pathology of the integumentary systempeople.upei.ca/hanna/skin4/skinl4-webf17.pdf · integumentary...
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![Page 1: Pathology of the Integumentary Systempeople.upei.ca/hanna/skin4/skinL4-WebF17.pdf · Integumentary System Lecture 4 Parasitic / Immune-mediated (web) Paul Hanna Fall 2017 . PARASITIC](https://reader036.vdocuments.net/reader036/viewer/2022062311/60314f2b5f793f04f2783e37/html5/thumbnails/1.jpg)
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Pathology of the
Integumentary System
Lecture 4 Parasitic / Immune-mediated
(web)
Paul Hanna Fall 2017
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PARASITIC SKIN DISEASES
• cause disease directly: inflammation
blood sucking
toxin injection
results: annoyance
reduced production
unthrifty / blemished hides
• cause disease indirectly:
important vectors eg WNV, RMSF, Lyme, Leishmaniasis, dirofilariasis
predispose to pyoderma, myiasis or local viral infections
Diagnosis • history & clinical signs (esp. pruritus) / lesions
• parasite ID
• skin biopsy
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MITES
Demodectic Mange • normal microfauna, neonates acquire from dam
• see mainly in dogs with genetic predisposition &/or immunodeficiency
Localized form
young dogs (3-10 months), usually self-limiting
1 to 5 patchy areas of alopecia + variable erythema, scaling & hyperpigmentation
Generalized form
in juveniles following localized form (~10%)
• in older dogs internal disease &/or immunosuppression
• proliferation of mites folliculitis / furunculosis, 2o pyoderma
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Localized Demodecosis
With localized demodecosis can see focal areas of alopecia,
erythema and/or hyperpigmentation, and comedones.
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Generalized Demodecosis
Generalized demodecosis with secondary pyoderma, note widespread alopecia with scaling / crusting
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Demodecosis
Demodex mites from scrapings
Histopathology showing perifolliculitis with
demodex mites in follicular lumina.
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Sarcoptic Mange (Scabies)
• pigs > dogs > ruminants, horses
• highly contagious, host-adapted varieties (eg. S. scabiei var. suis)
• zoonotic; humans readily parasitized, but usually limited reaction to animal varieties
• lesions due to: mechanical damage from burrowing
irritation from mite saliva and excreta
hypersensitivity to mite products
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Alopecia & excoriations
Marked crusting within ear canal of pig Alopecia, lichenification, hyperpigmentation
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Pruritic papules on human arm (above) which
is a typical skin reaction to animal mites Mite tunneling within cellular crust
Severe excoriations / crusting on a human hand due to
hypersensitivity reaction to an animal variety of mite.
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Notoedric Mange
Cheyletiellosis
Otodectic Mange
Psoroptic Mange
Chorioptic Mange
Psorergatic Mange
Trombiculidiasis Marked crusting and excoriation on face of cat with Notedric mange
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TICKS
• divided into 2 families, ie hard ticks (Ixodidae) and soft ticks (Argasidae)
• vectors for many viral, rickettsial, bacterial & protozoal diseases
• can also cause local skin damage, anemia or paralysis
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• most important cause of skin disease in small animals (C. felis & C. canis)
• can cause pruritus / irritation skin, anemia, infectious disease vectors, HS reactions
• clinically, can see: asymptomatic carriers
flea-bite dermatitis
flea allergy dermatitis
FLEAS
Flea “dirt” (ie flea feces composed of dried digested blood), may be more readily found than the fleas themselves
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LICE (PEDICULOSIS)
Sucking lice - feed on blood and tissue fluids
Biting lice - feed on exfoliated epithelium and debris
Many lice with numerous eggs (nits) attached to hairs.
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FLIES • cause : annoyance (“fly-worry”)
localized skin damage / pruritus (fly bite dermatitis)
+/- hypersensitivity (eg Culicoides HS)
anemia
direct toxicity (eg black fly toxin)
vectors for infectious agents
myiasis
vetgrad.co.uk
Feline Mosquito-bite dermatitis / hypersensitivity.
See characteristic crusted papules on the bridge of
the nose, pinnae and perauricular regions.
Fig 5-92 (Sm An Derm) Fly Bite Dermatitis. Alopecia &
crusting (hemorrhagic) on the ear tip of a dog. Note the
similarity to scabies and autoimmune skin disease.
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Black fly bite on glabrous skin of a dog’s abdomen. Some
animals show this characteristic annular lesion of a central
pale zone of edema, with peripheral erythematous rim.
Don’t confuse this with the human skin lesion associated
with Lyme disease, called erythema migrans, at the site of
the tick bite – because a) skin lesions are often not seen in
dogs at the site of tick bites and b) when rare lesions have
been observed they have been poorly delineated areas of
erythema (rash), urticaria or moist dermatitis
FLIES
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Myiasis - infestation of living animals tissues with fly larvae (maggots / grubs)
Warbles (Hypoderma)
• primarily cattle, occasionally horses & others
• eggs laid on hair larva burrow into skin migrate & overwinter in epidural fat or esophagus
in spring migrate to subQ on back & form nodules mature larvae emerge & pupate on soil
eg damaged hide due to warble fly larvae in subQ nodules along the back of cattle
FLIES
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Myiasis - infestation of living animals tissues with fly larvae (maggots / grubs)
Cuterebriasis
• typically small wild mammals, but occasionally infest cats and others
FIGURE 5-84 (Sm An Derm Atlas) Cuterebra. Erythema and
fibrosis surround the breathing hole of the Cuterebra on the
neck of an adult cat. A purulent exudate is common.
FIGURE 5-85 (Sm An Derm Atlas) Cuterebra. The Cuterebra
has been removed with hemostats. The lesion consists of a
fibrosed tunnel with a purulent exudate.
FLIES
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HELMINTH DISEASE
Cutaneous larval migration
• adults live in non-cutaneous sites while larval stages migrate through skin
Cutaneous Habronemiasis (“summer sores”)
• due to aberrant deposition and migration of Habronemia & Draschia spp larvae
• normally larvae deposited near mouth swallowed develop in stomach
• when larvae deposited on moist skin / wounds by flies ulcerative dermatitis
note: ulcerated / nodular lesions on lip and periocular regions (r/o sarcoid, squamous cell carcinoma)
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Involvement of the prepuce &/or penis is common
On histologic
examination there
is typically
eosinophilic
granulomatous
inflammation,
which often
contain segments
of Habronema
larva within areas
of necrosis.
1.bp.blogspot.com
Ulcerative dermatitis
on fetlock due
Habronemiasis
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Filarial Dermatitis
adults or microfilaria spend some time in the skin
Onchocerciasis
Stephanofilariasis
Dirofilarial (heartworm) dermatitis
Equine cutaneous ochocerciasis. Adults
O. cervicalis live in nuchal ligament and
microfilaria in dermis. The prevalence of
infection is high in North America, but most
horses don’t have lesions. There is strong
evidence that those horses that develop
skin lesions have individual (sporadic)
hypersensitivity to microfilarial antigens.
The characteristic lesions are areas of
alopecia, scaling / crusting and leukoderma.
HELMINTH DISEASE
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PROTOZOAL DISEASES
Leishmaniasis
Sarcocystosis
Besnoitiosis
Fig 6-25 Leishmaniasis. (Atlas Sm An Derm) Alopecia and crusting on the
nose and periocular skin of a Labrador. Note the mild nature of the lesions.
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HYPERSENSITIVITY REACTIONS
IMMUNE-MEDIATED SKIN DISEASE
Definition
response to normally harmless foreign compounds (Ag’s)
most cutaneous HS's are mediated by types I or IV HS reactions
pruritus is a feature common to most HS's
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Diagnosis
• history and clinical signs (esp pruritus) / lesions
• skin biopsy (mostly non-diagnostic)
• intradermal skin testing, elimination of Ag’s, response to therapy
HYPERSENSITIVITY REACTIONS
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1. ATOPIC DERMATITIS
• common in dogs (genetic / familial); less in cats and horses
• complex type I (+/- IV) HS to normally innocuous exogenous Ag's
• epidermal barrier dysfunction transepidermally absorbed allergens (eg dust mites, pollen)
• switching of TH1 to TH2 proinflammatory cytokines + overproduction of specific IgE
mast cell degranulation + inflammatory mediator synthesis pruritus self-trauma
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Gross
• pruritus self-trauma erythema, excoriation, alopecia (esp face / feet / abdomen)
chronicity hyperpigmentation & lichenification
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Histology • early perivascular / interstitial dermatitis
• later hyperplastic perivascular / interstitial dermatitis; often 2o pyoderma / Malasseziasis
Differential Diagnosis • histology non-diagnostic, R/O other allergies and ectoparasitism
Skin biopsy showing edema of
superfical dermis and mild
perivascular / interstitial
infiltrate of inflammatory cells
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2. FLEA ALLERGY DERMATITIS (Flea-bite Hypersensitivity)
most common hypersensitivity of cats and dogs, in flea endemic areas
combination of types I & IV HS to antigens in flea saliva
once sensitized, few fleas are needed for severe reaction
intense pruritus self trauma / secondary infections
Gross
primary lesion is an erythematous papule or wheal
self-trauma alopecia, excoriation & crusts
chronicity hyperpigmentation & lichenification
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Excoriation / crusts / early lichenification
of lateral thorax & lumbosacral area
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Alopecia / excoriations (above) and mostly just
alopecia due to excessive “grooming” (below)
Crusted papules of “miliary dermatitis”
(note millet seeds on bread in top pic)
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Histology
• early perivascular / interstitial dermatitis with eosinophils & mast cells later mononuclear cells
• may see spongiosis &/or eosinophilic microabscesses ("nibbles")
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3. SOME OTHER HYPERSENSITIVITY REACTIONS
Urticaria (hives or wheals) / Angioedema (edematous swellings)
Allergic Contact Dermatitis [Contact HS]
Food Hypersensitivity (Food Allergy)
Equine Insect (Culicoides) Hypersensitivity
Etc.
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SOME OTHER HYPERSENSITIVITY REACTIONS
Allergic Contact Dermatitis [Contact HS]
Allergic contact dermatitis
Occurs following
prolonged contact
(sensitization) with the
offending allergen (eg
plants, cleaners,
synthetic carpets plastic
dishes, rubber chew toys,
etc). Early lesions of
erythema, papules /
plaques and vesicles are
seen in the areas of
contact (esp sparsely
haired regions).
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AUTOIMMUNE REACTIONS
Acantholysis = loss of cohesion between keratinocytes
when autoAb’s or T cells react against self Ag’s
most have hereditary predisposition; rare in domestic animals (dogs > horses, cats)
Pemphigus
• autoAb’s to desmosomal Ag's loss of cohesion (acantholysis) & inflammatory mediators
intraepidermal pustules with acantholytic cells
Fig17-55 (Zachary)
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Immune staining of deposits of intracellular
autoimmune IgG in the upper epidermal region.
Subcorneal pustule with numerous
acantholytic cells admixed with neutrophils
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Pemphigus foliaceus
The primary lesion is superficial pustules, but they are often obscured by hair
coat or have ruptured because they are very superficial and fragile.
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Pemphigus foliaceous
Pemphigus foliaceous, dog. Widespread alopecia, scaling, crusting
Thick crusts on footpads of dog with pemphigus folicaceous.
Crusts result from adherence of the content of ruptured pustules
to the skin surface
Hnilica, Small Animal Dermatology, 3rd ed
Pemphigus often begins on the bridge of the nose, around the
eyes, and on the ear pinnae, before it becomes generalized
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Pemphigus foliaceous
Numerous pustules & epidermal collarettes
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Discoid (cutaneous) lupus erythematosus
• UV light alters keratinocyte Ag’s autoimmune reaction interface dermatitis
Interface dermatitis, with
dense lichenoid band of
lymphocytes & plasma
cells, apoptotic basal
keratinocytes (arrow) &
pigmentary incontinence
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Discoid (cutaneous) lupus erythematosus
Same dog following treatment; note resolution
of inflammation but depigmentation remains. Note, alopecia, erythema, erosion / ulceration,
crusting, & depigmentation of nasal planum region.
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Autoimmune subepidermal blistering diseases (AISBDs)
• a group of diseases with autoAb’s against components of the basement membrane
Bullous pemphigoid collagen XVII (BPAg-2)
Epidermolysis bullosa
acquisita collagen VII
Mucous membrane
pemphigoid
variety: collagen XVII
laminin-5 (332)
BPAg-1
[For information only]
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Grossly see vesicles / bullae which often rupture to leave ulcers
(Hnilica) Bullous Pemphigoid. Severe ulcerative dermatitis on the abdomen
Subepidermal vesicle - complete separation of the entire
epidermis from the dermis at the dermo-epidermal junction.
[For information only]
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Diagnosis
history and clinical signs / lesions
skin biopsy of fresh lesions
immunologic tests – esp IHC
AUTOIMMUNE REACTIONS
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SOME OTHER IMMUNE-MEDIATED DISORDERS
Immune-mediated Vasculitis
Erythema Multiforme
Toxic Epidermal Necrolysis
Vogt-Koyanagi-Harada-like syndrome
Plasma Cell Pododermatitis
Cutaneous Amyloidosis
Infarction of facial skin following
immune-mediated vasculitis
[For information only]
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