Lecture 25: Integument 1 Flashcards
List two broad disease groups where pruritus is a significant feature of clinical disease.
- Infectious
- Allergic
True or false. The skin acts as a reservoir for water, electrolytes, fat, carbohydrates, and proteins (mostly within the subcutaneous fat).
T
Name the cell responsible for pigmentation of the epidermis and hair.
Melanocyte
This layer of the epidermis contains blue granules within the keratinocytes. These granules contain a matrix protein that functions as a glue that aggregates and aligns keratin filaments and assist in protection against moisture and microbial agents. What layer of the epidermis is characterized by these features?
Stratum granulosum
What is the antigen processing and presenting cells scattered throughout the epidermis.
Langerhans (dendritic) cells
Steady state of the epidermis is achieved by balance between cell proliferation, differentiation, and desquamation. In what region of the skin is the germinative layer and home to the local stem cells?
Stratum basale
According to your notes, what term best describes the structures that form hair/feathers, produce oils/secretions to protect skin and hair/feathers, as well as produce claws/hooves, horn, etc.
Adnexa
Pruritus (itching) is triggered by histamines, proteolytic enzymes, leukotrienes, prostaglandin and thromboxane A2 and is the reason why infectious and allergic diseases are associated with itching. Some of these important chemical mediators are produced by the resident immune cells in the skin.
Name the key immune cell involved in this process and which of the above listed chemical mediators you associate with this immune cell.
Mast cell and histamine
True or False. Keratinocytes and endothelial cells do not participate in the immune response during inflammation/injury of the skin.
F
True or false. The stratum corneum is the outermost layer and is an important barrier for maintenance of internal environment by preventing loss of water, and also electrolytes, as well as other important molecules.
T
Which of the following regions of the skin are thickest in non-haired skin and areas of high friction?
Basement membrane
Stratum corneum
Stratum spinosum
Stratum basale
Stratum granulosum
Stratum corneum
True or False. The keratin isoforms found in desmosomes and hemidesmosomes are the same and expressed equally in the different layers of the epidermis.
F
True or false. The skin participates in vitamin D production.
T
Compare primary and secondary lesions
primary - spontaneously developing due to disease
secondary - leisons that develop from the primary lesion
Define macule
Is it a 1 or 2 lesion?
less than 1 cm circumscribed area of discolouration
Primary
Define patch
Is it a 1 or 2 lesion?
bigger (>1cm) macule
Primary
Define papule
Is it a 1 or 2 lesion?
<1cm solid evelation
Primary
Define plaque
Is it a 1 or 2 lesion?
large flat extensions of coalescing papules
Primary
Define nodule
Is it a 1 or 2 lesion?
circumscribed >1cm elevation with deep layer involvement
Primary
Define wheal
Is it a 1 or 2 lesion?
sharply circumscribed, raised
will blanch with pressure
from dermal edema
Primary
Define vesicle
Is it a 1 or 2 lesion?
small <1cm blister
Primary
Define bulla
Is it a 1 or 2 lesion?
large >1cm blister
Primary
Define pustule
Is it a 1 or 2 lesion?
small circumscribed pus filled epidermal elevation full of inflammatory cells and acantholytic cells (which are detached and rounded)
may or may not have eosinophils too
Primary
Define cyst
Is it a 1 or 2 lesion?
epithelial lined fluid filled cavity in dermis or SC
Primary
Define abcess
Is it a 1 or 2 lesion?
well demarcated encapsuled fluid/pus filled
Primary
Define epidermal collarette
Is it a 1 or 2 lesion?
rim of keratin that forms after a vesicle or pustule pops
Secondary
Define erosion
Is it a 1 or 2 lesion?
A break in the skin that does not penetrate the basement membrane
it will not scar
Secondary
Define ulcer
Is it a 1 or 2 lesion?
A break in the skin that does penetrate the basement membrane
it will form a scar
Secondary
Define excoriation
Is it a 1 or 2 lesion?
erosion or ulcers due to pruritis
Secondary
Define scar
Is it a 1 or 2 lesion?
fibrous tissue healing
Secondary
Define fissure
Is it a 1 or 2 lesion?
cleavage of thickened skin
Secondary
Define lichenification
Is it a 1 or 2 lesion?
thick hard skin with increased texture
Secondary
Define callus
Is it a 1 or 2 lesion?
thick rough alopecic lichenified plaque
Secondary
Define scale
Is it a 1 or 2 lesion?
accumulation of flaky skin debris
either primary or secondary
1 - seborrhea
2 - chronic inflammation
Define crust
Is it a 1 or 2 lesion?
dry accumulation of material
either primary or secondary
1 - exudate
2 - pyoderma
Define comedo
Is it a 1 or 2 lesion?
pimple
- hair follicle lumen full of keratin
either primary or secondary
1 - cushings
2 - demodex
Define hypotrichosis/atrichia
Is it a 1 or 2 lesion?
reduced hair
either primary or secondary
Define alopecia
Is it a 1 or 2 lesion?
hair loss
either primary or secondary
1 - endocrine disease
2 - pruritus
Define hypertrichosis
Is it a 1 or 2 lesion?
increased hair
either primary or secondary
Define effluvium/defluxion
Is it a 1 or 2 lesion?
increased shedding
either primary or secondary
List 10 potential causes of epidermal inflammation and edema
infectious (bacteria/fungi/virus)
immune
congenital
environ (chemical/physical/radiation)
alopecia/hypotrichosis
nutritional/metabolic
epidermal growth
systemic disease
neoplastic
pigmentation
Who are the main players in inflammation in the skin
keratinocytes facilitate a coordinated response
resident and extravasated immune cells
Define atopy
an individual or familial related hyper-reactivity
related to increased IgE response
can result in the breakdown of skin barriers causing hypersensitivity
Define dermatitis
inflammation of the skin
Compare hydropic/vacuolar degeneration with intracellular degeneration
intracellular = intracellular edema
hydropic = swelling of the basal cells
What lesions are common to skin edema?
vesicle and bulla formation
spongiosis - edema widening the intercellular spaces
Describe the steps of the inflammatory cascade in the skin
- slow blood flow and endothelial adhesions resulting in leukocyte migration
- leukocytes migrate to the perivascular dermis
- exocytosis and migration of the leukocytes
it will form a crust then the neutrophils and fluid reach the surface
in the first 24h = neutrophils. 24-48h = macrophage
Describe the process of eosinophilic inflammation
Type 1 HS
IgE binds mast cells which release inflam mediator
- prostaglandin/leukotriene/cytokine
trigger inflam cascade
- eosinophils/basophils/CD4/macrophage
What is the common cause of eosinophilic skin inflammation
allergy
- atopic dermatitis
- parasites
- anaphylaxis
- urticaria
What are the common clinical signs and lesions you see from pyoderma
erythema and alopecia
epidermal collarettes, pustules and cysts.
in the epidermis and upper follicle
What is the most common agent causing pyoderma
Staphylococcus - either primary or secondary infection
less commonly - pasturella/streptococcus
You are presented with a dog that has pyoderma. Should you administer treatment before taking a biopsy of the skin?
Yes
treat with abx before biopsy to remove any secondary infection pathogens
What species is most affected by exudative epidermatitis? What is the causative agent?
piglets
Staphylococcus hyicus
What species is most affected by mucocutaneous pyoderma? What is the causative agent? What are the common lesions
dogs
erythema/depigmentation/ulcer/crusting/dermatitis in lip fold
Staphylococcus pseudointermedius
What species is most affected by dermatophilosis? What is the causative agent? What are the common lesions
rain scald
common in horse/cow/sheep
crusting/papules on back and distal legs
Dermatophilus congolensis
- gram (+) filamentous bacteria
What species is most affected by scratches/equine pastern dermatitis? What is the causative agent?
horses
Dermatophilus congolensis and Staphylococcus aureus
What is Dermatophytosis? What are the risk factors? What are the common lesions?
a fungal infection that affects keratinized tissue
higher risk if hot and humid
lesions: epidemitis/folliculitis/circular and irregular scale and crusts
What are the common causes of dermatophytosis? What are some concerns with dermatophytosis infection?
microsporun
trichophyton
ring worm
malassezia pachydermatis
candidiasis
it is zoonotic and very contagious
What are the common lesions associated with malassezia pachydermatis infection? How is it acquired?
it is a normal skin microbe but can overgrown
erythema
lichenification
hyperpigmentation
alopecia
Where is candida found/acquired from?
normal skin microflora
rare to cause disease in animals
List 5 types of mites that can cause dermatitis
demodex canis
sarcoptes scabei
notoedre cati
chorioptes bovis
otodectes cynotis
Describe demodex canis infection. What species does it affect
dogs mainly but can cause disease in cat/cow/sm ruminants rarely
affecting either juveniles or the immunosuppressed
generalized: in older animals
localized: in young animals
Describe sarcoptes scabei infection and what species does it infect?
pig and dogs
it is contagious and zoonotic
it lives in the stratum corneum and causes pruritus
What species does notoedres cati infect?
cats
rabbits
What species does chorioptes bovis infect?
cow mange
What species does otodetes cynotis infect
dog and cats in their external ear
What are the common species of fleas that can cause dermatitis? What type of inflammation do they cause? What are the common lesions?
Ctenocephalides canis and felis
they can transmit dipylidium caninum
cause type 1 and 4 HS
result in red papules and secondary excoriations
- in cats it causes miliary dermatitis
What are the types of flies that can cause dermatitis?
biting flies
culcoides midges
causing myiasis (fly bother)
What are 4 causes of epidermal necrosis and ulceration
vasculitis and infarct resulting in geometric necrosis
chemical and thermal burns
ergot/fescue toxicity resulting in vasospasm
feline indolent ulcer
Define necrolysis
separation of tissue due to cell death
What are 5 viral causes of bullous disease? What are the associated diseases they cause
Pox - orf/contagious pustular dermatitis
Herpes - FHV (facial dermatitis/stomatitis)
Calcivirus - feline or vesicular exanthema of swine
Picornavirus - FMD or swine vesicular disease
Vesiculovirus - vesicular stomatitis
List 7 non-viral causes of epidermal bullous disease
pemphigus vulgaris/paraneoplastic pemphigus
lupus erythematosus
chemical or thermal burns
photosensitization
drug reactions - type 4 HS
dermatomyositis
subepidermal bullus dermatoses
What is the pathogenesis of the lesions caused by poxvirus
intracellular edema
ballooning degeneration
macule
papule
vesicle
pustule
hyperplasia and crusting
ischemic necrosis
How do keratinocytes form a tight barrier? What happens if that is damaged?
desmosome proteins hold them together
damage to them result in vesicle/ulcer/pustule
What are 4 different stages of pemphigus disease
When Ig are produced that attack desmosomes in skin
superficial/less severe
1. subcorneal = pemphigus foliaceus
2. panepidermal = pemphigus pemphigoid
3. suprabasal = pemphigus vulgaris
- form uclers in the mouth/mucocutaneous junction
4. subepidermal/subbasal = bullus pemphigoid
- form bullas/vesicles/ulcers
deep/most severe
What is the most common pemphigus disease? Where does it occur most?
pemphigus foliaceus
form superficial vesicles and acantholytic cells on the nose/pinna/periocular skin/footpad/ and coronary band
You are presented with a white faced cow with blisters/exudate and necrosis on its face. What is your top differential
photosensitization
due to reduced pigment on face and exposure to long wave - UVA radiation
What are 4 causes of photosensitization
- ingestion of photodynamic substances like St. johns wars to drugs (phenothiazine)
- abnormal porphyrin metabolism -
- congenital condition in cows - hepatogenous due to liver disease = unable to metabolize chlorophyll/reduced excretion of phylloerythrin
- idiopathic
Why does melanosis and hyperkeratosis occur
response to injury or chronic inflammation
Provide 3 examples of congenital hypopigmentation
reduced melanocutes or production from melaocytes
albinism
piebaldism
vitiligo
What do you suggest to the owner when their animal has hyperpigmentation but no congenital or disease cause
could be nutritional
reduced copper in the diet = reduced tyrosinase which is needed for melanin production
What are the primary causes of secondary hypopigmentation. Why>
due to disease or inflammation
- discoid lupus
- drug reaction
reduced pigment in basal cells due to interface dermatitis
it can change the texture of the nasal planum and skin
Describe hyperkeratosis. Why does it occur? Why is it notable?
thickening of the stratum corneum - orthokeratotic or parakeratotic
scale that can occur secondary to inflammation
it can predispose to bacteria and yeast resulting in pruritus
What is epidermal atrophy? Why might it occur
atrophic dermatosis = reduced epidermal thickness
common due to endocrine disease like cushings
Define epidermal hyperplasia? Why is it significant?
aka acanthosis
formation of a callus = increased stratus spinosum that does not cross the basement membrane
the rete pegs can begin to extend excessively into the skin
- can progress to papilloma which can progress to carcinoma
Define psoriform hyperplasia
long extended rete pegs in an even/uniform manner
Define pseudocarcinomatous hyperplasia
increased irregular hyperplasia but the basement membrane is still intact
aka carcinoma in-situ
What are 4 causes of epidermal plaques
chronic inflammation
allergy/HS
calcinosis cutis
cutaneous lymphoma/preneoplasic disease
List 3 types of non-neoplasic lumps you may find on the skin
hyperplastic lesions
cysts
hamartomas
List 6 neoplasias that arise from the ectoderm
cutaneous papilloma
SCC
sebaceous adenoma/adenocarcinoma
apocrine gland adenoma/adenocarcinoma
perianal gland adenoma
follicular/basal cell tumor aka trichoblastoma
What is the general behaviour of cutaneous papilloma? What does it look like
either squamous or fibrous
most are benign and spontaneously regress
grossly it looks like a exophytic mass with finger-like projections
What are 4 causes of cutaneous papillomas in horses? Compare and contrast
EPV1 = papilloma on lip/muzzle in young (<3yo)
EPV2 = can progress to SCC in old horses
EPV3 or 6 = ear papilloma in all aged horse
BPV 1,2,13 = sarcoids in 1-7yo
- locally aggressive but non metastatic - difficult to remove
- usually in areas of trauma
What species is SCC common in? What causes it? What is its behaviour?
cat/hereford cattle/horse
common in reduced pigmented skin with UVB exposure
locally invasive but not metastatic
- except canine nailbed SCC which is very metastatic
What is one treatment method for perianal gland adenoma?
castration because the tumor is hormone responsive
What species does follicular/basal cell tumors affect most? How does it appear
cat/dog
benign
may or may not have melanin
on head/neck/trunk
List 2 categories of mesodermal neoplasias and the associated neoplastic types of each
round cell tumors
- lymphoma
- mast cell
- cutaneous histiocytoma
- cutaneous and systemic histiocytosis
- extramedullary plasmacytoma
mesenchymal tumors
- lipoma
- fibroma or fibrosarcoma
- hemangiopericytoma
- hemangioma
- hemangiosarcoma
What is a common type of lymphoma affecting the skin?
epitheliotropic T cell lymphoma that may or may not have dermal nodules
What is the common signalment of an animal with a mast cell tumor? What is the common treatment options?
dogs - usually older 9yo
- more aggressive form of tumor
- shar pei/boxers
can occur in cats but it is more benign
teat with antihistamines and wide surgical margins
What is the common signalment for an animal with cutaneous histiocytoma?
young <2yo dogs
what are the tumor characteristics of cutaneous histiocytomas? What are the common associated lesions?
benign macrophage tumors
form button masses that can spontaneously regress on the head and pinnae
What is cutaneous and systemic histiocytosis? What species does it affect?
intersitial dendritic cell tumor with a bad prognosis
bernese mt dogs
What is the characteristics of an extramedullary plasmacytoma?
benign on the ear, lip, or mucocutaneous junction
What is a lipoma? What is its characteristics?
benign SC fat accumulation
What are the features of fibrosarcomas/fibromas? What is a common risk factor?
fibroblast tumors that are locally invasive
associated with vaccines
- esp in cats
What is a hemangiopericytoma? What is its characteristics?
perineurocyte/pericyte origin
aka perivascular wall tumor
low grade malignancy and locally invasive
What are the gross features associated with a hemangioma? What is a common risk factor?
it is a cavernous/flat/well-differentiated tumor
the sun can induce them
- common on the belly of dogs
What is a hemangiosarcoma? What species is it common in? What is its behaviour?
blood vessel endothelium tumor
common in old/adult cats and dogs in unpigmented skin
can recur and metastasize
What are the gross features of a melanocytoma/melanosarcoma?
dark brown to black macules, papules, nodules
What species does melanocytomas/melanosarcomas affect? How does it differ between species?
pigs
dogs:
- <2cm on eyelid/skin = benign
- >2cm on nailbed/mouth = malignant
horse:
- grey/white old >6yo
- on perineum
- usually benign
