Skin pathology Flashcards
What are the layers of the epidermis?
- statum corneum
- stratum spinocum
- stratum basale
- basement membrane below these
What does the dermis contain?
- vessels
- collagen
- nerves
What is adnexa?
- hair follicles
- sweat glands
- sebaceous glands
What are examples of epidermal responses to injury?
- hyperkeratosis
- epidermal hyperplasia
- malassezia
What is hyperkeratosis?
- =increased thickness of the stratum corneum
- very common feature of longstanding surface trauma
What are the clinical signs of hyperkeratosis?
- dry flaky skin
- scales
What are the diseases/conditions characterised by hyperkeratosis?
- any chronic surface injury
- seborrhea
- zinc deficiency
- endocrinopathies
What is this animal presenting?
- severe hyperkeratosis
What condition is this?
- hyperkeratosis due to zinc deficiency
- very thick layer (epidermis)
What disease does this calf have?
- congenital ichtyosis (fish skin disease)
- hairless skin
- thickened and scaly
What is epidermal hyperplasia?
- increased numbers (therefore layers) of keratinocytes in the epidermis
What is Acanthosis?
- specific term that refers to increase thickness of the stratum granulosm
What is the earliest reaction to skin injury?
- epidermal hyperplasia
What condition is this showing? What are the signs?
- epidermal hyperplasia
- see mild hyperkeratosis
What condition does this dog have?
- long standing duration epidermal hyperplasia = alopecia
What condition is shown here?
- malassezia
- keratinocytes
In what circumstances can epidermal hyperplasia occur?
- occurs in hypersensitivity disorders (allergy)
- e.g. flea bite reactions
- recruits eosinophils and mast cells
What skin condition is shown here?
- lichenification (severe epidermal hyperplasia)
- thickened and leathery skin = exaggeration of the normal skin markings resulting from longstanding surface trauma or friction
What is this and where does it normally occur?
- callus =thickened often pigmented and hyperkeratotic plaque
- hyperkeratosis and hyperplasia at the same time
- tends to occur at pressure points such as elbow/ chronic licking/ rubbing
What are vesicles and bullae and what are the causes?
- = fluid filled cavities within or beneath the epidermis (blister)
- causes
- frictional trauma
- autoimmune diseases (targeting IC juntions between keratinocytes)
- burns
- viral diseases (FMD)
What is the difference between vesicles and bullae?
- vesicle = <1cm
- bullae = >1cm
What is shown here?
- vesicle and bullae
What is shown by the star?
- sub-epidermal vesicle due to thermal burn
What are examples of vesicular diseases? and how do vesicles form?
- FMD
- vesicular stomatitis
- vesicular exanthema
- swine vesicular disease
What is a pustule and what are the causes?
- vesicle containing pus (=degenerate neutrophils, inflammatory cells)
- causes:
- autoimmune diseases (e.g. pemphigus)
- bacterial infections (e.g. staphylococcal infection = superficial pyoderma)
What is this?
- pustule
- contained within epidermis
What is shown here?
- pustule
- pemphigus foliceus subcorneal pustule
What may erosions and ulcers be the result of? and what do they imply?
- result of:
- mechanical trauma (e.g. pruritus)
- infectious
- inflammation
- neoplasia
- thermal burns
- ischaemia
- chemical damage
- radiation
- Imply
- some degree of necrosis of the ep cells in epidermis
What are these?
- if there is bleeding - damage is underneath the BM (no vessels in the epidermis) = ulcer
Is this more likely to be an ulcer or erosion? Why?
- ulcer
- bleeding
- lesion has crossed BM
What is this showing?
- erosion/ ulceration
- have loss of epidermis and exposure of dermis
What is a crust?
- =consolidated, dessicated, surface exudate that contains keratin, serum, cellular debris (from inflam cells and/ or keratinocytes), variable rbcs (haemorrhage) and often microorganisms
- often the end result is loss of integrity of epidermis
WHat is this?
- crust
- (partially replaces epidermis)
What does this slide show?
- crust
How does crust form?
What is Neoplasia?
- neoplasia in the epidermis can only arise from epithelial cells (keratinocytes)
- benign = papilloma (wart)
- malignant = carcinoma (usually squamous)
Causes of neoplasia?
- often spontaneous
- viral infections (e.g. papillomavirus)
- chronic sunlight exposure (white coated animals)
WHat is this showing?
- papilloma
What is this showing?
- squamous cell carcinoma
- neoplastic cells invade the underlying dermis and form accumulations of keratin
What is this cat presenting with?
- squamous cell carcinoma (SCC)
- ep cells invading tissue underneath
What is atrophy? (dermal response to injury)
- = decrease in the mass of a tissue (skin) due to decreased size/ number of its cells (after its reached its normal size)
- in the dermis = decreased quantity of collagen fibrils; clinically thin, translucent skin, with prominent vasculature
What are the causes of atrophy?
- malnutrition
- endocrinopathies (e.g. hypothyroidism, Cushings)
What is this showing and why?
- atrophy of collagen
- adnexa go into atrophy
What is inflam of the dermis called?
- dermatitis
- inflam cells are present in the dermis (lymphocytes, plasma cells, neutrophils, macrophages, eosinophils)
What are these?
What are the causes of dermatitis?
- infectious (bacteria, viruses, parasites)
- bacteria attract neutrophils and macrophages
- viruses attract lymphocytes and plasma cells
- parasites attracts eosinophils
- autoimmune or immune-mediated
- lymphoplsmacytic inflam
- allergic
- eosinophili inflam
What is erythema?
- reddening of the skin
- due to increased blood supply to the area and vasodilation
- associated with acute inflam
What is eosinophilic dermatitis associated with?
- parasite infection
- allergy-type reaction
- collagen necrosis
- degeneration
What is this condition?
- feline miliary dermatitis
- crusts, ulcers/ erosion/ erythema
What is this animal presenting with?
- cat, flea-allergy dermatitis
- hair loss
- redness
- hyperaemia
- inflam cells in dermis
What is this dog presenting with?
- flea allergy
- erythema and alopecia
What kind of dermatitis is this?
- eosinophilic dermatitis
- flea allergy
- more nuclei
- lots of inflam cells
- oedema in dermis
What is the hallmark of granulomatous/ pyogranulomatous dermatitis?
- mycobacterium spp.
- main inflam cell = macrophage
What inflam is this?
- granulomatous inflam
- lots of macrophages
- few neutrophils
What is this? and what is it caused by?
- feline leprosy
- caused by mycobacteria
What is this?
- Leishmania
What is lymphoplasmacytic inflam caused by?
- chronic infections in general
- diseases characterised by lymphocyte and plasma cells infiltrates:
- viral infections
- autoimmune and immune-mediated diseases
What type of lymphoplasmacytic inflam is this? and what species does it affect?
- discoid erythematosus
- uncommon
- dogs and horses
What type of dermatitis is this showing?
- interface dermititis (obscuring the BM)
What is neutrophilic inflam associated with?
- bacterial infection (either primary or secondary)
- can form discrete abcesses
- common in the dermis associated with:
- rupture of hair follicles
- penetrating injury
What is this?
- subcutaneous abscess
- (dermis, subcutis and pushing on muscle)
What is this?
- neoplasia - benign cutaneous histiocytoma
- seen in young dogs
label this
Where do the main adnexal diseases occur?
- in hair follicle
What is folliculitis/ furunculosis?
- folliculitis- inflam of hair follicle
- furunculosis - inflam of the hair follicle + rupture
What causes folliculitis and furunculosis?
- almost always infectious:
- staphylococcus sp
- demodex sp (mange)
- dermatophytes (ringworm)
Describe the evolution of folliculitis?
