Pathology of the Integumentary System Flashcards
What are the top 10 reasons for vet visits?
- atopic or allergic dermatitis
- ear infection
- benign skin neoplasia
- pyoderma
- osteoarthritis
- periodontitis/tooth infection
- upset stomach
- intestinal inflammation/diarrhea
- cystitis/urinary tract disease
- anal gland sacculitis/expression
What is the main function of skin? What does desquamation mean?
protective barrier against fluid loss (hydrophobic), microbiologic agents, chemicals, and physical injury
dead skin cells are continuously shed
How does the skin provide photoprotection?
pigmentations from melanocytes and hair prevent solar damage
What are 6 additional functions skin?
- temperature regulation
- sensory perception (whiskers)
- nutrient storage
- absorptive surface (lotion, topicals)
- immunoregulation
- antimicrobial action
How does the skin aid in vitamin D production? What are the 2 major functions of vitamin D?
- epidermis converts provitamin D3 from UV light into vitamin D3
- vitamin D3 is hydroxylated in the liver into 25-hydroxyvitamin D3
- 25-hydroxyvitamin D3 is converted into the active form of 1,25-vitamin D3 in the kidney
- maintain calcium-phosphorus ratio
- regulate epidermal differentiation and proliferation
What is the skin a major indicator of?
general health and disease
- can see a problem without deep examination
What 5 characteristics are used to describe lesions?
- DISTRIBUTION: anatomic location, focal vs. multifocal, mucous membrane involvement, symmetry
- SIZE
- SHAPE
- CONFIGURATION
- TYPE: primary vs. secondary
Lesion symmetry:
Lesion configuration:
What are primary lesions? What are some examples?
lesion directly associated with the disease process
- macule/patch
- papule/plaque
- pustule
- vesicle/bulla
- wheal
- nodule
- cyst
What are secondary lesions? What are some examples?
modification of a primary lesion that results from evolution of that lesion, traumatic injury, or other external factors
- epidermal collarette
- scar
- excoriation
- erosion/ulcer
- fissure
- lichenification
- callus
What are 6 common examples of lesions that can be primary or secondary? What lesions are the best choice for biopsy?
- alopecia
- scale
- crust
- follicular casts
- comedo
- pigmentary abnormalities
primary lesions
What are 3 common color changes that can happen to skin?
- erythema - reddening
- hyperpigmentation - increase in pigment (dark, black)
- hypopigmentation - decrease in pigment (white)
What are macules/patches? What are 3 examples?
flat, circumscribed lesion of altered skin color < 1cm or > 1cm
- hemorrhage
- lentigo
- vitiligo
Macule/patch:
What are papules? What 2 things are they the result of?
solid elevated lesions < 1cm
- allergic reaction
- bacterial folliculitis
Papules:
What are plaques? What 2 things are they the result of?
flat elevations in skin > 1cm in diameter
- calcinosis cutis
- eosinophilic plaque (allergy)
Plaques:
What are pustules? What 2 things are they the result of?
circumscribed raised superficial accumulations of purulent fluids within the epidermis
- bacterial infection
- pemphigus foliaceous
Pustule:
What are vesicles/bullas? What 4 things are they the result of?
sharply circumscribed elevations of epidermis filled with clear fluid < 1cm or > 1cm
- viral infections
- chemicals
- burns
- autoimmune disease
Vesicle/bulla:
What are wheals? What 3 things are they the result of?
sharply circumscribed raised lesions consisting of edema in the superficial epidermis
- insect bites
- urticaria
- allergic reaction
Wheals:
What are nodules? What 3 things are they the result of?
circumscribed, solid elevations > 1cm that usually exted into deeper layers of skin
- bacterial infections
- fungal infections
- neoplasm
Nodule:
What are cysts? What are 2 common types?
epithelium-lined cavities containing fluid or solid material - smooth, well-circumscribed (see-through nodule)
- follicular cysts
- apocrine gland cysts
Cyst:
What is alopecia? What are 2 common causes?
partial to complete loss of hair
- endocrine dermatopathy
- follicular dysplasia
What is scale? What is a common cause?
sheets of cornified cells that split and separate from underlying epidermis as irregular, thick or thin, dry or oily fragments and may adhere to hair
cornification disorders, like sebaceous adenitis and ichthyosis
What is crust? What is the cause of it?
desquamation composed of dry accumulations of serum, pus, and epithelial or bacterial debris
chronic stages of pustular disease, like bacterial infection or pemphigus foliaceous
What are follicular casts? What is a common cause?
accumulation of keratin and follicular material that adheres to hair shafts extending above the surface of the follicular ostia
sebaceous adenitis
What is comedo? What are 3 examples?
dilated hair follicle filled with cornified cells and sebaceous material (blackheads)
- canine solar dermatosis
- chin acne
- endocrine dermatopathy
What is a common cause of hypopigmentation? Hyperpigmentation?
HYPO: vitiligo
HYPER: postinflammatory, chronic, traumatic, and endocrine skin lesions
What are epidermal collarettes? What 3 things are they a result of?
thin layer of scale that expands peripherally and forms a ring (ruptured pustule leaves a ring of yellow scale)
- superficial bacterial (cocci) infection - pyoderma
- insect bite
- fungal infection
What are scars?
fibrous tissue that replaces normal skin after dermis injury and/or laceration —> often alopecic and depigmented
- healed wound
- surgery
What is excoriation? What are 3 causes?
superficial, linear break of the epidermis
- mechanical trauma
- macerating action of secretions
- constant humidity
Excoriation:
What is erosion? What is it commonly secondary to?
partial thinkness loss of epidermis resulting in shallow, moist, glistening depressions
- vesicle or pustule rupture
- surface trauma
- immune-mediated diseases
What are ulcers? What are 4 common causes?
full thickness loss of epidermis and basement membrane, and at least a portion of the dermis with depression of the exposed surface
ischemic lesions resulting from
1. vasculitis
2. indolent ulcer
3. feline herpesvirus dermatitis
4. feline ulcerative dermatosis syndrome
Fissure vs. erosion vs. ulcer:
What are fissures? What are 3 causes?
deep, linear break from epidermis to dermis
- pemphigus foliaceous
- superficial necrolytic dermatitis
- digital hyperkeratosis
What is lichenification? What is a common cause?
rough, thickened epidermis secondary to persistent rubbing, scratching, or irritation —> increased pigmentation
chronic dermatitis
What is a callus? When/where does it happen most?
thick, firm, hyperkeratotic, hairless plaque with increased skin folds, wrinkles, or fissures
trauma over bony prominences, like elbow, sternum, or side of digits (pressure points)
Describe the lesion distribution and type.
multifocal, variably-sized, ovoid hyperpigmented macules extending from the ventral thorax to the ventral abdomen and both inguinal regions
How does the type of scrapping affect the mites found?
superficial —> Scabies mite (outer layer skin)
deep —> Demodex (deep hair follicles)
What is the best way to achieve cytology for masses?
elevated nodules —> aspiration
What is the best way to begin microbial cultures for superficial infections? Deep infections?
- skin swab for aerobic bacteria
(panniculitis, draining tract, nodules)
- tissue culture (sterile) for aerobic and anaerobic bacteria, Mycobacterium, and fungi
- excisional biopsy
- double punch method
How can dermatophyte cultures be done?
- black light to show infection, direct hair pluck
- run toothbrush over infection
- grown on dermatophyte test medium (DTM) and PCR
How is allergy testing done? When is it performed?
serology or intradermal testing
only preformed when the clinical diagnosis of atopic dermatitis has been made by first ruling out all other causes of pruritus or dermatitis
In what 6 circumstances are skin biopsies performed?
- disease that can only be diagnosed this way
- failure to respond to rational therapy
- severe clinical presentations
- persistent ulcers, vesicles, and bullae
- nodular or neoplastic lesions (cytology not sufficient for grading)
- guide clinical treatment
(PRIMARY (acute) LESIONS ONLY)
What are 3 general rules for what should be biopsied?
- lesions with different spectra
- multiple samples (3-4)
- 6-8mm diameter (4mm for paw, nasal planum, periocular region, eyelid)
What 6 precautions should be taken into account before performing a skin biopsy?
- avoid anti-inflammatory therapy for at least 2 weeks
- treat secondary infections prior
- submit tissue culture for nodular and draining tracts
- don’t scrub the skin or soak in antiseptics
- include crusts and scales in sample
- provide appropriate clinical history and list differential diagnoses
What additional testing can be done after biopsies?
- histochemical stains (Gram, PAS, acid-fast, GMS)
- immunohistochemical stains (infectious agents, neoplasia)
- PCR
- PCR for antigen receptor rearrangements (PARR)
