derm Flashcards
skin anatomy 3 parts
3 parts:
-epidermis
-dermis
-subcutis (mostly adipose tissue)
epidermis structure 4 layers
-top to bottom
Stratum Corneum
Stratum Granulosum
Stratum Spinosum
Stratum Basale
Stratum Lucidum (nonhaired skin only)
rete pegs/ rete ridges
the basement membrane is the scaffold of wound healing
-hold the epidermis to the subcutis, strengthens connection.
-calluses are thickening of epidermis with more rete pegs.
nerves in the skin
-motor nerves for hair follicle movement and skin contraction
-sensory: itchy, pain. touch, pressure, temperature
hair growth cycle
-humans and poodles anagen is the growing phase
-most mid hair dogs 20% in anagen
-large hair breeds Husky 9% in anagen takes along time for hair to grow back.
-anagen: growing
-catagen: transitional
-telogen: resting
-early anagen
-exogen
follicular growth anagen phase
Anagen = growth stage
Stimulated by:
Thyroid and growth hormone
Melatonin
Suppressed by:
Estrogen and glucocorticoids
-hair Needs protein, starving leads to weak, not growing hair.
functions of hair
-hair follicles: protection, thermal insulation, social communication, sensory perception
-tactile hairs: specialized mechanoreceptors
stratum corneaum function
-insoluable and impermeable, protection
-melanin protects from UV rays
-basement mambrane zone helps with achoring of skin and filering of chemicals
-collagen and elastin: resilience strength support
functions of skin
Adnexal glandular secretions:
Sebaceous = sebum (oil)
Apocrine = sweat to protect skin
surface
Eccrine = foot sweat
Panniculus (subcutis):
Padding and anchoring
Facilitates movement
Store fat, etc.
Claws, hooves:
Thick cornification for traction and
protection
alterations in epidermal growth in response to injury
-hyperkeratosis: increase in thickness of the stratum corneum. normal in some locations (paw pads, nasal planum). parakaratosis are cells with nucli present.
-hyperplasia: increase # of cells in the epidermis, common with inflammation
-Acanthosis: hyperplasia of the stratum spinosum
-hypoplasia: decrease in # of cells/ size (hyperadrenocorticism)
-aplasia: failure to develop (epitheliogenesis importfecta
-apoptosis: cell death, programed kertitination or pathological (Immune disease)
alterations in fluid balance and cell adhesion of the epidermis
-edema: spongiosis is inflammatory change, swelling with some viruses
-acantholysis and vesicles: loss of cohesion between epidermal cells. (pemphigus), pyoderma
-alterations in epidermal growth: atrophy (thin skin in cushing dogs)
inflammatory lesions of the epidermis in response to injury
-exocytosis of leukocytes into the epidermis, vesicles with inflammatory cells and crusts of dried ecaudate on epidermal surface.
epidermal pigmentation in response to epidermal injury
-leukoderma: hyperpigmetation
-lentigo (common) older orange cats, where they rub skin (anus, face, ears) dark pigments, normal.
response to injury dermis
- Alterations in dermal growth or differentiation
- Atrophy
- Fibrosis
- Solar elastosis
-horses get exuberant granulation tissue - Inflammatory lesions and depositions, fragmented collagen
follicular atrophy in response to injury
PHYSIOLOGIC ATROPHY
Growth of hair is seasonal* and it
is controlled by environmental*
and genetic factors
PATHOLOGIC ATROPHY
Hormonal abnormality*
Inadequacy of vascular supply
Inflammation*
Systemic illness & Stress
panniculitis
-inflammation of SUBQ fat
causes:
primary: vit E deficiency, vaccination
secondary: bacterial foliculitis
folliculitis
-inflammation of the hairfollicle
-causes: parasites (demodex), bacteria (staph), dermatophytes
-furnucolosis: perforating folliculitis, has edema, hair follicle fully ruptures and invades tissue around it
-the progression of folliculitis is: perivascular, mural, luminal , rupture, drain
congenital or hereditary skin disorders
epitheliogenesis imperfecta:
1 complete failure of epithelium and adenxa to develop
2 small lesions animal will be fine
-bacteria can get in and lead to septicemia (e.coli)
ichthyosis fetalis:
1 FATAL, congenital and inherited disorder (calves, puppies)
-usually on feet and muzzle, on charlae cattle entire body. not common.
Temperature injuries cold
frostbite:
Freezing of water in and around cells -> ice crystals pull water from cells -> increased osmotic pressure
-leads to vasoconstriction-> tissue anoxia
-endothelial damage-> decreased BP
-coagulation necrosis from blood clots
temperature injuries heat
burns
Dry heat (hair dryer) -> desiccation + carbonization
Moist heat (hot water) >coagulation of tissue
different degrees of burns
Partial thickness = 1 st (epidermis) and 2nd degree burns:
Accelerated cellular metabolism
Inactivation of enzymes
Vascular injury
Scarring, but adnexa are preserved, regeneration
Full thickness = 3rd degree burns
Coagulation of the epidermis and dermis
4 th degree burns extend into the fascia and SQ
Sloughing
temperature solar injury
-called Actinic dermatosis
UVB is most damaging
Acute = sunburn
Chronic = solar dermatosis or neoplasia
-lesions develop in poorly haired or lighty pigmented sites (exp abdomen)
photosensitization
Pathogenesis:
UV light absorbed by photodynamic chemical in skin tissue -> reactive oxygen
(free radicals) -> mast cell degranulation
-erythema and edema–>blisters, excudation, necrosis, sloughing
photosensitization types
Primary photosensitization
type 1
Ingestion of preformed photodynamic substances
Administration of drugs (tetracycline, sulfonamides…)
type 2
Abnormal porphyrin metabolism
(NB: Triple “I”: ingestion, injection and inheritance)
Secondary photosensitization
-type III Hepatic diseases
plants and substances associated with photosensitazation
Plants associated with hepatic photosensitization:
Lantana
Puncture vine
Mycotoxins
Plants with photodynamic substances:
St. John’s wort
Buckwheat
Spring parsley
chemical injruy
Contact Irritant Dermatitis
Direct damage caused by caustic
chemicals
Systemically distributed
chemicals:
Arsenic, mercury, thallium, iodine, Plants: selenium, mimosine,
trichothecenes
lesions: Hyperkeratosis, squamous
metaplasia
ergot poisoning
Pathogenesis:
Ingestion of grain/seeds infected by Claviceps purpurea -> produce ergotamin ->
arteriolar spasm and endothelial damage -> ischemia of distal extremities, tail etc.
Appetite, cardiovascular function, endocrine activity, gastrointestinal motility, muscle
contraction, and temperature regulation (vasoconstriction)**
-gangrene feet or fescue foot
fescue foot
Tall fescue is infected with the fungal endophyte Neotyphodium
coenophialum
The endophyte produces Ergot Alkaloids
injection site reactions
Injection site reactions (rabies vax alopecia) 3-6 months after vaccination** then hair growns back
-ischemia and damage to hair follices, panniculitis
-usually self harm diseases from atopy or allergic reactions
acral lick dermatitis
Hyperkeratosis, acanthosis,
lick granulation tissue and fibrosis
-common, usually has underying cause, food allergies or skin damage.
-lesions: circumscribed, hairless, erythamtous, ulcerated.
hot spots (pyotraumatic dermatitis)
-moist crusty lesion
-common in dogs
Occur secondary to licking and scratching
Usu. Underlying diseases
-self inflicted trauma, biting, pain
gross: excudative, ulcerative, red egdes, alopecia.
infectious skin diseases defense mechanisms
Cutaneous infections develop when there is disruption of dermal
defense mechanisms
Physical barrier (hair coat, pigment, desquamation of stratum corneum)
Chemical and biochemical barrier (lipids, transferrin, antimicrobial substances)
Biologic barrier (microbial flora)
Innate immunity (transferrin, antimicrobial substances, defensins)
Acquired immunity (antibodies, lymphocytes)
contagios ecthyma ORF
Parapoxvirus
young sheep and goats
High morbidity and low mortality
Lesions: proliferative, crusting dermatitis
Mouth -> oral mucosa, eyelids, and feet
$$ weight loss in lambs
Zoonosis possible (milkers nodules)
papilomaviruses
GAIN access through defects in epithelium
ENTER basal layer
3 outcomes:
1. Virus DNA replicates with cells.
2. Virus converts from latent to productive
3. Virus is integrated into the genome -> tumor
Exophytic or endophytic papillary benign masses
Sarcoids = fibropapillomas (particularly in equids)
Bovine papillomavirus 1 and 2 infection of fibroblasts
Frequently recur, may regress, locally aggressive (non-metastatic)
exudative epidermitits
-greasy pig disease
-caused by staphlococcus hysius
-neutrophillic pustules that develop into crusts in pigs and dogs
-acute often FATAL dermatitis of neonatal piglets, mild in older piglets
deep pyoderma
-deep bacterial infections involve the entire infundibular, isthmic and/or inferior portion of the hair follicles +/- surrounding dermis and subcutis.
Less common than superficial pyoderma
causes:
S. pseudointermedius folliculitis/furunculosis in dogs
Cat fight abscesses
Often secondary
feline leprosy
-caused by Mycobacterium lepraemurium
Cold, wet areas – PACIFIC NORTHWEST (USA/CA) BC and washington
PCR test only
Gross: Head, neck and limbs – SQ nodules and crusts
Histo: two patterns
1. diffuse granulomatous w/o necrosis, many intrahistiocytic acid fast bacilli
2. granulomas with central necrosis, surrounded by lymphocytes, few
acid fast bacilli
Erysepelas
Secondary to systemic bacterial infections, usually in finisher pigs 12 weeks of age.
Erysipelothrix rhusiopathiae (“diamond skin disease”) due to rhomboid shaped skin lesions
Vasculitis, thrombosis and ischemia (infarction) central of single BV
morph: dermal and epidermal infarctions
contagious foot rot
Pathogenesis:
Trauma & moisture + Bacteroides nodosus and Fusobacterium necrophorum
B. nodosus produces potent proteolytic enzymes
F. necrophorum is predominantly
responsible for necrosis resulting in
separation and sloughing of hooves
dermatophilosis (rain rot)
-associated with prolonged wet skin, keep dry for treatment.
-ZOONOTIC on fingers
-horses and cattle, usually young.
sheep= lumpy wool
-lesions: crusts with matted hair over back and distal extremitires. paint brush on pulled hair
mycotic skin disease ringworm
-RINGWORM: caused by mycrosporum canis/ trichophyton.
Love the Stratum Corneum layer and
Hair Shafts
DO NOT have to enter the living skin tissue to cause disease
ZOONOTIC
Asymptomatic cats – Toothbrush technique
mycotic skin infection yeasts
-malassia pachydermatis
-lipophilic yeast normal in ear canal and skin
lesions: hyperpigmented, alopecic, scaly
Microclimate or host defenses changed
Mostly interdigital, otic, perianal, and intertriginous (spots that rub)
ectoparasites mites
-demodex canis: demodectosis.
in juvenile dogs from the dam. they have underlying disease causing immune suppression.
-localized ( face or forlegs )or generalized scaling. not pruritic unless pyoderma.
-deep skin scraping
-sarcoptic mange (zoonosis) dogs and cats. extreme puritis
-cheyketiella (walking mange) looks like dandruff on fur
-chortoptic mange (cattle)
lice skin diseases
-pediculosis
-from biting or sucking lice, whole cycle on host
ectoparasites causing skin lesions myisasis
-larval infestation by dipterous flies
-blow flies and fresh flies
-eggs on wounds-> larve secrete enzymes-> holes and ulcerated skin.
-cuterebra sp. (kittens)
-screwworm in cattle $$
screwworms
New world = Cochliomyia hominivorax
Old world = Chrysomyia bezziana
Tropical climates
Screwworm flies deposit eggs in
wounds or near mucocutaneous
junctions -> develop into L1 and feed on
tissue -> soon develop into L2
-regulatory pest
cutaneous habronemiases
Habronema or Draschia sp. larvae
Skin that is traumatized or moist.
Medial canthus of eye or prepuce.
Unable to penetrate normal skin
-horse disease on mouth or penis
immunological diseases rxn types
- Hypersensitivity: reaction to normally harmless foreign substances.
– Most are type I and IV reactions in skin
– Common in dogs and horses
– Less common in cats, uncommon in FA - Autoimmune: antibodies or T lymphocytes react against self-antigens.
– Tend to be type II and III.**
– Cutaneously manifested autoimmune diseases are uncommon in domestic
animals.
Urticatia and Angioedema
- Urticaria = hives: edema of the
superficial dermis - Angioedema: edema of the deep
dermis and subcutis - Most common in dogs and horses
- Causes:
– Immunologic: foods, drugs, antisera,
insects
– Non-immunologic: heat, stress, exercise
atopic dermatitis
-Genetically predisposed** inflammatory and pruritic allergic skin disease
* Type I hypersensitivity**
* Average age of onset is from 1 to 3 years
Skin is the major target organ in dogs, cats, and horses
Route of allergen exposure could be respiratory or skin
It is suspected to be predominantly percutaneous absorption of allergens
-2nd most hypersens in dogs
-lesions: rubbing, PURITIS, alopecia. do allergen test
flea bite hypersensitivity
Mixed type I and type IV: Cutaneous basophil hypersensitivity
* Dogs and cats
* Pruritic papular dermatitis -> self-inflicted trauma and chronic lichenification (thickening of skin)
* Fibropruritic nodules: core of collagen covered by a hyperplastic
epidermis
mosquito bite hypersensitivity
- Type I hypersensitivity
– Intradermal skin tests
– Prausnitz-Kustner tests - Primarily on the external nose -> nasal planum, periocular skin, pinnae and less commonly foot pads.
- Erythematous papules ->crusts, ulcers, alopecia
- Hypopigmentation or hyperpigmentation
food allergies
-common and misdiagnosed
Frequent skin and ear infections.
May also present with vomiting and diarrhea.
Similar presentation to Atopy, at any age
Need to do a strict elimination trial to determine the foods animals are
allergic to diagnose
(ELISA assay is not reliable predictor of these).
contact dermatitis
Type IV reaction:**
– Haptens and cytotoxic T cells
– Eosinophils are variable
* Chemicals: aniline dyes in carpets, plant resins, chemicals in shampoos, plastic food dishes.**
* Pruritus with self-inflicted trauma
* Regions in contact with antigen.
* Spongiotic superficial perivascular
dermatitis, epidermal hyperplasia
with varying numbers of eosinophils
pemphigus and 2 types
Gross: Transient vesicles or bullae
Histo: Acanthosis
Type II reaction**
Autoantibodies against proteins responsible for cell adhesion
(desmosomes)
Damage to desmosomes ->acantholysis ->formation of bullae
pemphigus folaceous: when vesicles become pustules –> secondary crusts and scales
-dogs and cats: NOSE then ears, eyes, neck
* Horse: subcorneal pustules
* Dog: stratum spinosum
pemphigus vulgaris: Basal cells attached to basement
membrane -> tombstoning
Mucocutaneous junctions
More severe than PF
-rare, oral skin.
systemic lupus erythematosus
Type III response**
Defective T cell suppressor and cytokine disregulation
Immune complexes formed and deposited in skin
Basal cell or keratinocyte degeneration
-dogs, cats, horses: uncommon. look for in the nose. lichenoid inflammation
hyperthyroidism clinical on skin
-cats
-self inflicted alopecia (forearms and bellys)
-rough appearance, thin
hypothyroidism on skin
The most common endocrine dermatosis in dogs
Age: over 6 years
Intolerance to cold
Obesity
Hair coat dry, dull, coarse, sparse
Alopecia
Adnexal atrophy
Dermal edema
Hyperpigmentation
Scaling
hyperadrenocorticism on skin
Cortisol excess:
Adnexal atrophy ->alopecia
Fibroblasts inhibited -> thin skin
Hepatic glycogen -> hepatomegaly
Collagen/elastin change -> dystrophic calcification (calcinosis cutis)
Immunosuppression -> infections
Causes:
Pituitary (85-90% of dogs)
Adrenocortical (10-15% of dogs)
Iatrogenic
The second most common endocrine dermatosis in dogs
hyperestronism on skin
Males and females
Sertoli cell tumor (cryptorchid)
Ovarian cysts
Atrophied hair follicles
-swollen vulva in females gross looks like hypothyroid skin
alopecia X
Dogs with normally PLUSH hair coats, 1-2 years old
The head and distal extremities are often spared of alopecia
Normal thyroid and glucocorticoid levels
Skin biopsy samples with telogen follicles
(retained hair shafts and flame follicles)
-permanent disease, neutering may work. some dogs respond to melatonin
seborrhi disease complex
-chronic disease complex secondary to abnormalities of the sebasceous glands associated with a change from bacteria to pathogenic.
Seborrhea Sicca - Dry form
Dry skin and white-gray scales.
Seborrhea Oleosa - Greasy form
Scaling and excessive brown to yellow lipids that adhere to the skin and hair.
-primary ideopathic is most common
-secondary with inflammation
ichthyosis
Cattle and dogs
Scaly, cracked skin
-ichytosis fetalis - FATAL, congenital fetal disorder,
zinc responsive dermatosis
Dogs (pigs)
Lesions: scaling and crusting with marked diffuse parakeratosis** eyes and nose
Pathogenesis:
Inherited reduced ability to absorb Zn from the intestine (Alaskan
Malamute and Siberian husky)
Large breed, rapidly growing pups – low zinc diets. they need zinc supplaments
esonophilic skin diseases
Eosinophilic plaques:
Common in cats
Possible link to hypersensitivity reactions
Eosinophilic granulomas:
Horses, dogs and cats
Flame figures, eosinophil degranulation
Lesions: nodular dermatitis, indolent ulcers
juvinille sterile granulatamous disease
Puppy strangles
No microorganism identified (sterile lesions)
Secondary bacterial infections
Lesions: pustular and nodular dermatitis with edema (facial mostly)
tumors of the skin
-squamous cell carcinoma (cats* nose)
-histocytoma (common), regress on their own
-lipoma (cut open, hide Mast cell tumor. boxers**)
-injection site fibrosarcoma (FLV, rabies)
-basal cell tumors
-sebaceous gland hyperplasia
