Derm - Non neoplastic skin diseases Flashcards
How many patterns of non-neoplastic pathological changes to the skin are there?
12
What is perivascular dermatitis without epidermal involvement?
Inflammatory infiltrate around dilated superficial blood vessels - hyperaemia
Oedema in the dermis - pallor
What does perivascular dermatitis without epidermal involvement look like?
Urticaria - raised, itchy rash
in what species does perivascular dermatitis without epidermal involvement occur?
Horses and dogs
What is perivascular dermatitis with epidermal hyperplasia?
Inflammation around the blood vessels in the dermis along with thickening and hyperkeratosis of the epidermis extending into the dermis
When does perivascular dermatitis with epidermal hyperplasia occur?
Usually after chronic inflammation
What diseases are associated with perivascular dermatitis with epidermal hyperplasia?
Allergic dermatitis
Sarcoptic mange
Callus
Keratinisation defects
What are histopathological features of type I hypersensitivity reaction?
Epidermal hyperplasia
Spongiosis
Hyperkeratosis
Dermal oedema
What is epidermal spongiosis?
Intercellular oedema - oedema between epidermal cells from vascular exudate
What happens if epidermal spongiosis progresses?
It may rupture intercellular bridges and form a spongiotic vesicle
What are the causes perivascular dermatitis with epidermal spongiosis?
UV associated
Direct - sunburn, primary phototoxicity
Indirect - photosensitisation
What is vasculitis?
When inflammatory cells attack the blood vessel wall leading to a loss of blood supply to that area of skin - ischaemia
What are the signs of vasculitis?
Fibrin deposition in vessels
Inflammatory cells in vessel walls
Perivascular inflammation, oedema and haemorrhage
Pinkness of vessel walls - fibrinoid necrosis
Where is vasculitis often seen?
At the extremities - loss of blood supply leads to necrosis
What is interface dermatitis?
Lymphocytes obscure the dermo-epidermal junction
Associated with thickening/clefting of basement membrane and intracellular oedema
What causes interface dermatitis?
Immune mediated disease - cytotoxic T cells kill the keratinocytes allowing immune complexes to deposit in the basement membrane
What are some causes of nodular to diffuse granulomatous dermatitis?
Macrophages - most common
Lymphocytes
Neutrophils (pyogranulomatous)
Infection - bacterial, fungal, protozoal
What is the difference between a vesicle and a pustule?
Vesicle - when there arent many inflammatory cells
Pustule - when the content is cellular
What are some sites of intraepidermal vesicular-pustular dermatitis?
Subcorneal - superficial
Intraepidermal
Suprabasilar - deep
Follicular external root sheath
How do pustules form?
Breakdown of intercellular bridges allow vesicle formation
Then neutrophils/eosinophils infiltrate
What is the most common cause of pustules in the dog?
Staphylococcus pseudintermedius
What is the most common cause of pustules in the pig?
Staphylococcus hyicus - greasy pig disease
What are some other causes of superficial pyoderma?
Sterile pustular dermatitis conditions eg. pemphigus
Insect bites
What is subepidermal vesicular-pustular dermatitis?
a pustule between the epidermis and the dermis
Associated with autoimmune skin diseases eg. bullous pemphigoid
What disease can cause subepidermal vesicular-pustular dermatitis in dogs?
Mechanobullous disease
What are the 3 stages of skin disease centred on hair follicles?
Perifolliculitis
Folliculitis
Furunculosis
What is Perifolliculitis?
When inflammatory infiltrate surrounds the hair follicle
What is folliculitis?
When cells invade the cell wall to the lumen of the hair follicle
What is furunculosis?
Rupture of the hair follicle
What is deep pyoderma caused by?
Staphylococcus pseudintermedius causing folliculitis to furunculosis
What can the hair shaft cause in deep pyoderma?
Pyogranulomatous dermatitis - hair shaft acts as a foreign body
Where can you find deep pyoderma?
Diffuse or localised eg. anal furunculosis
What is fibrosing dermatitis?
When the normal dermal structures are replaced with granulation tissue post inflammation
What is panniculitis?
Inflammation of the fat
It secondarily involves the deep dermis
What are the 3 forms of panniculitis?
Lobular
Septal
Diffuse
What is the difference between lobular, septal and diffuse panniculitis?
Lobular - multinodular appearance, intracellular inflammatory cells
Septal - Inflammatory cells are seen in the connective tissue between the fat
Diffuse - inflammatory cells everywhere
What is atrophic dermatopathy?
A reduction of normal cutaneous structures eg. hair follicles
What causes atrophic dermatopathy?
A complex collection of endocrine and metabolic diseases
What are the clinical features of atrophic dermatopathy?
Alopecia
Increase/decreased pigmentation
Coarse, dry, dull coat
Secondary keratinisation
What type of follicle is affected by endocrinopathies in atrophic dermatopathy?
Telogen follicles
What endocrinopathies can cause atrophic dermatopathies?
Cushings
Hypothyroidism
Oestrogen related
What are 4 features of atrophic dermatopathy?
Telogen follicles
Sebaceous atrophy
Follicular keratosis
This orthokeratotic epidermis - more keratin with no nucleus
When should you do a skin biopsy?
Suspected neoplasia
Unusual dermatosis
No response to therapy
Vesicles, bullae, erosions, ulcerations
