Jubb and Kennedy Flashcards
What are beta-defensins and cathelicidins?
Antimicrobial peptides
What effect does vitamin D3 have on keratinocytes?
It regulates epidermal differentiation and proliferation
Match the keratins with the layer of epidermis they are found:
K5 and K14
K2
K1 and K10
Basal layer keratinocytes
Suprabasal keratinocytes
Stratum granulosum
K5 and K14 - basal layer keratinocytes
K2 - stratum granulosum
K1 and K10 - suprabasal keratinocytes
Desmocollins and desmogleins (cadherin proteins) make up which epidermal structure?
Desmosomes
Which epidermal structure contains glucosylceramides, sphingomyelin, glycerophospholipids and cholesterol sulfate (plus modifying enzymes)?
Lamellar bodies
Which enzyme catalyses the formation of the cornified envelope by cross-linking small proteins (e.g. involucrin, loricrin and cystatin A)?
Transglutaminase 1
In the pig, cat, cow, sheep, goat, horse and human, Birbeck granules are found in which cells?
Langerhans cells
Which epidermal cells express CD1, MHC II, CD45, vimentin and S-100?
Langerhans cells
BP230 (BPAg 1) and plectin form which part of the hemidesmosome?
Cytoplasmic plaque
alpha6 beta4 intergrin and BPAG2 (type XVII collagen) make up which part of the hemidesmosome?
Transmembrane portion
alpha6 beta4 intergrin binds to laminin 5 - where is laminin 5 located?
It is a component of the anchoring filaments of the lamina lucida
_____________ are composed of type VII collagen and form looping arrays with one or both ends attached to the lamina densa, thereby anchoring the BMZ to the dermis.
Anchoring fibrils
Which cytokines can stimulate mast cell proliferation and differentiation?
Stem cell factor (SCF) and T cell - derived cytokines: IL-3 IL-4 IL-9 IL-10
Which areas of skin are devoid of sebaceous glands?
Footpads and nasal planum
Ballooning degeneration of the epidermis is the result of intracellular oedema and is characteristic of which disease process?
Viral infections, particularly herpesvirus and poxvirus
What is the term used for dermal deposition of amorphous eosinophilic material on collagen fibres with an infiltrate of eosinophils?
Collagen flame figures
Dystrophic mineralisation of the hair follicle basement membrane can be seen as a senile change; which breed is particularly affected?
Poodles
_________ are dermal papillae devoid of attached epidermal cells that project into a vesicle or bulla.
Festoons
What are the four types of epidermal hyperplasia?
Regular (or psoriasiform)
Irregular
Papillated (digitate projections ABOVE the skin surface)
Pseudocarcinomatous (extreme irregular hyperplasia that may demonstrate increased mitotic activity and branched/fused rete pegs)
What are the differentials for eosinophilic perivascular dermatitis?
Ectoparasites Food allergy Atopy Zinc-responsive dermatosis Equine multisystemic eosinophilic epitheliotropic disease Chronic pyoderma
List a differential for:
Pure perivascular dermatitis
Perivascular dermatitis with spongiosis
Pure perivascular dermatitis - acute hypersensitivity reactions and urticaria
Perivascular dermatitis with spongiosis - hypersensitivity reactions, acute contact or irritant dermatitis, ectoparasitism, feline eosinophilic plaque, feline miliary dermatitis, and viral infections.
List a differential for:
Perivascular dermatitis with epidermal hyperplasia
Perivascular dermatitis with hyperkeratosis
Perivascular dermatitis with epidermal hyperplasia - This is a common, non-diagnostic, chronic reaction pattern e.g. chronic hypersensitivity reactions, acral lick dermatitis, and any dermatitis that has undergone chronic irritation and trauma.
Perivascular dermatitis with hyperkeratosis - The presence of parakeratosis suggests zinc- responsive dermatosis, chronic ectoparasite hypersensitivity, or Malassezia dermatitis.
Name two diseases that show a cell-poor interface dermatitis on histopathology
Dermatomyositis Ischemic dermatopathy Erythema multiforme Drug eruptions Graft-versus-host reactions Bovine viral diarrhoea Bovine pseudolumpy skin disease
Which type of hypersensitivity reaction leads to vasculitis?
Type III
Name two differential diagnoses for neutrophilic vasculitis
Hypersensitivity reactions Septicemia Connective tissue disorders Equine purpura hemorrhagica Rocky Mountain spotted fever Classical swine fever Thrombophlebitis Idiopathic disorder
Name two differential diagnoses for lymphocytic vasculitis
Dermatomyositis
Malignant catarrhal fever
Vaccine-induced panniculitis
Rarely in cutaneous lymphoma
Name two differential diagnoses for eosinophilic vasculitis
Arthropod insult Drug eruptions Food hypersensitivity Equine axillary nodular necrosis Idiopathic nodular eosinophilic vasculitis in horses Feline eosinophilic granulomas Rarely in mast cell tumours
Tuberculoid granulomas can be seen in tuberculosis, feline leprosy, atypical mycobacterial infection and which other infection?
Corynebacterium pseudotuberculosis
Which MNGC have nuclei that form a circle or semicircle at the periphery of the cell?
Langhans cell
Which MNGC have nuclei that form a wreath that surrounds a central, homogeneous, amphophilic core of cytoplasm that is, in turn, surrounded by abundant foamy cytoplasm
Touton cell
Which MNGC have nuclei that are scattered throughout the cytoplasm
Foreign body
What are Russell bodies?
Eosinophilic intracytoplasmic inclusions in plasma cells; accumulations of glycoprotein are largely globulin and may be large enough to displace the cell nucleus.
Name a disease where you see: Subcorneal pustules/vesicles Pustules/vesicles in stratum spinosum Suprabasilar pustules/vesicles Intrabasilar vesicles
Subcorneal pustules/vesicles - PF, superficial pyoderma, hypersensitivities (eos)
Pustules/vesicles in stratum spinosum - pemphigus complex, viral disease, rarely in SND/NME
Suprabasilar pustules/vesicles - pemphigus vulgaris
Intrabasilar vesicles - lupus, dermatomyositis, EM, GvH disease TEN
In which species is follicular inflammation most common?
Dogs
Idiopathic sterile eosinophilic folliculitides may be seen in which species?
Dogs and cattle
Name two causes of sterile eosinophilic folliculitis in cats and horses
Hypersensitivity reactions (mosquito-bite hypersensitivity, atopy, food allergy, onchocerciasis, equine eosinophilic granuloma, Culicoides hypersensitivity, flea-bite hypersensitivity). Feline herpesviral dermatitis.
What type of folliculitis is seen in pseudopelade?
Mural folliculitis
Panniculitis can be associated with which vitamin deficiency?
Vitamin E deficiency
Which veterinary species has harlequin ichthyosis been reported in?
Cows
Kudu (antelope)
In epidermolytic ichthyosis, what are the histopathological findings?
Vacuoles and lysis of keratinocytes within the spinous and granular cell layers, which occur along with hypergranulosis and hyperkeratosis.
Epidermolytic ichthyosis (a defect in keratin formation) is seen in which breed of dog and genetic mutation?
Norfolk terrier
KRT10 mutation
Which gene mutation is associated with nonepidermolytic ichthyosis in JRTs?
Transglutaminase 1 (TGM1)
Match the following breeds with the gene mutation associated with nonepidermolytic ichthyosis:
Golden retrievers
American Bulldogs
PNPLA1
ICHTHYN/NIPAL4
Golden retrievers - PNPLA1
American Bulldogs - NIPAL4/ICHTHYN
CKCS nonepidermolytic ichthyosis is associated with which clinical signs?
Keratoconjunctivitis noted from the beginning of eyelid opening A roughened/curly haircoat Scaling with abdominal hyperpigmentation Footpad hyperkeratosis Nail dystrophy
Hereditary zinc deficiency has been reported in which veterinary species?
Cattle
Bull terrier dogs
At what age are skin lesions apparent in lethal acrodermatitis in Bull terriers?
6-8 weeks
Which organ is small or absent in hereditary zinc deficiency in cattle and Bull terriers?
Thymus
Which type of EB is this?
Cytolysis of basal keratinocytes produces intraepidermal clefting. This form of the disease is caused by fragility of the epidermal basal cells because of mutations in basal cell–specific keratins 5 and 14.
Epidermolysis bullosa simplex
Which type of EB is this?
Clefting occurs within the lamina lucida because of abnormalities of the anchoring filament-hemidesmosome complexes, which may be reduced in number and poorly formed or may be completely absent.
Junctional epidermolysis bullosa
Most cases of JEB are the result of a deficiency or abnormality in one of the hemidesmosome-associated proteins laminin-5, collagen XVII (also called BPAG 2 and BP180), or integrin α6β4, or the extracellular protein LAD-1.
Which type of EB is this?
Characterized by a split in the superficial dermis below the lamina densa in the region of the anchoring fibrils, which are fewer in number and distorted or completely absent. The molecular cause is a mutation in the anchoring fibril protein, type VII collagen.
Dystrophic epidermolysis bullosa
Which special stain can help locate the basement membrane zone in histopathology of EB?
PAS
EBS has been associated with which gene mutation in cattle?
KRT5
JEB in German black-headed mutton sheep has been associated with which mutation?
LAMC2 (reduced laminin-5)
Which gene mutation has been associated with JEB in Breton and Comtois horses?
And American Saddlebreds?
Breton and Comtois - LAMC2
American Saddlebreds - LAMA3
Which gene mutation is associated with JEB in GSHP?
The disease is associated with reduced expression of laminin 5 and is caused by a mutation in the LAMA3 gene for the laminin α3 chain.
What are ‘corps rounds’?
Dyskeratotic keratinocytes with small pyknotic nuclei, a perinuclear clear halo, and eosinophilic cytoplasm
Autosomal recessive acantholytic dermatosis in Chesapeake Bay retrievers is associated with a mutation of which gene?
PKP1
Associated with loss of plakophilin-1 in desmosomal attachments as well as abnormal arrangement of desmoplakin and keratins 10 and 14
Which breed of cattle are affected by lethal hypotrichosis?
Holstein-Friesian
Japanese native
What are the clinical signs of congenital hypotrichosis of Hereford cattle?
Alopecia is variable and non-progressive. Calves have thin, pliable skin, extremely curly facial hair, and may have sparse pelage of thin soft curly, easily broken and epilated hairs, or be completely hairless. Some calves also have impaired hoof development.
What are the histopathological findings in congenital hypotrichosis of Hereford cattle?
The condition is characterised histologically by hypoplastic or degenerate hair follicles with vacuolation and necrosis of Huxley’s and Henle’s layers and abnormally large trichohyaline granules in Huxley’s layer. Most follicles contain fragmented hair shafts. Arrector pili muscles are reduced in number and frequently not associated with hair shafts.
A mutation in which gene is linked to X-linked hypohidrotic ectodermal dysplasia (XHED)?
Affected dogs have a triad of lesions: patterned hairlessness, an absence of atrichial sweat glands, and dental abnormalities (conically shaped teeth, anodontia).
Ectodysplasin 1 (ED 1)
A semi-dominant form of ectodermal dysplasia in congenitally hairless breeds of dog has been associated with which gene?
Forkhead box transcription factor family (FOXI 3)
What are the typical age of onset of clinical signs in colour dilution alopecia vs. black hair follicular dysplasia?
Colour dilution alopecia - few months to a few years of age
Black hair follicular dysplasia - few weeks to few months of age
Hairy shaker disease in lambs leads to what hair coat changes seen at birth?
To affect the hair coat, at what part of gestation does infection need to occur?
They have a long, straight, coarse coat.
This develops when infection occurs prior to day 80 of gestation.
Name a breed of dog affected by dermatomyositis other than Collies and Shetland sheepdogs
Beauceron Shepherd, Belgian Tervuren, and Portuguese Water dogs
What are the five subtypes of ischaemic dermatopathy?
- Canine familial dermatomyositis
- Juvenile-onset ischemic dermatopathy (similar to canine familial dermatomyositis except for the breed predispositions)
- Focal postrabies vaccination reaction
- Generalized vaccine-induced ischemic dermatopathy
- Adult-onset non–vaccine-induced generalised ischemic dermatopathy.
What are the early clinical lesions of dermatomyositis?
Small pustules, vesicles, papules, and nodules that evolve into erythematous, crusty, ulcerated, alopecic areas with hypopigmentation or hyperpigmentation.
What is the most consistently present histological abnormality in dermatomyositis?
The most consistently present histologic abnormalities are follicular atrophy and perifollicular inflammation that may be accompanied by perifollicular fibrosis.
In inherited collagen dysplasia, healing of wounds usually proceeds normally but results in what type of scar?
Characteristic thin, pale wrinkled scars resembling tissue paper.
Rank the species in order of severity of clinical signs of inherited collagen dysplasia: Dogs Horses Cats Sheep Cattle
Sheep > cattle > dogs > cats > horses
Collagen dysplasia (AKA dermatosparaxis) in cattle is due to a mutation in the gene for which enzyme?
Procollagen I N-proteinase (AKA procollagen aminopeptidase).
The enzyme that excises the amino-propeptide of type I and type II procollagens.
This leads to assembly of abnormal ribbon-shaped collagen fibrils lacking normal tensile strength.
Hereditary equine regional dermal asthenia (HERDA) affects which breed of horse?
Quarter Horse
Hereditary equine regional dermal asthenia (HERDA)
What are the clinical signs?
The affected horses have hyperextensible and loose fragile skin that results in poor wound healing and disfiguring scars.
At what age is hereditary equine regional dermal asthenia (HERDA) usually recognised?
6-12 months
What are the histopathological findings in cats with skin fragility syndrome?
Profound atrophy of dermal collagen fibres.
Collagen fibres are thin and disorganised. Hair follicles are in kenogen and markedly atrophied. The epidermis and other adnexa are also often atrophic. There may be orthokeratotic hyperkeratosis.
Which conditions have been associated with feline skin fragility?
Spontaneous and iatrogenic hyperglucocorticism Diabetes mellitus Cholangiohepatitis Hepatic lipidosis Cholangiocarcinoma Multicentric follicular lymphoma Feline infectious peritonitis Disseminated histoplasmosis Administration of various drugs, including megestrol acetate and other progestational compounds
What is proteoglycan a major component of?
The extracellular ground substance of the dermis
In cutaneous mucinosis of Shar-Peis, which cells excessively produce hyaluronic acid?
Dermal fibroblasts
Cutaneous mucinosis of Shar-Peis is associated with higher expression of which enzyme?
Hyaluronan synthase 2 (HAS2)
Which special stains can be used to better visualise mucin?
Alcian blue (stains mucin blue-green) Mucicarmine (stains mucin red)
Dermatosis vegetans is an inherited disorder affecting which species?
Pigs - autosomal recessive in Landrace
How do dermoid cysts form?
They are caused by defective epidermal closure along embryonic fissures, which isolates an island of ectoderm in the dermis or subcutis.
Dermoid cysts have been reported in dogs and which other veterinary species?
Horses (TBs)
Cattle (Angus)
Cats (DSH)
Keratinocytes are anchored to the basement membrane by hemidesmosomes and which other structure?
Focal adhesions
Which keratins are expressed in the basal keratinocytes and the suprabasal keratinocytes?
Basal - K5 and K14
Suprabasal - K1 and K10
What do focal adhesions and adherens junctions connect to?
Actin filaments - they are transitory adhesions
Which proteins mediate cell-substrate and cell-cell adhesion?
Integrins are receptors that mediate cell-substrate adhesion, whereas cadherins mediate cell-cell adhesion.
The keratin intermediate filaments in keratinocytes aggregate into what structure that connects with desmosomes, and therefore indirectly with adjacent cells?
Tonofilaments
Which keratins are acidic and which are basic?
K1-8 are basic (type II)
K9-20 are acidic (type I)
Which enzymes are thought to be responsible for desmosomal degradation and subsequent keratinocyte desquamation?
Hydrolytic enzymes, such as cathepsin B–like, carboxypeptidase, and acid phosphatase
Name three nutritional factors that can influence proper differentiation and maintenance of the epidermis?
Amino acids Vitamins A or B Zinc Fatty acids Copper
What are the histopathological findings in feline acne?
Histologically, the lesions consist of dilated sebaceous gland ducts, follicular keratosis with plugging and dilation, chronic periadnexal lymphoplasmacytic inflammation, and less commonly, luminal folliculitis and furunculosis.
Congenital digit hyperkeratosis occurs is which breeds of dog?
Irish terrier
Dogue de Bordeaux
Labradors with nasal parakeratosis develop verrucous brown scale and what other clinical sign on the nasal planum?
Variable depigmentation
What are the characteristic histological features of Labrador Retriever nasal parakeratosis?
Marked parakeratotic hyperkeratosis with serum lake formation with a band of lymphocytes and plasma cells in the superficial dermis. Other histopathologic findings include epidermal hyperplasia, neutrophilic and lymphocytic exocytosis, and pigmentary incontinence.
Which breed is most commonly affected by equine linear keratosis?
Quarter horse
Which body sites are most commonly affected by equine linear keratosis?
Neck, shoulder, and lateral thorax
What are the histopathological findings in equine linear keratosis?
Lymphocytic or lymphohistiocytic mural folliculitis, sometimes with follicular destruction. Multinucleated giant cells and eosinophils are variably present. Sebaceous glands can be secondarily effaced, and there is a variable amount of orthokeratotic or parakeratotic hyperkeratosis, with or without superficial perivascular non- suppurative inflammation.
Linear keratoses with a similar gross and histologic appearance to equine linear keratosis have also been described in which species?
Cattle
In equine cannon keratosis, which part of the cannon is affected?
The lesions consist of vertically oriented, moderately well-demarcated areas of alopecia, scaling, and crusting on the cranial surface of the rear cannon bones. Lesions are usually, not painful nor pruritic, are bilateral and persist for life.
Cutaneous horn can be associated with which infectious diseases?
In cattle, sheep, and goats, cutaneous horns may arise in lesions of dermatophilosis.
In the cat, multiple cutaneous horns on the footpads have been reported in association with feline leukemia virus (FeLV) infection.
Which breeds of dog are predisposed to sebaceous adenitis?
Akita Standard Poodle Samoyed Vizsla Lhasa Apso Havanese
What are the early clinical signs of sebaceous adenitis in short-coated dogs?
Patches of scaling and alopecia tend to appear on the ears and dorsum. These progress to annular areas of alopecia and scaling on the trunk and head.
Sebaceous gland destruction in sebaceous adenitis may progress more quickly in short- or long-coated dogs?
Long-coated dogs tend to have rapid and complete sebaceous gland destruction with little residual inflammation.
What are the three proposed mechanisms of pathogenesis in sebaceous adenitis?
(1) destruction of the gland resulting from immune-mediated mechanisms, leading to secondary hyperkeratosis
(2) a primary keratinization defect, resulting in increased amounts of follicular keratin blocking the sebaceous duct and causing inflammation of the gland
(3) a defect in the structure of the sebaceous duct or gland, resulting in inflammation directed at free sebum.
Vitamin A responsive dermatosis has been reported in Cocker spaniels and which other breeds?
Labrador
Miniature Schnauzer
What are the clinical signs of vitamin A responsive dermatosis?
Clinical lesions consist of hyperkeratotic plaques with follicular plugging and follicular casts on the ventral and lateral chest and abdomen. The dogs may have a greasy haircoat with ceruminous otitis.
What are the histopathological features of vitamin A responsive dermatosis?
The histologic features are marked follicular orthokeratotic hyperkeratosis, which is more severe than the epidermal surface hyperkeratosis.
In lichenoid-psoriasiform dermatosis of springer spaniels, which inflammatory cell predominates?
Histopathologic findings include lichenoid band of predominantly of plasma cells
Is basal cell apoptosis a feature of lichenoid-psoriasiform dermatosis?
No - they are present in low numbers
What are the histopathological features of ear margin dermatosis?
Histopathologic findings are characterized by marked orthokeratotic and/or parakeratotic hyperkeratosis with follicular keratosis and variable mild superficial perivascular dermatitis.
Do type 1 and 2 melanosomes contain melanin?
No
What shape are the melaonsomes producing eumelanin?
Round melanosomes produce eumelanins and elliptical melanosomes produces pheomelanins
Melanin pigments arise from the common metabolic pathway of conversion of tyrosine to 3, 4-dihydrophenylalanine (DOPA) and then oxidation to what?
DOPAquinone
Tyrosinase contains which mineral element and what does it do?
Copper
Catalyses tyrosine to DOPA
Melanotrichia can occur following insect bites in horses and which insult in white Merino sheep?
UV light exposure
In canine acanthosis nigricans, which layers of the epidermis are heavily melanised?
All layers of the epidermis are heavily melanised
What is the phenotype associated with Waardenburg syndrome?
White coats, blue or heterochromic irides and deafness
A type of Waardenburg syndrome in American Paint horses is fatal in foals due to what?
Aganglionic colon - foals develop colic and die shortly after birth
Piebaldism is associated with a mutation in the gene encoding for what?
C-kit tyrosine kinase or stem cell factor (the receptor ligand)
The c-kit tyrosine kinase receptor is associated with proliferation and survival of melanoblasts.
Vitiligo has been described in which dog breeds?
Belgian Tervuren, Doberman Pinscher, Newfoundland, Rottweiler, German Shepherd, Dachshund, German Shorthaired Pointer, and Old English Sheepdogs.
Which breeds are affected by “Dudley” or “snow” nose?
This is commonly seen in the Golden Retriever, Nordic breeds (Siberian Husky, Malamute), and yellow Labrador Retrievers.
Vitiligo has been reported in which breed of cat?
Siamese
Are melanocytes present in albinism?
Melanocytes are present and normally distributed but are defective in function and fail to synthesise melanin.
Cyclic haematopoiesis is associated with a mutation in which gene?
AP3
Hypopigmentation in horses can be associated with which diseases?
Onchocerciasis Culicoides hypersensitivity Ventral midline dermatitis Coital vesicular exanthema Rubber contact
Depigmentation in dogs has been reported with which infectious diseaes?
Leishmaniosis
M. persicolor dermatophytosis
What histopathological pattern is seen in uveodermatological syndrome?
Lichenoid interface with histiocytes and fewer neutrophils, lymphocytes and plasma cells. Basal cell apoptosis and vacuolar change are uncommon.
What are the four stages of decubitus ulcers?
In grade I, the lesion consists of focal erythema.
In grade II, an ulcer extends into the subcutis.
In grade III, the ulcer extends into the deep fascia, and the wound edges may be undermined.
Grade IV ulcers extend to bone, have under- mined edges, and possibly underlying osteomyelitis and septic arthritis
What disease consists of subcutaneous nodules composed of sheets of large macrophages in which the cytoplasm is filled with homogeneous eosinophilic spherules. These structures may resemble fungal organisms but are negative with fungal special stains such as periodic acid–Schiff. The spherules stain for endogenous peroxidase, thus establishing their identity as erythrocytes
Myospherulosis
What is the classical histopathological finding in injection site reactions?
Histologically, the classic injection site reaction is composed predominantly of nodular aggregates of lymphocytes arranged around a central core of caseous necrosis.
What are differential diagnoses for exuberant granulation tissue in the horse?
Sarcoid Habronemiasis Mycoses Pythiosis SCC
Which body sites are most commonly affected by cold injury?
Ears and tail of cats
Scrotum of male dogs and bulls
Tips of the ears, tail, and teats in cattle
Which type of thermal exposure is the most damaging?
Longer exposure to lower temperatures is more damaging than short exposure to higher temperatures
Define first degree burns
First-degree burns involve only the epidermis.
The heated areas are erythematous and edematous as a result of vascular reaction in the dermis, but vesicles do not form. The epithelial cells show no morphologic sign of injury, although there may be surface desquamation after a few days.
Define second degree burns
In second-degree burns, the epidermis and part of the dermis are damaged.
The cytoplasm of the epithelial cells is hypereosinophilic, and the nuclei are shrunken or karyorrhectic. Coagulative necrosis of the epidermis (Fig. 6-45) can occur in the absence of substantial dermal injury and often “wicks” down to involve the follicular epithelium. Vesicles and bullae form in the epidermis, often at the dermoepidermal junction.
Define third degree burns
In third-degree burns, the destructive effect of the heat extends full thickness through the epidermis and dermis, causing coagulative necrosis of connective tissues, vessels, and adnexa. Thermal injury causes thrombosis of blood vessels and vascular leakage, leading to the coagulative necrosis of more superficial tissues.
Define fourth degree burns
Fourth-degree burns are similar in character to those of third degree but penetrate below the dermis to and beyond the sub- cutaneous fascia. Heat in surface tissue is conducted to deeper tissues via the blood and lymph. The degree of injury may not be evident for several days after the insult occurred. Follicular and sweat gland damage continues for 24-48 hours.
In which type of thermal injury can you find eosinophilic, wavy elastin fibrils in the superficial dermis (“red spaghetti of Walder”)?
Radiant heat dermatitis (erythema ab igne)
Which affect of acute radiation injury is not reversible?
Damage to sebaceous glands is not reversible and leads to permanent scaling
Where do skin lesions start in dogs and cats with thallium toxicosis?
The pattern of skin involvement in cats and dogs is characteristic, beginning at the commissures of the lips or nasal cleft, occasionally on the ear margins, and expanding over the face and head.
What is characteristic about the mucous membranes in thallium toxicosis?
The mucous membranes are characteristically “brick-red” and may be ulcerated
What change to the surface and follicular epithelium is seen with thallium toxicosis?
Thallium severely alters the cornification process, and both the surface and external root sheath epithelium demonstrate marked parakeratotic hyperkeratosis
The presence of arsenic in the skin increases its susceptibility to what?
UV light damage
How does ischaemia occur in gangrenous ergotism?
Gangrenous ergotism is due to direct stimulation of adrenergic nerves supplying arteriolar smooth muscle. This produces marked peripheral vasoconstriction. Arteriolar spasm and damage to capillary endothelium leads to thrombosis and ischemic necrosis of tissues.
Macrocyclic trichothecene toxins produced by the fungus Stachybotrys spp. cause stachybotryotoxicosis, what are the skin lesions?
Ulcerative and necrotizing lesions of the skin and mucous membranes have been reported in horses, cattle, sheep, and pigs
What are the skin lesions seen in cattle with hairy vetch toxicosis?
Initial lesions consist of a rough coat with papules and crusts affecting the skin of the udder, teats, escutcheon, and neck, followed by involvement of the trunk, face, and limbs. The skin becomes less pliable, alopecic, and lichenified. Marked pruritus leads to excoriations.
What is photoallergy?
Photoallergy occurs when the photoproduct of an exogenous chemical acts as an antigen.
What is the difference between actinic and solar?
“actinic” is defined as ultraviolet (UV) rays from sunlight and UV lamps, whereas “solar” refers to radiation from the sun
Which solar radiation rays are:
100-400 nm
400-700 nm
700 nm - 1mm
UV light (100-400 nm) Visible light (400-700 nm) Infra- red light (700 nm to 1 mm)
What are the wave lenghts of UVA and UVB and which most often causes skin damage?
UVA 320-400 nm
UVB 290-320 nm
Most of the direct photobiologic reactions in the skin are induced by high-energy light in the ultraviolet radiation UVB range
Name three chromophores in the skin
Chromophores include keratin proteins, melanin, carotene, nucleic acids, peptide bonds, and some amino acids
Light absorbed by chromophores results in electron transfers and production of what?
Free radicals
UV light induces mutations of which gene in keratinocytes?
p53 tumour suppressor
Contributing to a proliferative advantage to mutated cells that is found in solar-induced actinic keratoses and squamous cell carcinomas in humans.
UVB radiation reduces the number of which non-keratinocyte epidermal cell?
Langerhans cells
Also impairs their antigen presenting function
What are the characteristic histopathological features of acute sun-induced epithelial damage?
Apoptotic keratinocytes, “sunburn cells,” arranged singly or in clusters or bands in the outer stratum spinosum
In severe sun-induced burns, lesions include spongiosis, vacuolation of keratinocytes, loss of the granular layer and…
Vesiculation, marked vascular damage, erythrocyte extravasation, and neutrophilic exocytosis
UV irradiation causes transient erythema - how?
Probably from a direct heating effect and the photobiologic effects of UVB acting directly on dermal capillaries
UV irradiation causes delayed erythema - how?
The delayed erythema reaction may be due to direct damage to endothelial cells or the release of cytokines from the radiation-damaged keratinocytes
What adaptive epidermal responses are seen with UV radiation?
Epidermal hyperplasia
Altered melanin pigmentation
How does melanin help protect the skin from UV radiation?
Melanin both absorbs and scatters UV radiation and, being able to trap free radicals, is important in minimising the deleterious effects of incident photons
In solar dermatitis in dogs, early lesions of scaling and erythema evolve into what?
Thick, lichenified, erythematous, crusted patches and plaques and haemorrhagic bullae.
What is the most consistent histologic finding in dogs with chronic solar dermatitis?
A narrow, hypocellular, pale-staining band of collagen along the dermoepidermal junction. This change may be present prior to clinical signs of actinic dermatitis and may be used as an indicator of solar damage.
Can actinic comedones be seen in dogs with chronic solar dermatitis in the absence of other skin lesions?
Yes
Increased expression of which enzyme appears to play an early role in actinic keratosis and SCC?
Cyclooxygenase-2 (COX-2)
What does COX-2 over-expression lead to?
Increased expression of prostaglandin E2 (PGE2). Activation of the COX-2/PGE2 pathway induces cell proliferation, inhibits apoptosis, and promotes angiogenesis and carcinogenesis.
COX-2 expression in SCC has been shown in rats, people and which other species?
Cats, dogs and horses
Solar elastosis appears in H&E- stained sections as scattered or agglomerated, thick, irregular, basophilic degenerate elastic fibres, which special stains can be used to demonstrate these changes?
Silver stains
What are the histological features of chronic solar keratosis?
Pronounced epidermal hyperplasia with dysplasia, orthokeratotic and parakeratotic hyperkeratosis, perivascular mononuclear cell infiltrates, and dermal scarring, but seldom develop significant solar elastosis, as typifies human solar keratoses. Can also develop cutaneous horn.
In photosensitisation, the energy from the absorbed light leads to tissue injury by reacting directly with molecular oxygen, producing what?
Reactive oxygen intermediates, such as superoxide anion, singlet oxygen, and hydroxyl radical
In photosensitisation, oxygen free radicals are formed by absorbed light energy and what other route?
Oxygen free radicals may also be formed indirectly, as the result of calcium-dependent, protease-mediated activation of xanthine-oxidase in the skin
In photosensitisation, release of reactive oxygen species initiates chain reactions that lead to what?
Mast cell degranulation and damage to cell membranes, nucleic acids, proteins and subcellular organelles, particularly lysosomes and mitochondria
What is primary photosensitisation?
Ingestion of plants or drugs containing photoreactive substances
What is type II photosensitisation?
Inability to properly metabolise heme pigments leads to build up of haematoporphyrins
What is type III photosensitisation?
Abnormal build up of phylloerythrin (degradation of chlorophyll) due to liver disease
Most common form in domestic animals
What is type IV photosensitisation?
Idiopathic
What are the initial lesions of photosensitisation?
Erythema and oedema (odema can be prominent in sheep - muzzle swelling can cause dyspnoea -‘big head’)
What are the histopath features of photosensitisation?
- Coagulative necrosis of the epidermis and possibly the follicular epithelium, adnexal glands, and superficial dermis.
- Subepidermal clefts or vesicles and dermal odema.
- Endothelial cells of the superficial, mid, and occasionally deep dermal vessels are often swollen or necrotic.
- Fibrinoid degeneration of vessel walls and thrombosis may be present. - Initially, inflammation is sparse, but soon the lesions are infiltrated by neutrophils.
The majority of photosensitising plants contain pigments belonging to which families?
The helianthrone or furocoumarin family of pigments
Which plants contain helianthrone pigments?
St John’s wort
Buckwheat
Which plants contain furocoumarin pigments?
Spring parsley
Bishop’s weed
Dutchman’s breeches
How do furocoumarin pigments differ from helianthrone pigments?
The furocoumarin pigments also induce corneal oedema and keratoconjunctivitis
Bovine congenital hematopoietic porphyria is the result of a deficiency in which enzyme?
Uroporphyrinogen III cosynthetase, a key enzyme in heme biosynthesis.
Red discolouration of which tissues occurs in bovine congenital hematopoietic porphyria?
Teeth (dentin) and bone (fluoresce in UV light)
Pigment is deposited in other tissues but is also visible in lungs, spleen and kidney
How is urine affected in bovine congenital hematopoietic porphyria?
It is amber to brown, darkens on exposure to light, and fluoresces bright red on exposure to UV radiation
What are the histopath lesions of bovine congenital hematopoietic porphyria?
Subepidermal clefts, hyalinization of dermal capillary walls, and a minimal infiltrate of inflammatory cells. The basement membrane zone lines the base of the subepidermal cleft, in some instances covering small projections of dermal papillae (festoons).
Skin biopsy from a horse; arrows point at large intracytoplasmic inclusion bodies. What is the diagnosis?
Molluscum contagiosum virus
