Skin & Immune Mediated Disease 1 Flashcards
what are the skin defences
- hair –> thermal insulation & thermal dissipation
- melanocytes –> photoprotection
- epidermal barrier –> skin surface lipids & stratum corneum
- innate immunity
- adaptive immunity
what are the layers of skin
cornified cell envelope
stratum corneum - comeocyte
granular layer - lamellar granules
spinous layer
basal layer
how is the physical and permeability barrier of skin regenereated
by process of keratinization –> proliferation + differentiation + cell death
what is needed for optimal barrier function
- lipid bilayer
- cornified envelope structure
- filaggrin
- corneodesmosomes
- control of desquamation
what is the cornified envelope structure
loricrin, involucrin, filaggrin
what is filaggrin
formed from profilaggrin (keratohyalin granules)
binds keratin filaments together
breaks down to amino acids (natural moituring factor)
whwat is corneodesmosomes
provides structural integrity
what is control of desquamation
balance of stratum corneum protease inhibitors & proteases
skin pH
what are the portals of entry into the skin
epidermis –> absorption (lipophilic drugs), direct contact (caustic chemicals), colonization (dermatophytes), penetration (hookworm larvae), impaired barrier (micro-organisms, allergens)
what is adnexa
entry via follicle ostium
rupture of follicle or adnexal glands
what is entry via dermis and panniculus
blood vessels
nerves (rare)
what is entry via underlying tissues
penetration by damaged bone
extension from adjacent tissues
what are the patterns of skin disease
- epidemiology (breed, sex, location, season)
- clinical presentation (lesions, distribution, configuration)
- histopathology (pattern analysis)
what are examples of epidemiology patterns
- breed (skin fold dermatitis)
- sex (symmetrical alopecia)
- location (cutaneous hemangiosarcoma)
- season (flea allergy dermatitis, more common in temperate climates, seasonal in colder)
what are the clinical patterns of skin disease
macroscopic pathology
lesion distribution
lesion discription (size, shape, colour, consistency)
lesion type (inflammatory, hyperplastic, alopecic/hypotrichotic (bald), tumoral/neoplastic (nodular))
what is sarcoptic mange
what is demodectic mange
what are primary skin lesions
develop spontaneously as a result of underlying disease
useful in trying to determine aetiology and pathogenesis of disease
what is secondary skin lesions
evolve from primary lesions or induced by self-trauma or external factors
complicate the picture and make diagnoses difficult
what is macule, papule, vesicle, pustule, wheal, cyst, nodule
primary skin lesions
- macule or (>1cm) patch
- papule or (>1cm) plaque
- vesicle or (>1cm) bulla
- pustule (or abscess)
- wheal (or hive)
- cyst
- nodule (1-2cm); tumour (>2cm)
what skin lesion is this
macule
a circumscribed, non-palpable spot characterized by a change in the colour of the skin
a larger lesion > 1.0 cm is a patch
what skin lesion is this
macule
what skin lesion is this
maculopapular rash
a small solid elavation of the skin <1.0cm diameter
what skin lesion is this
papule
what skin lesion is this
vesicle or bulla
sharply cicrumscribed epidermal elevation filled with clear fluid
may be intraepidermal or subepidermal
a bulla is similar but >1.0cm diameter
what skin lesion is this
vesicle or bulla
what skin lesion is this
pustule
may be intraepidermal, subepidermal or follicular
typically contain neutrophils and bacteria but may contain eosinophils (eosinophilic pustule) and/or be sterile
what skin lesion is this
pustule
what skin lesion is this
wheal (hive)
a circumscribed lesion due to edema, often transient
what skin lesion is this
wheal (hive)
what skin lesion is this
cyst
an epithelium-lined cavity containing fluid or solid (inspissated) material
smooth, well circumscribed, usually fluctuant
what skin lesion is this
cyst
what skin lesion is this
nodule
a circumscribed solid elevation that is >1.0cm diameter
usually due to massive cell infiltration that may be inflammatory or neoplastic
what skin lesion is this
nodule
what skin lesion is this
plaque
a large (>1.0cm) flat-topped elevation formed by extension or coalescence of papules
what skin lesion is this
plaque
what skin lesion is this
tumour
a mass of >2.0cms that may be neoplastic or non-neoplastic (ex. granulomatous)
but term often used to imply neoplasm
what skin lesion is this
abscess
a localized collection of pus in an area of tissue destruction surrounded by inflammation
usually more deeply located than a pustule
what skin lesion is this
abscess
what are the differentials for a lump in the skin
abscess
granuloma
cyst
neoplasm
hematoma
what are secondary skin lesion examples
- epidermal collarette
- exocriation
- erosion or ulcer
- fissure
- scar
- lichenification
- callus
what skin lesion is this
collarette
a circular rim of scale (loose or peeling keratin) that evolves from a pustule vesicle or bulla
what skin lesion is this
collarette
what skin lesion is this
excoriation
erosions or ulcers caused by self trauma (scratching, rubbing, biting)
typically linear they generally indicate pruritus
what skin lesion is this
excoriation
what skin lesion is this
erosion
loss of part of the epidermis, depressed, moist, glistening
what skin lesion is this
erosion
what skin lesion is this
fissure
linear crack or break from the epidermis to the dermis
what skin lesion is this
fissure
what skin lesion is this
lichenification
thickening of the skin with increased creases
what skin lesion is this
lichenification
what skin lesion is this
crust
dead keratinocytes plus neutrophils +/- bacteria
what skin lesion is this
crust
what skin lesion is this
cutaneous callus
localized areas of skin thickening/lichenification
develop over pressure points –> elbow, hocks, sternum (smaller breeds ex. dachshund)
what are the causes of skin disease
vitamin d
v: vascular
i: infectious/inflammatory/immune-mediated
t: trauma
a: autoimmune
m: metabolic/toxic
i: intervention/iatrogenic, idiopathic
n: neoplastic
d: degenerative
what are important factors in skin disease
often several overlapping processes may occur together (generalized demodex)
most conditions provoke an inflammatory reaction
skin is limited in how it can respond
