causes severe crusting?
Pemphigus
What is the definition of a nodule?
A solid palpable skin elevation >1cm
Give examples of diseases that causes skin nodules
MCT
Mycobacterial skin infection
What is the difference between a macule and a patch?
A flat circumscribed area of change in skin colour <1cm in diameter (macule) or >1cm (patch)
What is lichenification and what does it appear like?
It is accentuation of normal skin markings leading to elephant appearance skin.
Give examples of diseases that cause lichenification…
Malassezia
Chronic allergic disease
What is leukotrichia?
Loss of hair pigment
What is folliculitis a powerful pattern for in dogs?
Pyoderma
Dermatophytosis
Demodecosis
