Dermatology Flashcards
stratum basale
location:
function:
what attaches it to the basement membrane?
bottom layer
keratinocyte proliferation & anchors epidermis to dermis
hemidesmosomes
what are desmosomes
intercellular attachments
stratum spinosum
location:
middle, 1-2 layers in haired skin
stratum corneum
location:
function:
what differentiate to form this layer?
outermost layer
forms resistant protective layer/barrier
keratinocytes
melanocyte function
produces melanin pigment that injects into keratinocytes - photoprotection
langerhans cells function
dendritic cells - trap and process antigen (immune surveillance)
functional role of dermis
thermoregulation, physical protection, photoprotective
3 stages of hair follicles
- anagen phase - growth
- catagen phase - transition
- telogen phase - resting (end stage)
components of dermis
acellular - fibers (collagen, elastin, reticulin) + ground substance (h2o, salts, proteoglycans, glycoproteins)
cellular - fibroblasts, macrophages, T cells, mast cells
effect of estrogen & glucocorticoids on sebaceous glands
atrophy and involution
flat discoloration < 1 cm in diameter
macule
macular lesions >1 cm in diameter
patch
solid, elevated, firm circumscribed lesion < 1 cm in diameter
caused by infiltration of inflam cells
associated with hair shaft (folliculitis) or not
papule
elevated, firm lesion with flat top > 1 cm in diameter
plaque
elevated accumulation of purulent material with epidermis
pustule
elevated fluid filled cavity within or below epidermis (< 1 cm diameter)? what if > 1 cm?
vesicle (blister)
bulla vesicle
epithelial lined cavity filled with fluid or semisolid material, located in dermis or subcutis
cyst
raised, solid region of edema, often with irregular borders (e.g. insect bite, type I hypersensitivity)
wheal (hive, urtica)
raised, firm round lesions > 1 cm in diameter
nodule
flat-min raised scale arranged in circular rim (e.g. superficial bacterial pyoderma, fungal infections – ringworm)
epidermal collarette
dilated hair follicle filled with keratin or sebum
comedone
thick, hard hairless plaque often located over pressure points
callus
dried exudate in stratum corneum composed of serum, blood, keratin, degenerate neutrophils
crust (scab)
loose fragments of keratin on skin surface (hyperkeratosis)
scale
partial loss of epidermis
erosion
full thickness loss of epidermis with exposure of dermis (e.g. vasculitis)
ulceration
linear loss of epidermis (e.g. scratch or abrasion)
excoriation
vertical crack in epidermis to the dermis
fissure
rough thickened epidermis, results from chronic scratching/irritation (e.g. non-specific chronic dermatitis)
lichenification
gross lesions of bacterial pyoderma
papules, pustules, epidermal collarettes/epidermitis/folliculitis
histiologic lesions of bacterial pyoderma
perifolliculitis
folliculitis
furunculosis
common causes of bacterial pyoderma in
dogs
horses
pigs
horses & ruminants
S. pseudintermedius (most common)
S. aureus & intermedius
S. hyicus “greasy pig disease”
Dermatophilus congolensis “rain rot”
mechanisms of systemic bacterial infections
bacteremia
bacterial toxins
direct infection of endothelial cells
type III hypersensitivity rxn
lesions of systemic bacterial infections
distribution?
vasculitis (erythematous plaques/macules, dermal edema, hemorrhage bullae, necrosis, well-demarcated ulcerations)
thrombosis
paws, pinnaae, lips, tail
gross lesions of dermatophytosis
patches of alopecia with scaling
papules due to folliculitis/perifolliculitis/furunculosis
histopathologic lesions of dermatophytosis
hyperkeratosis
folliculitis
furunculosis
gross lesions of demodex
how do you diagnose
folliculitis
perifolliculitis
furunculosis
deep skin scrapings, pluck hairs
gross lesions of scabies
pruritis due to hypersensitivity rxn
histologic lesions of scabies
hyperkeratosis
acanthosis
how do you diagnose scabies
superficial skin scrapings
types of infectious microorganisms that cause granulomatous/pyogranulomatous dermatitis/panniculitis (deep bacterial pyoderma)
traumatic implementation of bacteria forms nodules
Feline Leprosy (Mycobacterium lepraemurium)
Botrymycosis - Staph, Strep, Pseudomonas
Nocardia, Actinomyces
types of infectious microorganisms that cause folliculitis (8)
- Staph pseudintermedius
- Staph aureus & intermedius
- Staph hyicus
- Dermatophilus congolensis
- Microsporum canis & gypsum
- Trichophyton verrucosum
- Malassezia pachydermatis
- demodex
primary clinical lesions with allergic dermatoses
distribution?
pruritis - skin lesions from self-trauma – erythema, wheals, alopecia, excoriation, salivary staining, lichenification & hyperpigmentation
face, paws, caudal carpi, distal extremities, ear, ventrum
histologic lesions with allergic dermatoses
eosinophilic & mastocytic perivascular dermatitis with dermal edema
pemphigus complex
mechanism:
histology:
Ab target keratinocytes cell-cell adhesion complexes (desmosomes) which results in acantholysis (the cleavage of desmosomes) that cause pustules & vesicles
acantholytic cells/keratinocytes
Bullous dermatoses occurs at the dermal/epidermal junction and results in vesicles/bullae at points of friction which results in ulcers…what cells are not present
acantholytic cells
discoid lupus erythematous
gross lesions:
histologic lesions:
nasal planum depigmentation, erythema, scaling, loss of “cobblestone” appearance & dorsal muzzle, lips, perioral & ears
interface (dermal/epidermal junction) dermatitis with damage to basal cells
does with SLE test positive for?
anti-nuclear antibodies (ANA)
most common cause of erythema multiforme/toxic epidermis necrolysis
drugs
sebaceous adenitis
clinical lesions:
histologic:
alopecia, scaling (follicular casting), dry/brittle hair
granulomatous/pyogranulomatous inflam, epidermal/follicular hyperkeratosis
different mechanisms associated with alopecia
- follicular dysplasia
- follicular atrophy - genetic, ischemia, trauma, inflam
- abnormal growth/hair cycle arrest - endocrine, nutrition, metabolic
endocrine alopecia
clinical lesions:
histologic lesions:
non-pruritic, bilaterally symmetric, remaining hair coat dull dry & easily epilated, fails to regrow after clipping
hair follicles in catagen or telogen phase with lack of hair shafts
limitations of histologic diagnosis for endocrine alopecia
can suggest endocrine alopecia but clinical testing/clinical signs needed to differentiate disorders
hypothyroidism effect on skin
thyroid hormone needed for anagen stage (growth), so without it, lack of hair growth
hair follicles in telogen without hair shafts
hyperadrenocorticism effect on skin in dogs and cats
calcinosis cutis (dogs)
fragile skin (cats)
mechanisms of depigmentation/hypopigmentation
inherited - piebaldism, albinism, vitiligo
acquired - destruction of epidermal-melanocyte units or reduced melanin synthesis due to tyrosinase or Cu def
mechanism of hyperpigmentation
acquired - chronic inflam or UV exposure = increased proliferation or rate of melanin synthesis
vitamin A & Zn deficiencies
hyperkeratosis
acanthosis
increased proliferation
causes of acquired skin fragility syndrome in cats
defect in collagen production, quality or packaging
- hyperadrenocorticism
- diabetes mellitus
- hepatic disease
lesions associated with short term actinic (solar) injury
sunburn, erythema, erythematous
lesions associated with long term actinic (solar) injury
solar elastosis
actinic keratosis
squamous cell carcinoma
hemangioma/sarcoma
3 type of photosensitization
which is the most common in domestic species?
type 1 primary
type 2 abnormal porphyrin metabolism
type 3 impaired liver function (most common)
types of cancer that cause hypercalcemia of malignancy
AGASACA
T cell lymphoma
multiple myeloma
sporadic carcinomas
due to PTHrP = hypercalcemia
what skin tumors are associated with viral infections?
papillomavirus - squamous papilloma
bovine papillomavirus - equine/feline sarcoids
