Final- Integument Flashcards

Question

Acute Solar injury

Answer 1

• Acute UV light exposure leads to “sunburn” – _erythema_ leads to _blistering/vesicles_ leads to _sloughing of necrotic skin_ – potentially due to uv‐mediated endothelial damage and cytokine production MDx: chronic locally extensive ulcers

Answer 2

• Chronic (_years of_) UV light exposure leads to **“solar/actinic keratosis”** – Chronic injury leads to epidermal hyperplasia and dermal fibrosis and elastosis – Increased risk for neoplasia due to direct DNA injury and subsequent mutations- SQUAMOUS CELL CARCINOMA MDX: epidermal hyperplasia, dermal fibrosis and elastosis increased risk for neoplasia due to direct DNA injury and subsequent mutations

Answer 3

dermal fibrosis and comedones ## Footnote The epidermis is thickened by acanthosis, and three comedones (follicular distention and hyperkeratosis) are present. If comedones rupture, a large amount of endogenous foreign material (stratum corneum, hair shafts, and sebum) is released into the dermis, causing a foreign‐body inflammatory response. Bacteria are also released and cause a secondary bacterial infection.

Answer 4

• Caused by exposure to excessive heat – hot liquids, flames, friction, electricity, heating pads, blow dryers, drying cages, and lightning _1st degree_ – epidermis – Reddened/darkened necrotic epidermis – Complete healing _2nd degree_ – epidermis and dermis – Vesicle formation – Some adnexa are preserved allowing epidermal _3rd degree_ – full thickness epidermis and dermis +/‐ subcutis – Sloughing of necrotic tissue, followed by granulation tissue – Scar; life threatening (fluid/protein loss and portal for sepsis) Examples: 1st degree burn from my savvy cooking skills- Mdx: focal acute epidermal degeneration and necrosiss regeneration with some scarring

Answer 5

Thermal burn, full thickness (third‐degree) skin, dog. A, There is necrosis of the epidermis (arrow), follicular epithelium, and dermis. Because of increased capillary permeability, fluid has accumulated between the dermis and epidermis, forming vesicles (V). H&E stain. B, The dry necrotic skin is the site of the burn (arrow).

Answer 6

• Caused by body or wound secretions, application of drugs, exposure to acids, alkalies, soaps, detergents, or irritant plants Most cases mild (“irritant”) Exposure via direct application – Must penetrate hair and protective epidermal layers – Adsorptive medium may facilitate • Main issue differentiating vs contact hypersensitivity dermatitis

Answer 7

**THIS TYPE IS HISTOLOGICALLY AND GROSSLY DISTINCT!** • Pathogenesis thought to involve _type IV hypersensitivity_ towards antigens on the surface of keratinocytes inducing apoptosis – induced via antigenic mimicry from drug administration, underlying infection, neoplasia, dyes/preservatives in pet foods? – Histologically distinct – Widespread coalescing erythematous macules(spots that are not elevated or depressed, but they are a different color) that leads to vesicles and ulcers _EM_ – Milder macules leads to vesicles and ulcers – Single cell apoptosis +/‐ lymphocyte satellitosis _TEN_ – More severe – Sheets of apoptotic/necrotic cells resembling a burn

Answer 8

Erythema Multiforme & Toxic Epidermal Necrolysi

Answer 9

Tips for differentiating - Look for ‘cardinal signs of inflammation’ – erythema, edema, exudate, heat, pain; + itching! - If there are pustules/crust, there is an inflammatory component to the lesion - Depigmentation – immune mediated inflammatory lesions - If inflammatory infiltrate is severe enough, will see papules, plaques, nodules, but disorders of growth (neoplasia) can also result in these changes

Answer 10

_Early_ Gross Features of Dermatitis – Edema – Erythema – +/‐ pustules, crust, vesicles _Later_ – Scaling – Ulceration – Alopecia – Lichenification – Pigmentary change – Fibrosis/scarring

Answer 11

Inflammation and Repair- DERMATITIS – Suppurative/Pustular/Exudative/Neutrophilic – bacterial, auto‐immunity – Proliferative – viral – Vesicular – viral, auto‐immunity – Granulomatous – ‘higher’ bacteria, mycobacteria, fungal, foreign substance – Eosinophilic – allergy, parasitic – Interface – auto‐immunity- HISTOLOGICAL DX

Answer 12

• “pus in the skin” – usually bacterial infection involved

Answer 13

**_• Superficial – epidermis and hair follicles_** – Examples * Canine superficial spreading pyoderma / Bacterial folliculitis * Impetigo (superficial pustular dermatitis) Greasy pig disease Dermatophilosis **_• Deep – deep dermis_** – Examples • Bacterial furunculosis • Abscesses

Answer 14

Dog with superficial spreading pyoderma, a superficial pyoderma with bacterial folliculitis

Answer 15

Dog with chin acne, a deep pyoderma with bacterial furunculosis hair explodes and bacteria then forms chin acne

Answer 16

Pores (follicular openings) Hematogenous spread- less common Direct entry through damaged skin

Answer 17

Allergy Disorders of keratinization (seborrhea) Immunodeficiency Anatomic predisposition

Answer 18

- Thin stratum corneum, - lack of lipid seal of hair follicles, - high skin pH

Answer 19

**Often involve Staphylococcus spp.** Exception: opportunistic gram negatives, and cases of dermatophilosis Produce _exfoliative toxins_ that cause intraepidermal splitting

Answer 20

(Superficial pustular dermatitis)- bacteria colonize WHEREVER in the epidermis * Nonfollicular pustules which develop into crusts * Prepubescent puppies – healthy otherwise * Adults – look for underlying disease can be from poor over all condition

Answer 21

Puppy with pustular dermatitis “impetigo”

Answer 22

• Skin fold pyoderma Intertrigo • Pathogenesis: closely apposed skin surfaces → frictional trauma → moisture → opportunistic bacterial infections You need histo to confirm dx

Answer 23

Intertrigo

Answer 24

Pyotraumatic Dermatitis (“Hot Spots”) • Very common in dogs Pathogenesis • **_Self trauma_** ----\>bacterial infection Gross: moist, alopecic, slightly raised, red well‐ circumscribed lesions -----\> ulceration/crusting • Underlying pruritis – especially flea allergy dermatitis! **Usually Staph!**

Answer 25

crusts and papules

Answer 26

Papule or if it gets bigger nodule

Answer 27

Pyotraumatic Dermatitis (“Hot Spots”)

Answer 28

Pyotraumatic Dermatitis (“Hot Spots”)

Answer 29

Fatal in neonatal pigs Caused by **Staphylococcus hyicus** Gross: erythema--\>pustules---\>crusts • Predisposing factors – other skin lesions, poor nutrition/husbandry, lacerations

Answer 30

Greasy Pig Disease (Exudative Epidermitis)

Answer 31

* Caused by **_Dermatophilus congolensis_**(Train tracks!) – gram positive filamentous bacteria which subdivide longitudinally and transversely * Lesions on back or distal extremities * Stimulate neutrophilic exocytosis: pustules--\>exudate--\>matting of hair/wool ---\> alopecia _Predisposing factors:_ – **Wet weather** in humid climates (“rain rot”) – prolonged wetting of skin/hair/wool allows penetration of epidermis by “zoospores”

Answer 32

Dermatophilosis

Answer 33

Also called ‘lumpy wool’ in sheep Dermatophilius

Answer 34

Usually secondary condition **Bacterial infection of superficial follicles and adjacent skin- Follicultis- when we have inflammation of the hair follicle before the hair follicle ruptures** **furunculosis- when the hair follicle ruptures** _Gross:_ scaling, erythematous macules (often circular--\>ring shaped), papules, pustules, crusts, epidermal collarettes, alopecia _DDx:_ – Dermatophytosis (‘ring worm’) – Demodicosis _Diagnostics:_ – Cytology of pustule/crust -------------neutrophils with cocci – Woods lamp – Fungal culture – Skin scraping

Answer 35

Canine superficial spreading pyoderma

Answer 36

Fig. 17‐27 Folliculitis and furunculosis, skin, haired, dog. A, The wall of the follicle has become disrupted, resulting in the release of follicular contents (a hair shaft, stratum corneum of the follicle, and exudate) into the dermis. The follicular lumen also contains numerous coccoid bacteria (arrow). The hair shaft has variably sized and shaped melanin pigment granules, indicating that this dog also has coat color dilution. H&E stain. B, A circular area of erythema, scaling, and crusting is caused by follicular inflammation and rupture (furunculosis). The inflammation in the perifollicular dermis has extended into the surrounding dermis and formed a draining sinus to the epidermal surface. The exudate on the surface has dried to form a crust.

Answer 37

Two Conditions Grossly Indistinguishable from Canine Superficial Spreading Pyoderma (because they also have folliculitis; erythematous macules---\>alopecia and scaling) **Demodicosis** Cause: Demodex spp. mite Lesion vary by host/mite species – Distribution on body – Neutrophilic to granulomatous (exudative vs nodular grossly) • In dogs – Localized form – face, forelegs – Generalized form – Adult‐onset demodicosis is often associated with systemic disease such as neoplasia, endocrinopathy, or immunosuppressive therapy

Answer 38

Two Conditions Grossly Indistinguishable from Canine Superficial Spreading Pyoderma (because they also have folliculitis; erythematous macules--\> alopecia and scaling) Dermatophytosis * Cause: Epidermophyton, Microsporum, and Trichophyton spp. (keratinophilic fungi) * **Contagious(only one that is)** – acquired by contact with scales shed from infected animals * Colonize keratin, do not need to invade tissue to cause disease * Self‐limiting in healthy animals, can become chronic/generalized in immunocompromised animals _Predisposing factors:_ – Youngorimmunosuppressed – Hot/humid environments Cattle have a different lesion!

Answer 39

There is a leukocyte infiltrate of the epidermis... The pathological process is likely _inflammatory_ Differential Diagnoses?? What can we do to determine the cause? Skin scraping: • No mites or fungus seen Wood’s lamp: • No fluorescence Fungal culture: no growth Cytology of a pustule: • Eosinophils **• Some bacteria, but not within cytoplasm of leukocytes, and not many neutrophils- NOT A LOT OF BACTERIA THOUGH!**

Answer 40

Acantholytic keratinocytes consistent with Pemphigus foliaceous MDx: Eosinophilic pustular dermatitis with intralesional acatholytic keratinocytes

Answer 41

* “Pemphigus” – group of auto‐immune diseases involving type II hypersensitivity against cell adhesion proteins (desmosomes) * PF is the most common and milder form of pemphigus (reported in horses, dogs, cats and goats) – others are rare but covered in text * Often involves face, ears, footpads, clawbeds * Vesicles, pustules, crusts, ulcers * _Can be spontaneous, drug‐induced, or associated with allergic skin disease_

Answer 42

Something is being added to the epidermis... The pathological process is likely a disturbance of growth or inflammatory- MDx: papular dermatisis **_Proliferative- Viral etiology_** Differential Diagnoses?? What can we do to determine the cause? Skin scraping: • No mites or fungus seen Cytology (aspirate a papule): * A few lymphocytes, some keratin * Staph. sp

Answer 43

Thickening of the epidermis(2-3x normal) Histopathology report: Mdx: Proliferative dermatitis with “ballooning degeneration” & intracytoplasmic inclusion bodies Comment: _Consistent with swine-pox infection_

Answer 44

Pox Viruses * Sequence of lesions: macule → papule → vesicle → umbilicated pustule → crust → scar * Poxviruses have a gene whose product is similar to _epidermal growth factor → epidermal hyperplasia_ * Many cutaneous lesions only, some systemic and fatal * Some are foreign animal diseases

Answer 45

Lamb with contagious exanthema, early papular to vesicular phase pox virus

Answer 46

Lambs with contagious exanthema, late crusty phase

Answer 47

Something is injuring keratinocytes... The pathological process is likely degeneration&necrosis or inflammatory Differential Diagnoses?? * Early herpesvirus * Early poxvirus Viruses!! • Vesicular diseases – FMD, VSV, SVD, VES What is the next best step in our diagnostic process?? This was VSV. * The only sure way to distinguish these diseases is by laboratory testing * Producers and private practitioners, are the first line of defense against these economically devastating diseases. * WHENEVER YOU SEE ULCERS – LOOK FOR VESICLES!

Answer 48

Herpesviruses can cause cutaneous vesicles!

Answer 49

Something is being added to the epidermis... The pathological process is likely a **disturbance of growth or inflammatory** Differential Diagnoses?? What can we do to determine the cause? Skin scraping: • No mites or fungus seen – how helpful is this with nodular disease? NOT VERY HELPFUL! Cytology (aspirate a papule): * Macrophages; inflammatory, cause not apparent * Staph. sp

Answer 50

Histopathology report Multifocal granulomatous dermatitis No infectious agents or foreign material seen with special stain

Answer 51

Pathogenesis is not understood- treat with immunosupressives * Juvenile sterile granulomatous dermatitis and lymphadenitis * Sterile pyogranuloma syndrome (idiopathic sterile granuloma and pyogranuloma) Canine reactive histiocytosis Canine Langerhans’ cell histiocytosis Feline dendritic cell histiocytosis Idiopathic sterile nodular panniculitis Xanthoma (xanthogranuloma) * Equine generalized granulomatous disease (see the section on Vetch Toxicosis and Vetch‐Like Diseases) * Feline nutritional pansteatitis (see the section on Vitamin E Deficiency Don't need to memorize all of these! Just know that we don't quite know why this happens

Answer 52

* Rare * Esp. dogs Pathogenesis • Pathogenesis – cause unknown – Caused by fastidious unrecognized organisms? – Abnormal immune response to unidentified microbial antigen? – Variant of histiocytic neoplasia? **• Diagnosis of exclusion**

Answer 53

• Uncommon Fungal dermatitis * Pythium, Lagenidium spp. * **“Swamp Cancer”** ‐ clinically resembles neoplasia...invasive lesions, involvement of regional lymph nodes * Dx with Culture + PCR – why?

Answer 54

* Bacteria introduced by _traumatic injury_ * Nocardia and Actinomyces sp. * Can form _large clumps_ (grossly evident as ‘sulfur granules’) * Gross ‐ Nodules, ulceration, draining sinuses, involvement of underlying bone(Actinomyces bovis- lumpy jaw)

Answer 55

Mycobacterial Dermatitis Feline leprosy * Cause ‐ Mycobacterium lepraemurium, obligate intracellular organism (potentially other strains) * Cats in cold, wet areas * Transmission unknown – biting insects? * FIV/debilitation may be predisposing factors * Numbers of mycobacteria in lesions can be low – might not see on histo * DOES NOT GROW IN CULTURE – Must use PCR – Can not get sensitivity results

Answer 56

Mycobacterial Dermatitis Opportunistic mycobacteriosis • Cause – **“atypical mycobacteria”, facultative saprophytes (inhabitants of soil, water, and decomposing vegetation)** – Rapid‐growing (more common) – M. fortuitum, M. smegmatis, M. chelonae, M. abscessus, M. thermoresistible Dermatology for Animals – Slow‐growing – M. avium‐intracellulare complex, M. kansasii, M. ulcerans • Infection tends to occur via wound contamination or traumatic implantation Usually localized, but can disseminate Can do culture and sensitivity

Answer 57

* Cause – saprophytic mycobacteria * Transmission – fly bites? * Nodules involving dorsal pinna, less commonly other distal extremities- EARS IN DOGS Short coated breeds, esp **_Boxer_** Self‐limiting in immunocompetent dogs but may last months • Difficult to culture, may need PCR; but usually can find organisms with histo

Answer 58

Mycobacterial Dermatitis Canine Leproid Granuloma BOXER!

Answer 59

Puppy Strangles (Juvenile sterile granulomatous dermatitis) Day 1 – pustules, enlarged LN * Pups\<4mosold * One or more in litter * _Pathogenesis unknown_ * Gross – pustules, nodules, swelling of face, ears, mucocutaneous junctions * Histo – (pyo)granulomatous dermatitis and panniculitis +/‐ lymphadenitis * Fever, joint pain STARTS WITH PUSTULES ON THE FACE!

Answer 60

Puppy Strangles

Answer 61

“Lick Granuloma” Acral lick dermatitis Common in dogs Cause – persistent licking/chewing * Underlying factors – boredom? Sensory polyneuropathy? * Gross – extremities; circumscribed, hairless, and ulcerated * Histo – **Not really a granuloma!** – Epidermal hyperplasia, granulation tissue, fibrosis

Answer 62

“Lick Granuloma” Acral lick dermatitis

Answer 63

eryethema on the ventrum and inter-digitally The pathological process is likely inflammatory BECAUSE IT'S ITCHY! Skin scraping: • No mites or fungus seen Bacterial Culture: • Staph. sp Fungal culture: • negative

Answer 64

Histo report: Eosinophilic dermatitis with epidermal hyperplasia; no cause evident. Consistent with ALLERGIC SKIN DISEASE. Must distinguish clinically.

Answer 65

Atropy in a dog: MDx: chronic dermatitis

Answer 66

Web Fig. 17‐2 Atopic dermatitis, skin, dog. A, This Golden retriever has erythema, alopecia, and erosions in the skin around the eye and muzzle. The lesions are caused by self‐trauma from rubbing and scratching as a result of pruritus. DX WITH INTRADERMAL SKIN DISEASE TYPE I HYPERSENSITIVITY TO ENVIRONMENTAL ALLERGENS

Answer 67

Contact Dermatitis • Pathogenesis: Type IV hypersensitivity reaction; exposure via direct contact – Plastics in food bowls – Dyes in carpets – Plant residues in bedding * Low molecular weight haptens present in chemicals require binding to cell‐associated proteins prior to being recognized by CD8+ (cytotoxic) T lymphocytes * Distribution ‐ depends on site of contact, often in poorly haired areas

Answer 68

Insect Bite Hypersensitivity • Pathogenesis: Type I and/or IV hypersensitivity reaction • Examples – Culicoides saliva ‐ horses – Flea saliva ‐ dogs and cats – Mosquito saliva ‐ cats • Distribution: depends on areas favored by insect, but can become generalized – Culicoides – tail base, withers, head – Fleas – tail base (dog), neck (cats) – Mosquito – nose and face * Gross: often includes papules * Histo: may have eosinophilic pustules, folliculitis, or granulomas IN the picture:Horse with culicoides hypersensitivity (above); Cat with mosquito bite hypersensitivity (below)

Answer 69

Dog with flea bite hypersensitivity; Remember: pyotraumatic dermatitis (secondary self‐trauma associated pyoderma) very common with this condition.

Answer 70

“Miliary dermatitis” in Cats- _Clinical Term_ not patholgical term Not a disease, a pattern of lesions. Small crusty erythematous papules. Commonly seen in cats with allergic skin disease.

Answer 71

ALSO not a disease, a pattern of lesions. Indolent ulcer – ulcers on upper lips. Eosinophilic plaque – discrete red to ulcerated plaques on abdomen or medial thighs. Eosinophilic granuloma – nodules (may be ulcerated) on thighs, face or mouth. Commonly seen in cats with allergic skin disease.

Answer 72

“Eosinophilic granuloma complex” in Cats

Answer 73

“Eosinophilic granuloma complex” in Cats

Answer 74

“Eosinophilic granuloma complex” in Cats

Answer 75

* Grossly similar to non‐eosinophilic granulomas * Often see collagenolysis – due to proteolytic enzymes of eosinophil granules? _• Causes:_ – Parasite reaction – Insect bite hypersenstivity – Foreign body reaction – Underlying mast cell neoplasia

Answer 76

Degenerate collagen fibers within an eosinophilic granuloma

Answer 77

Case of cutaneous habronemiasis (**“Summer sores**”): Cutaneous eosinophilic granulomas caused by larval migration of _Habronema or Draschia sp. deposited into a wound by house or stable flies_ Fig. 17‐59 Cutaneous habronemiasis, Habronema sp., skin, horse. A, Face. Multiple coalescing nodular granulomatous and ulcerated areas are present on the skin of the medial canthus, skin immediately ventral to the eye, and the skin of the lateral surface of the face. Lesions of cutaneous habronemiasis develop in areas of the skin that are traumatized (often the legs) or in soft moist skin (around the genitalia or eyes). In this case, moisture from ocular secretion (tears) may have predisposed to bites of house or stable flies, with subsequent emergence and migration of Habronema sp. larvae into the dermis. B, Note sections of larvae within necrotic debris bordered by macrophages and mixed inflammation including eosinophils. H&E stain.

Answer 78

Discoid Lupus Erythematosis * 2nd most common autoimmune skin disease * Induction/exacerbation by UV light * Dorsal **nose** and nasal planum \>\>\> pinnae, lips, periocular region \>\>\> oral mucosa * Gross: depigmentation, erythema, scaling, erosion, ulceration, and crusting Dermatology for Animals * Histo: interface dermatitis * DDx: Uveodermatologic syndrome – auto‐ immune disease against dermal and uveal melanocytes; esp arctic breeds Uveodermatological Syndrome in an Akita

Answer 79

Mononuclear leukocytes infiltrate at the epidermal junction and obscure the basal lamina Basal keratinocyte apoptosis There are several other immune-mediated dermatoses with similar interface dermatitis.

Answer 80

Pigmentary incontinence

Answer 81

- Discrete reddened areas (hemorrhage)! - Lesions follow a linear pattern - Lesions are in geometrical shapes (indicating mapping to a vascular supply) - Vascular lesions which result in ischemia -----\>see gross features of degeneration/necrosis

Answer 82

1. increased vascular permeability 2. decreased oconotic pressure(loss of protein) 3. increased hydrostatic pressure(hypertension or chronic congestion) 4. lymphatic obstruction

Answer 83

MDx: Multifocal cutaneous ecchymotic hemorrhages Cause = Primary hemostasis defect (Vasculitis vs thrombocytopenia) hemorrage WILL NOT BLANCH OUT

Answer 84

No blood supply to the area- this is how you get the pigmentation _Gross:_ – Sharply demarcated geometrical shaped dark red to blue area – As time goes by becomes firm, dry, sunken, darkened (features of necrosis begin to predominate over hemorrhage) _Causes:_ – Vasculitis _Gram negative septicemias_ - Erysipelothrix rhusiopathiae, Salmonella, Pasteurella, E. coli E. coli shiga toxin 2e (damages endothelium) “Edema Disease” _Spider/snake bite_ hypersensitivity Drug reaction Secondary to ulceration – Frost bite- distial extremidities – Toxins causing extreme vasoconstriction (ergot)

Answer 85

Pig with “diamond skin disease”. MDx: Cutaneous infarcts Cause: E. rhusiopathiae bacteremia, associated thrombosis & vasculitis.

Answer 86

MDx: Multifocal cutaneous infarcts. Disease: Diamond skin disease Cause: Erysipelothrix rhusiopathiae DDx: Salmonellosis (+ African swine fever, hog cholera viruses) Sharp demarkcation on the ears

Answer 87

MDx: Vasculitis and thrombosis (with cutaneous hemorrhage and necrosis) see a lot of hemmorrage

Answer 88

Erysipelothrix rhusiopathiae infection, skin, haired, pig. B, The epidermis and dermis are necrotic from infarction. The only normal dermis and epidermis are at the extreme left. H&E stain.

Answer 89

pig with “diamond skin disease”. MDx: Cutaneous _ecchymotic hemorrhages_ Cause: E. rhusiopathiae bacteremia and associated vasculitis.

Answer 90

Pathogenesis: Type III hypersensitivity immune-mediated vasculitis Cause: Streptococcus equi infection (rarely with other infections or vaccinations) Gross: Red or purple macules or patches (hemorrhage or infarct) in the skin or mucous membranes

Answer 91

Purpura hemorrhagica

Answer 92

Horses with purpura hemorrhagica. Ecchymotic hemorrhages (above) and subcutaneous edema (below).

Answer 93

Cause: exposure to cold temperature Pathogenesis: – Formation of ice crystals which physically disrupt cells – Vasoconstriction and endothelial damage---\> reduced blood flow---\> thrombosis ---\>infarction Lesions in cold exposed extremities Fig. 20-30 Auricular infarction, frostbite, goat. Note that the distal (upper) half of the ear has **_dry gangrene_** from frost-bite.

Answer 94

Fig. 20-30 Auricular infarction, frostbite, goat. Note that the distal (upper) half of the ear has dry gangrene from frost-bite.

Answer 95

Something is being added to the dermis... The pathological process is a vascular disorder What can we do to determine the cause? These are called WHEALS. These are trascient. T_hese are from a vascular disorder from edema._ These are a Hyper I and III hypersentivity. These are itchy. Wheal = Elevated, irregular-shaped area of cutaneous edema; solid, transient

Answer 96

Wheal = Elevated, irregular-shaped area of cutaneous edema; solid, transient (arrows)

Answer 97

Dogs, horses Localized areas of edema – Urticaria – superficial dermis – Angioedema – dermis + subcutis- when head is swelling Pathogenesis: Type I and III hypersensitivity; mast cell degranulation  focal edema, congestion, pruritis Triggers – foods, drugs, antisera, insect stings Histo – subtle (don’t waste your time!)

Answer 98

MDx: multifocal cutaneous edema and congestion

Answer 99

My dog “Jessie” with hives in St Kitts (in the middle of the night) due to suspected centipede bite reaction

Answer 100

Food Allergy Contact Hypersensitivity Insect Bite Hypersensitivity * Distribution of lesions vary * Gross – Lesions due to self‐inflicted trauma: erythema, alopecia, excoriation – Lesions due to secondary pyoderma: papules, pustules, crusts – Lesions due to chronicity: lichenification, hyperpigmentation, scaling Dog with atopy. • Histo – Lymphocytic and eosinophilic dermatitis

Answer 101

* Affects 10‐15% of dogs * Pathogenesis: Type I hypersensitivity to environmental allergens (“inhalant allergy”) Diagnose with intradermal skin testing Distribution ‐ ventrum, face, distal extremities

Answer 102

MDx: Generalized subcutaneous edema.

Answer 103

Things that injure cells at a critical stage of development. The defect depends on tissue tropism and timing. Genetic defect – inherited mutation, spontaneous somatic mutation In utero infection – BVD, bluetongue, border disease, akabane, panleukopenia, classical swine fever In utero exposure to teratogens – toxic plants, griseofulvin in cats

Answer 104

Less than the normal amount of hair Hereditary most common More susceptible to environmental extremes and infections

Answer 105

Calf with hypotrichosis (“Singy calf”) Due to in utero BVD infection born without hair

Answer 106

Collagen Dysplasia (Cutaneous Asthenia, Dermatosparaxis, Ehlers-Danlos) Fig. 17-36 Collagen dysplasia, skin, dog. A, The skin is hyperextensible. In this dog, the skin can be stretched more than the skin of a normal dog. B, The collagen bundles are irregular in size and shape and are arranged haphazardly. The abnormally formed collagen is responsible for the hyperextensibility of the skin, which predisposes to tearing with normal handling and activity. H&E stain. C, Deeper level of the sample shown in B. Collagen bundles are stained blue. The variation in diameter and shape of the collagen bundles and their haphazard arrangement is accentuated with this stain. Masson's trichrome stain.

Answer 107

Epitheliogenesis Imperfecta **fatal due to 2ndary infections** skin has not developed

Answer 108

Ichthyosis calf extra thick stratum corneum

Answer 109

_Endocrine disorders_ – Hypothyroidism – Hyperadrenocorticism – Hyperestrogenism (sertoli cell tumor) – Alopecia X _Hair cycle abnormalities_ – Postclipping alopecia – Telogen effluvium – Antimitotic drugs - chemotherapeutics, immunosuppressants Excessive grooming – feline psychogenic alopecia **_Self-trauma (pruritis_**- most common) – ectoparasites, dermatitis of any cause, but particularly allergic skin disease Autoimmune - alopecia areata (antibodies made against hair follicle)- only one that is HISTOLOGICALLY DISTINCT General poor nutrition - hairs are produced weak Hyperkeratosis - interferes with the hair follicle decreasing hair production Cicatricial alopecia (scar)

Answer 110

Fig. 17-65 Truncal alopecia, hyperadrenocorticism, skin, dog. A, Note the alopecia, distended abdomen, and thin skin in which blood vessels are faintly visible (arrow). The distended abdomen and visibility of blood vessels are a result of protein catabolism and loss of muscle and dermal collagen, respectively. The distended abdomen and thin skin with greater visibility of blood vessels in conjunction with symmetric alopecia suggest that a catabolic endocrine disease, such as hyperadrenocorticism, is likely. B, Atrophy of dermal collagen fibers is so severe that the collagen has almost disappeared, leaving the adnexa and arrector pili muscles readily visible. Hair follicles are in the telogen (resting) stage of the hair cycle. H&E stain.

Answer 111

Fig. 17-67 Symmetric alopecia and hyperpigmentation, hyperestrogenism (iatrogenic from diethylstilbestrol therapy), skin, dog. A, Note the symmetric alopecia and hyperpigmentation over the caudal dorsal trunk and caudolateral hind legs. In male dogs, the symmetric alopecia in conjunction with enlargement of nipples, pendulous prepuce, and attraction of other male dogs suggest the possibility of hyperestrogenism. B, Note epidermal orthokeratotic hyperkeratosis (arrowhead), follicles dilated with keratin (F), and small atrophic follicles (arrows) in the telogen (resting) stage of the hair cycle. H&E stain.

Answer 112

**_Epidermal Hyperplasia_** _Acanthosis –_ increased thickness of stratums basale and spinosum ------ very active areas which is why they thickenss _Hyperkeratosis –_ increased thickness of stratum corneum – Parakeratotic - nuclei retained – Orthokeratotic - anuclear

Answer 113

**Hyperkeratosis** Gross – scaling “seborrhea” _Primary (Idiopathic seborrhea) -_ especially Cockers, Springers, Westies _Secondary_ – Endocrine imbalances – hyperadrenocorticism, hypothyroidism, hyperestrogenism – Chronic dermatitis – especially allergy and ectoparasitism – Zinc responsive

Answer 114

Inherited disorder of keratinization or cornification Pathogenesis: thought to involve hyperproliferation of the epidermis, hair follicle infundibulum, and sebaceous glands _Clinical presentations:_ – Dry form (seborrhea sicca) → dry skin and white-to-gray scales that exfoliate – Greasy form (seborrhea oleosa) →excessive brown to yellow lipids

Answer 115

Primary Idiopathic Seborrhea

Answer 116

• Types – Arctic breeds – inherited defect in zinc absorption – Rapidly growing large-breed dogs fed low zinc diet • Gross: scaling around mouth, chin, eyes, pressure points, pawpads

Answer 117

Fig. 17-70 Zinc-responsive dermatosis, skin, dog. A, Siberian husky. Periocular skin is thickened, alopecic, pigmented, and covered by tightly adherent scale. In Siberian huskies and Alaskan malamutes in particular, scaling and crusting develop in the skin around the mouth, chin, eyes, external ears, pressure points, and pawpads. B, Note the papillary epidermal hyperplasia (H) with marked parakeratosis (P). The parakeratotic hyperkeratosis and acanthosis form the thickened adherent scale. Although epidermal hyperplasia and parakeratosis are features of zinc-responsive dermatosis, they also occur in other conditions (such as superficial necrolytic dermatitis, chronic surface trauma, and nasal parakeratosis). Therefore breed, lesion distribution, and other features in the clinical history or clinical chemistry analysis are important in differential diagnosis. H&E stain.

Answer 118

Caused by Sarcoptes scabiei Highly contagious and zoonotic Pathogenesis: _burrow into stratum corneum_ ----\>intense pruritis through hypersensitivity mechanism----\>self trauma, chronic irritation----\>hyperkeratosis, lichenification, alopecia **Characteristic of a chronic dermatitis that ends in hyperkeratosis** **VERY ITCHY**

Answer 119

Normal wombat (above) Wombat with sarcotic mange (below) MDx: chronic dermatitis

Answer 120

MDx: chronic dermatitis

Answer 121

Sarcoptes mites burrowed beneath the stratum corneum, and associated hyperkeratosis.

Answer 122

Callus Raised, irregular patch of thickened skin developing from chronic friction, usually over pressure points Histo: epidermal hyperplasia May develop secondary pyoderma

Answer 123

Many skin tumors are not true neoplasms... They are other benign disorders of growth such as: – Nodular hyperplasia – Hamartoma–redundant disorganized tissue normally present at the site – Cysts

Answer 124

Follicular cyst

Answer 125

Nodular sebaceous hyperplasia

Answer 126

Collagenous hamartoma skin tags

Answer 127

How do we describe these changes? What can we do to determine the pathological process and cause? Something is being added to the epidermis... papules The pathological process is likely a disorder of growth or inflammatory Differential Diagnoses?? What can we do to determine the cause? _Cytology:_ • Low numbers of spindle cells, some mixed leukocytes. – Probably not a round cell tumor or carcinoma. What next? Excisional vs incisional biopsy? How big of margins? Histopathology or not? Surgical margin assessment? want 1 fasical plane under the tumor and about 1 cm for margins Culture?

Answer 128

Pathologist report: MDx: Grade II soft tissue sarcoma Comment: excision does not appear complete

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Very common in dogs Types-- cells that have several different possible origins that can not be distinguished pathologically – Fibrosarcoma – Nerve sheath tumor – Malignant fibrous histiocytoma – Liposarcoma – Myxosarcoma Have overlapping histological features and similar prognosis --\>treat the same Prognosis predicted by grade and margins **Locally invasive, slow to metastasize**

Answer 130

Caused by papilloma virus _Pathogenesis:_ viral genes inactivate host tumor-suppressor proteins Benign, spontaneously regress Gross: horny cauliflower-like masses

Answer 131

Fig. 17-45 Cutaneous papillomas, skin. C, The papillary projections (arrows), often called fronds, are composed of hyperkeratotic epidermis covering a collagenous core. H&E stain.

Answer 132

Very common in young adult horses **Thought to be caused by bovine papilloma virus** Frequently involve sites of previous wounds Invasive, high rate of recurrence, but do not metastasize Gross: variable range from nodular to plaque-like to wart-like **_Histo: composed of both epithelial and dermal components – need a biopsy that is not ulcerated to diagnose!_** Remember that it looks like proud flesh, so you have to do a biospy to tell the difference.

Answer 133

Equine Sarcoid

Answer 134

Pathogenesis: solar radiation, chronic injury commonly involved Gross: – Verrucous and ulcerated _– Poorly pigmented_,sparsely haired, sun-exposed areas Histo: keratinizing squamous cells gone wild

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Squamous cell carcinoma

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Bilateral squamous cell carcinoma in ear tips of sheep, site of chronic fly strike (R);

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Eyelid squamous cell carcinoma in a cow due to UV exposure.

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* Benign growth of dogs * Gross: – White-yellow , greasy, cauliflower- like

Answer 139

Sebaceous adenoma

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* Benign growth of dogs \>\>\> cats * Gross: – Looks and feels like fat,only forming a nodule • Histo: – Looks like normal fat

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Dog - behavior varies with grade but all considered potentially malignant Cats, horses - benign---- NO GRADING SYSTEM DEVELOPED! • Gross: – Can look like anything – Often resembles inflammation

Answer 142

Mast Cell Tumor

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Dogs, mostly **young**, but any age Head, ears, neck, distal forelegs Gross: dome-shaped Cyto: round cells Langerhans’ cell origin (epidermal dendritic antigen-presenting cell) **Benign, often spontaneously regress**

Answer 144

Histiocytoma

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Dog, horse, angora goat Gross: usually dark brown Histo: characteristic “junctional change” (in nonulcerated biopsies!) Location, size, mitotic index, and cell morphology may help predict behavior _– Canine:_ oral, mucocutaneous, subungual,- often malignant haired skin often benign _– Gray horses_ • usually progressive and multicentric WANT EPIDERMIS IN THE BX

Answer 146

Pathogenesis: solar radiation Hemorrages everywhere Young adult dogs • Hemangiosarcoma – Not as malignant as visceral counterparts – Primary to skin or metastatic from visceral tumor – Metastatic potential may vary with depth of tissue invasion these bleed a lot

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junctional change in melanomas

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Pathogenesis: solar radiation Young adult dogs • Hemangiosarcoma – Not as malignant as visceral counterparts – Primary to skin or metastatic from visceral tumor – Metastatic potential may vary with depth of tissue invasion

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Hemangioma

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Hemangiosarcoma.

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Many species, esp. dogs Poor prognosis * Epitheliotropic – T-cells * Nonepitheliotropic – T or B cells BAD PROGNOSIS

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Epitheliotropic

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CD3 (T-cell) immunohistochemistry

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Non-epitheliotropic

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Tips for differentiating - Look for color change - Melanin – darker color (added), lighter color (lost) - Calcium – chalky white, gritty to hard texture

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The pigment which imparts skin color Factors that influence production: – Hormones – Genes – Age – Inflammation

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tyrosainse requires copper

Answer 158

**_• Usually increase in amount of melanin rather than number of melanocytes_** • Generalized – Endocrine dermatosis (Cushing’s, Hypothyroidism, Hyperestrogenism) – **Acanthosis nigricans**– genetically determined disease of young dachshunds • Localized – Chronic inflammation or physical irritation (rubbing/friction) – Congenital (freckles)

Answer 159

Dog with Cushing’s disease (hyperadrenocorticism). MDx:cutaneoushyperpigmentation

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Dog with chronic flea allergy dermatitis. MDx: Chronic dermatitis and cutaneous hyperpigmentation. Regional------\> dermatitis

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Numbers can decrease or amount of melanin can decrease **_Congenital_** – Inherited lack of melanocytes – various conditions of horses, dogs, cats; associated with deafness – _Piebaldism_ – foci of lack of melanocytes – _Albinism_ – melanocytes are present but defect to synthesize melanin (usually tyrosinase gene); color dilution is a mild form **_Acquired_** – Copper deficiency – Destruction of melanocytes or melanin-containing keratinocytes (“pigmentary incontinence”) – scars, autoimmune dermatoses, vitiligo

Answer 162

MDx: Leukoderma. Dog with discoid lupus (below).

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MDx: Focal leukoderma/leukotrichia Horse acquired hypomelanosis (depigmentation) due to freeze branding Cow with acquired hypomelanosis (depigmentation) due to copper deficiency

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Horses with vitiligo, an idiopathic acquired melanocytopenic hypomelanosis (depigmentation). Gradually expanding pale macules, often symmetrical. Genetic inheritance. Pathogenesis of melanocyte death? not understood but genetic predisposition Micheal Jackson

Answer 165

The most common forms observed in the skin are both classified as dystrophic calcification, but pathogenesis not understood for both! _Calcinosis cutis_ – Associated with hyperadrenocorticism(Cushing's Disease) – Erythematous to white gritty plaques and nodules _Calcinosis circumscripta_ – Young, rapidly-growing, large-breed dogs – Single hard subcutaneous nodule, usually over pressure points or at previous site of trauma/injection

Answer 166

Fig. 17-66 Calcinosis cutis, **hyperadrenocorticism**( CUSHING"S DISEASE- PATHONUERMOTIC LESIONS) skin, dog. A, Dorsal neck. The skin is partially alopecic, ulcerated, and crusted. It is also palpably thickened. B, Subcutis. Mineral deposits are visible as white nodular foci.. chalky foci in the skin

Answer 167

Dog with **_calcinosis circumscripta._** Mild granulomatous inflammation surrounds deposits of calcium within the dermal and subcutaneous connective tissue. young, large bred dogs often over pressure points MDx: Cutaneous calcification

Answer 168

• Mucin is normally in the dermis (protein bound to hyaluronic acid) • Gross: – Thickened/puffy gelatinous skin – If severe can exude viscous fluid when pricked with needle – Prone to injury _Seen with:_ – Inherited mucinosis in the **_Chinese Shar-Pei_** – Myxedema with hypothyroidism When you squeeze out fluid, it's still a nodule(opposite of a papule)

Answer 169

Excessive mucin deposition (mucinosis) in the shar pei. MDx: cutaneous micinosis or cutaneous mucin

Answer 170

DERMATOPHILIUS