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Clinical Endocrine, Metabolic and Dermatology > Pathology: Dermatology 1 + 2 + 3 > Flashcards

Pathology: Dermatology 1 + 2 + 3 Flashcards

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1
Q

What are the main terms used in dermatology?

A
  • Vesicles/ Bulla
  • Pustules
  • Papule
  • Plaque
  • Ulcer
  • Epidermal collarette
  • Crust
  • Scale
  • Nodule
  • Lichenification
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2
Q

What is the following?

  • Palpable elevation filled with clear fluid
  • < 1 cm
A

Vesicle

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3
Q

What is the following?

  • Palpable elevation filled with clear fluid
  • > 1 cm
A

Bulla

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4
Q

What can cause a vesicle or bulla?

A
  • Auto-immune
  • Viruses
  • Chemical irritants
  • Burns
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5
Q

On histology, a subcorneal vesicle has formed, where the stratum corneum forms the roof, what type of pemphigus is this?

A
  • Pemphigus foliaceous
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6
Q

On histology, a suprabasal vesicle has formed, where the stratum spinosum forms the roof, what type of pemphigus is this?

A
  • Pemphigus vulgaris
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7
Q

On histology, a subepidermal vesicle has formed, where the entire epidermis separates from the dermis to form the roof, what type of pemphigus is this?

A
  • Bullous pemphigus/ pemphigoid
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8
Q

What is the following?

  • Palpable elevation filled with pus (leukocyte infiltration)
  • < 1 cm
A
  • Pustule
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9
Q

What is the following?

- dried exudate- serum, blood and scale that is adherent to the skin surface

A
  • Crust
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10
Q

What can cause a Crust to form?

A
  • Severe disorders of keratinization
  • Severe pustular dermatitis: where pustules rupture
  • Secondary to ulcers
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11
Q

What is the following?

- palpable, solid/ firm, elevated mass <1cm diameter

A

Papule

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12
Q

What can cause a Papule to form?

A
  • Infiltrate of inflammatory/ neoplastic cells
  • Epidermal hyperplasia
  • Deposit of mineral
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13
Q

What is the following?

- circular rim of scale secondary to the rupture of a vesicle, pustule, or papule

A
  • Epidermal collarette
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14
Q

What is the following?

  • solid, elevated flat-topped lesion formed from coalesced papules
  • > 1 cm
A
  • Plaque

Plaques are just papules that have coalesced together

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15
Q

What is the following?

- palpable, solid/ firm, elevated mass >1cm diameter and deeper in the dermis

A
  • Nodule
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16
Q

What is the following?

- loss of epidermis with the exposure of the dermis

A
  • Ulcer
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17
Q

What can cause an ulcer to form?

A
  • Epidermal necrosis
  • Inflammation
  • Infarction
  • Neoplasia
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18
Q

What is the following?

- thickening and hardening of the skin

A
  • Lichenification
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19
Q

What can cause lichenification of the skin?

A

Chronic irritation/ inflammation

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20
Q

What is the following?

- accumulation of loose keratinized cells = ‘dandruff’

A
  • Scales
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21
Q

What can cause Scales/ Dandruff to form?

A
  • Disorders of keratinization

- Chronic dermatitis

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22
Q

What are the 5 main groups of diseases that affect the epidermis?

A
  • Pustular diseases
  • Bullous diseases
  • Necrotizing diseases
  • Hyperplastic diseases
  • Diseases with abnormal cornification
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23
Q

Describe Pustular diseases of the Epidermis

A
  • Suppurative/ pustular/ exudative/ neutrophilic
  • Causes are usually bacterial infections, but can be due to autoimmune
  • If bacterial infection = Pyoderma, which is a name for a group of diseases: impetigo, intertrigo, hot spot, exudative epidermatitis, dermatophilosis
  • If autoimmune = Pemphigus foliaceous
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24
Q

Define Pyoderma

A

An encompassing term, used to describe several diseases: impetigo, intertrigo, hot spot, exudative epidermatitis, dermatophilosis

  • Literally means: Pus in the skin
  • Divided into 2 subtypes: superficial pyoderma and deep pyoderma
    • Superficial Pyoderma = involves the epidermis and hair follicles: canine superficial spreading pyoderma/ bacterial folliculitis, Impetigo (superficial pustular dermatitis), Intertrigo (skin fold dermatitis), Pyotraumatic Dermatitis (aka Hot spots), Exudative epidermatitis (Greasy pig disease), Dermatophilosis

– Deep Pyoderma = involves the deep dermis: bacterial furunculosis (rupture of the hair follicles) + abscess formation

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25
Q

What are the possible routes of entry that can cause Pyoderma?

A
  • Follicular openings
  • Hematogenous spread
  • Direct entry through damaged skin
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26
Q

What are the predisposing factors to developing Pyoderma?

A
  • Disorders of keratinization (seborrhea)
  • Endocrine disease
  • Chronic dermatitis: allergy vs parasite etc.
  • Immunodeficiency
  • Anatomic predisposition
  • Common in dogs, compared to cats: dogs have a thin stratum corneum, they lack the lipid seal of hair follicles and have a high skin pH
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27
Q

Describe Impetigo

A
  • This is a superficial pustular dermatitis
  • Caused by Staph intermedius, which releases exfoliative toxins that cause intra-epidermal splitting
  • Common in prepubescent and pubescent dogs
  • Associated with poor environmental hygiene or poor nutrition
  • If found in adults, look for an underlying immunosuppression
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28
Q

Describe Intertrigo

A
  • This is skin fold pyoderma
  • Commonly seen in brachycephalic breeds: skin folds of the face create frictional trauma and trap moisture, this allows for opportunistic bacterial infections +/- Malassezia
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29
Q

Describe Pyotraumatic Dermatitis (aka Hot Spots)

A
  • Moist, alopecia, slightly raised, red, well-circumscribed lesions leading to ulceration + crusting = very painful
  • Hot spots are very common in dogs, especially with long hair and dense undercoats, and more common in hot humid weather
  • Pathogenesis: self-trauma, leading to bacterial infection+/- underlying pruritus such as flea allergy dermatitis
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30
Q

Describe Pustular or Exudative Epidermatitis

A
  • Proper name for Greasy Pig Disease = etiological agent is Staph hyicus, but can be due to other Staph infections
  • This is a collection of small papules and pustules, which starts at the head and can become generalized in 24-48 hours
  • Smells bad, greasy exudate and is usually non-pruritic
  • Predisposing factors = other skin lesions, poor nutrition/ husbandry, lacerations from biting or sharp edges in the environment, wrong temp or humidity
  • Histopathology = Subcorneal pustules, neutrophilic exocytosis (neutrophils moving up through the epidermis), spongiosis (edema in the epidermis), intracellular edema
  • Can be fatal in neonatal pigs
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31
Q

Describe Dermatophilosis

A
  • aka Rain Rot/ Rain Scald
  • Etiological agent = dermatophilus congolensis, which is a gram + filamentous bacteria
  • Predisposing factors: wet weather in humid climates, leading to prolonged wetting of the skin/ hair/ wool, allowing penetration of the epidermis by zoospores
  • Histologically: pustule formation + bacteria
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32
Q

Describe Pemphigus foliaceous

A
  • An autoimmune disease involving antibody-mediated reactions against cell adhesion proteins (desmosomes)
  • Pemphigus foliaceous is the most common and mildest form of pemphigus, and is reported in dogs, cats, horses, and goats
  • Can be spontaneous, drug-induced or associated with allergic skin diseases
  • Usually affects the face, ears, footpads and clawbeds, which leads to a pustular dermatitis, involving vesicles, pustules, crusts, and ulcerative lesions
  • Histologically: will see eosinophilic pustular dermatitis with intralesional acantholytic keratinocytes and non-degenerative neutrophils
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33
Q

What are the 3 Bullous Diseases of the Epidermis?

A

1) Pemphigus vulgaris
2) Bullous Pemphigoid
3) Epidermolysis bullosa

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34
Q

Describe Pemphigus vulgaris

A
  • Very severe autoimmune disease affecting the deep layers of the skin, of the whole body, in particular areas of trauma (e.g. claw folds, underarms, groin and mouth)
  • Will see deep ulcers, itchy skin and pain, fever, lethargy, depression, anorexia
  • Can develop into bacterial infections which are common and fatal
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35
Q

Describe Bullous Pemphigoid

A
  • The most severe of the pemphigus diseases

- Will see deep ulcers, itchy skin and pain, fever, lethargy, depression, anorexia

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36
Q

Describe Epidermolysis bullosa

A
  • This is a mechanobullous or autoimmune disease Mechanobullous/ Hereditary form = congenital malformation of collagen
    Acquired/ Autoimmune form = Antibodies are produced against the collagen
  • In children, they are called the Butterfly children
  • Reported in Humans, dogs, cats and cattle
  • Histologically: will see loss of epithelial integrity, blister formation and sloughing of skin
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37
Q

What are the Necrotizing Diseases of the Epidermis?

A
  • Erythema multiforme + Toxic epidermal necrolysis
  • Superficial necrolytic dermatitis
  • Photosensitization
  • Herpesvirus
  • Cowpox virus
  • Burns
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38
Q

Describe Erythema multiforme + Toxic epidermal necrolysis

A
  • Toxic epidermal necrolysis is a more severe form of Erythema multiforme
  • They are both uncommon type 4 hypersensitivities towards antigens on the keratinocyte surface, which induces apoptosis
  • Cause: believed to be antigenic mimicry following drug administration, an underlying infection, neoplasia, dyes/ preservatives in pet foods
  • Will see widespread coalescing erythematous macules (target lesions), leading to vesicle formation and ulcers in the trunk, axilla and groin
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39
Q

Describe Superficial Necrolytic Dermatitis

A
  • Skin disease associated with liver disease = Hepatocutaneous syndrome. In cats, it can be associated with neoplasias in the liver or pancreas
  • Pathogenesis: liver disease leads to issues with the metabolism of proteins, these proteins are needed for collagen in the skin
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40
Q

Describe Photosensitization

A

UV light is absorbed by photodynamic chemicals in the skin, leading to free radical damage, and epidermal necrosis of lightly pigmented or sparsely haired skin

Type I (primary): ingested photodynamic substances, such as plants with photoreactive pigments, or mycotoxins, molds, chemicals and rugs (quinolones and griseofulvin)

Type II (intrinsic): endogenous pigment accumulation due to a defective porphyrin metabolism

Type III (Hepatogenous): abnormal build up of phylloerythrin due to liver disease or biliary obstruction (common in severe forms of liver fluke)

  • Histopathology (regardless of type): coagulative necrosis of epidermis, dermal edema, fibrinoid degeneration of vessel walls and thrombosis
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41
Q

Which herpesvirus types have a cutaneous predilection?

A
  • Bovine herpesvirus 2 (cattle): causes bovine ulcerative mammillitis, and pseudo-lumpy skin disease
  • Bovine herpesvirus 4 (cattle): causes bovine herpes mammary pustular dermatitis
  • Feline herpesvirus 1 (cats): feline facial dermatitis and stomatitis
  • Feline Cowpox virus (cats)
  • Ovine herpesvirus 2 (cattle): malignant catarrhal fever
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42
Q

Bovine herpesvirus 2 (cattle) is responsible for what disease(s)?

A
  • Ulcerative mammillitis: this is a self-limiting disease that affects the udder and teats
  • Pseudo-lumpy skin disease (PLSD): this is a generalized superficial skin disease, that leads to cutaneous nodules and plaques with central depressions (due to necrosis)
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43
Q

Ovine herpesvirus 2 (cattle) is responsible for what disease?

A
  • Malignant catarrhal fever
    These animals usually present with fever, depression, ocular and nasal discharge, lesions of the buccal cavity and muzzle, swelling of lymph nodes, an opacity of the corneas, inappetence and diarrhea
    Some animals, when the disease goes systemic and to the brain tissue, it can cause neurological signs like ataxia, nystagmus and head pressing
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44
Q

Feline herpesvirus 1 (cats) is responsible for what disease?

A
  • Feline herpesvirus ulcerative dermatosis
    Leading to upper respiratory tract disease such as rhinotracheitis and conjunctivitis
    Can get erosions and ulceration of the face (muzzle, periorbital regions and planum nasale)

Histologically: Severe necrosis and ulceration of the epidermis and dermis, massive exudation to form large superficial crusts, mixed dermal inflammation with numerous eosinophils, large amphophilic intranuclear inclusion bodies in the epithelium

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45
Q

Feline Cowpox Virus (cats) is responsible for what disease?

A
  • Ulcerating, red, crusted macules of the head, neck or forelegs. Believed to be from the bites of rodents, hence the areas that it appears
  • Is zoonotic
  • Histology: severe ulceration, serocellular crusting, ballooning degeneration of keratinocytes (epidermis and hair follicles) - numerous, large intracytoplasmic, brightly eosinophilic inclusions
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46
Q

Describe Solar Injury/ Sunburn

A
  • Acute severe UV light exposure leading to a sunburn
  • Gross: red, blistering/ vesicles and the sloughing of necrotic skin
  • Pathogenesis: direct cellular injury by ionizing radiation, leading to endothelial damage and cytokine production
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47
Q

What are the 4 Hyperplastic diseases of the Epidermis?

A
  • Chronic hyperplastic dermatosis
  • Acral lick dermatitis
  • Malassezia dermatitis
  • Pox virus/ parapox virus
48
Q

Describe Acral lick dermatitis

A

This is a self-inducing traumatic skin lesion, usually of the dorsal distal extremity

  • Cause: strong psychogenic component (boredom), but must rule out allergy, bacterial or fungal disease, demodicosis, previous trauma and underlying joint disease
  • Gross: alopecic, firm and oval plaque
  • Histology: compact hyperkeratosis, severe irregular acanthosis (epidermal hyperplasia) +/- erosion or focal to extensive ulceration with exudation, inflammatory cells perivascular, perifollicular, or diffuse and often perihidradenitis +/- deep folliculitis and furunculosis
49
Q

Describe Malassezia dermatitis

A
  • Very common in dogs
  • etiological agent: Malassezia pachydermatis, often secondary to another underlying disease (rarely it is a primary event, unless the dog has a hypersensitivity to Malassezia)
  • Leads to excessive sebum production, moisture accumulation and disruption of normal barrier function
  • Gross: Focal, multifocal, or generalized; ventral neck, ventral abdomen, axillae, face, pinnae, feet, forelegs, and skin folds: erythema, greasy or waxy adherent scales and crusts, hair loss, hyperpigmentation, lichenification, ‘musty’ odour.
50
Q

Parapox viruses are responsible for what diseases?

A
  • Bovine Papular Stomatitis
  • Orf (Contagious Ecthyma)
  • Parapox of red deer
  • Pseudocowpox
  • Sealpox
51
Q

Describe Orf (Contagious Ecthyma)

A
  • Parapox virus infection in sheep
  • Causes vesicular formation on the mucous membranes and teats of ewes
  • Is painful, common, contagious, zoonotic,
52
Q

What are the 6 Diseases that cause Abnormal cornification (too much keratin/ stratum corneum)?

A
  • Seborrhea (Seborrhea dermatitis, ear margin seborrhea)
  • Sebaceous adenitis
  • Nasodigital hyperkeratosis
  • Ichthyosis
  • Callus
  • Zinc responsive dermatosis
53
Q

Describe Seborrhea

A
  • This is a non-specific name for excessive scaling, crusting and greasiness
  • Primary vs Secondary causes
    • Secondary: due to underlying endocrinopathies or allergies, and is commonly associated with superficial pyoderma, Malassezia infections and alopecia

– Primary: Idiopathic or inherited cause. WHWT, Cocker Spaniels and Labs are most commonly affected

Primary Idiopathic Seborrhea:

    • Pathogenesis: thought to involve hyperproliferation of the epidermis, hair follicle infundibulum and sebaceous glands
    • Histology: marked epidermal and follicular hyperkeratosis + comedones

Primary Inheritied Seborrhea:
– Pathogenesis: Inherited faulty keratinization, will see at a young age

54
Q

Describe Canine Ear Margin Seborrhea

A
  • Commonly seen, affects the margins of the ears. Dachshunds are overrepresented
  • Cause: thought to be due to abnormality in cornification
  • Will see adherent keratinous deposits on both the lateral and medial margins of the pinna
55
Q

Describe Sebaceous Adenitis

A
  • This is a heritable autoimmune disease of Standard Poodles and Akitas, that causes inflammation and loss of sebaceous glands
  • Leads to scaling and poor quality coat
56
Q

Describe Nasodigital hyperkeratosis

A
  • This is an idiopathic, non-inflammatory disease of the planum nasale and pawpads
  • Doesn’t cause any real problems to the animal, more so aesthetically a problem
57
Q

Describe Ichthyosis

A

This is an inherited disease, where the animal is born with thickened and marked scaling of the skin (look like fish scales)

58
Q

Describe what a Callus is

A

This is a pressure point granuloma, commonly found on bony prominences or pressure points of giant or large breed dogs

59
Q

Describe Zinc Responsive Dermatosis

A
  • This is due to a dietary deficiency in Zinc, or excess zinc-chelators (calcium, iron or phytates)
  • Pigs: usually present at 2-4 months, and show anorexia and reduced growth rates
  • Ruminants: several in a herd will be affected, and show anorexia, weight loss, decreased milk production, depression and diarrhea
  • Dogs:
    • Syndrome 1: Siberian huskies, Alaskan malamutes <1 year of age
    • Syndrome 2: puppies of any breed
60
Q

What are the 4 diseases of the Dermis?

A
  • Perivascular and vascular dermatitis
  • Lichenoid dermatitis
  • Nodular/diffuse dermatitis
  • Degenerative, Dysplastic and Depositional Diseases
61
Q

Describe Perivascular and vascular dermatitis

A
  • Contains MANY diseases, but histologically it is non-specific

Perivascular dermatitis tends to be Hypersensitivity/ allergy or Parasitic related: resulting in inflammatory cells around vessels of the dermis +/- hyperplasia of the epidermis

Vascular Dermatitis tends to be more severe in nature

62
Q

What Hypersensitivity/ Allergy diseases can lead to Perivascular dermatitis?

A
  • Atopic dermatitis
  • Food allergy
  • Allergic contact dermatitis
  • Insect bite hypersensitivity
  • Feline allergic miliary dermatitis
  • Flea allergy dermatitis
  • Urticarial allergic eruptions (Urticaria or Hives)
63
Q

What Parasitic diseases can lead to Perivascular dermatitis?

A
  • Canine sarcoptic acariasis
  • Feline notoedric acariasis
  • Psoroptic mange
  • Chorioptic mange
  • Cheyletiellosis
64
Q

What are some potential causes of Vascular dermatitis?

A
  • Septic vasculitis
  • Immune-mediated vasculitis
  • Infarctions
  • Frostbite
65
Q

Define Atopy

Define Allergic Disease

A
  • Atopy is the tendency to produce an exaggerated IgE immune response (type I hypersensitivity) and degranulation of mast cells to otherwise harmless environmental substances
  • While an allergic disease can be defined as the clinical manifestation of this inappropriate IgE immune response

It is believed to be an inherited trait, although contact with the allergen or irritant must occur before the hypersensitivity reaction can develop

  • Potential allergens include: house dust mite proteins, plant pollen, mold spores etc.
66
Q

What are the clinical criteria for diagnosing Atopy in a patient?

A

The patient must have 3 of the 5 following:

1) Corticosteroid-sensitive pruritus
2) Erythema of the pinnae
3) Bilateral cranial erythematous pododermatitis
4) Cheilitis (inflammation of the lips)
5) Appearance of first signs between the ages of 6months and 3 years of age

Diagnosis of atopy is based on clinical signs, physical exam, intradermal skin testing, and the use of RAST (radioallergosorbent test) and the ELISA for elevated allergen-specific IgE

67
Q

Describe Atopy

A
  • Clinical signs include PRURITIS: of the face, paws, distal extremities, ventral abdomen
    • Skin lesions are due to self-trauma, secondary bacterial pyoderma, Malassezia dermatitis and secondary seborrhea
  • Gross: Alopecia, salivary staining of hair excoriations, papules, pustules, crusts, hyperpigmentation, lichenification, pyotraumatic dermatitis
  • Histology: Perivascular infiltrate of macrophages, lymphocytes, mast cells, few eosinophils and neutrophils
    Epidermis: erosions, hyperplasia, exocytosis of lymphocytes, eosinophils, subcorneal pustules
68
Q

In order to diagnose the offending allergen, and therefore cause of the atopy and the atopic dermatitis, you must carefully assess the _____ of the lesions

A

Location of the lesions!

  • Flea Allergy Dermatitis: dorsal lumbosacral area, groin and caudal thighs
  • Food allergy: the head and distal extremities
  • Allergic contact dermatitis: glabrous, exposed areas such the muzzle, groin, axillae, ventral interdigital webs and perineum.
  • Insect bite: Face, nose, eyes (mane and tail)
69
Q

Describe Urticarial Allergic Eruptions (Urticaria or Hives)

A
  • You get mast cell degranulation in response to IgE production
  • Histopathology: Dermal edema, mast cell degranulation, eosinophilic infiltration, capillary dilation
70
Q

Describe Sarcopic Mange

A

Parasite: Sarcoptes scabiei or Notoedres cati in cats

Dogs are affected at the ears, elbows, extend to ventral abdomen, face and legs

Complete life cycles in tunnels burrowed into and under stratum corneum = VERY ITCHY

+/- Allergic reaction: Acute/chronic perivascular dermatitis typical for allergic disease and continued scratching

71
Q

Describe Psoroptic Mange

A

Parasite: Psoroptes spp

  • Affects sheep (sheep scab) in the scrotum, testis, ears, inguinal and perianal folds
  • Affects cattle at the poll, ithers, base of tail
  • Affects horses in their ears
  • Affects Rabbits in their ears
  • Affects goats in their ears
  • Causes intense prurutis, leading to marked decrease in weight gain + reduced milk production
  • Histology: Superficial perivascular dermatitis with eosinophils, mast cells, lymphocytes, spongiosis, exudative, hyperplastic
72
Q

Describe Chorioptic Mange

A

Parasite: Chorioptes spp
– Most severe in winter, causing itching, erythema, alopecia, lichenification, wrinkling of skin

  • Affects cattle: perineum, tail, scrotum, udder and hindlimbs
  • Affects horses: lower limb and fetlock
  • Affects sheep: distal extremities
73
Q

Describe Cheyletiellosis

A

Parasite: Cheyletiella mite
– A zoonotic mite, causing mild itch

  • Affects dogs: mainly truncal scaling and mild crusting, lesions may be generalized in chronic cases. Itchiness is usually mild or absent
  • Affects cats: mild scaling and crusting, dorsal trunk but may be generalized, can see alopecia and poor haircoat. Itchiness is usually mild to absent
74
Q

Describe Septic Vasculitis

A
  • This is a rare secondary bacterial infection to sepsis
  • Caused by a severe deep pyoderma or a defect in the host immune response
  • Associated with bacterial endocarditis, with the release of septic emboli
  • Gross: Swelling, erythema, purpura, erythematous plaques, haemorrhagic bullae, necrosis, and ulceration: it can be generalized or localized (less extensive collateral circulation such as the distal extremities and pinnae)

Septic vasculitis always is life-threatening; can go into coma and death as possible sequelae.

  • Histology: neutrophils traveling through the walls, and causing damage to the vessel wall, leading to fibrinosuppurative or hemorrhagic exudation, vascular necrosis + fibrin thrombi, and leading to severe hemorrhage, edema and dermal necrosis
75
Q

Describe Immune-mediated Vasculitis

A
  • Reddened areas (hyperaemia/hemorrhage)
  • Edema development
  • Lesions follow a linear pattern and geometrical shapes (mapping to vascular supply)
  • Vascular lesions resulting in ischemia → then see features of degeneration/necrosis
  • Lesions can become inflamed secondarily to bacterial infections

e. g. Purpura hemorrhagic
- - Type III hypersensitivity, creation of antibodies that attack the proteins in endothelial cells (because they are similar to Strep. equi proteins)

76
Q

Describe Infarctions

A
  • Gross: Sharply demarcated geometrical shaped dark red to blue areas
    • Chronic: firm, dry, sunken, darkened (necrosis predominates over haemorrhage)
Causes:
- Vasculitis due to
Erysipelothrix rhusiopathiae 
Gram negative septicemias - Salmonella, Pasteurella, E. coli
Spider/snake bite
Drug reaction
Secondary to ulceration
  • Frost bite
  • Toxins causing extreme vasoconstriction (ergot)
77
Q

Describe Frostbite

A
  • Cause: exposure to cold temperatures
  • Pathogenesis:
    Formation of ice crystals which physically disrupt cells
    Vasoconstriction and endothelial damage →reduced blood flow →thrombosis →infarction
78
Q

Describe Lichenoid dermatitis

A
  • Dense superficial band-like or laminar dermal inflammation that is between the dermal-epidermal junction = interface dermatitis

Examples:

  • Mucocutaneous pyoderma
  • Discoid lupus erythematosus
  • Systemic lupus erythematosus

Histologically these diseases are difficult to differentiate and clinical correlation and response to treatment may be required for diagnosis.

79
Q

Describe Mucocutaneous pyoderma

A
  • Gross: Erythema, swelling, and adherent crusts around mucocutaneous junctions
  • Depigmentation of the lips
  • Pruritus is mild to moderate, and pain may be present
  • The pathogenesis is not understood. (bacterial infection maybe) - complex immunologic pathogenesis

Histology: Epidermal hyperplasia + exocytosis + spongiosis
Basal cell apoptosis, erosions, ulceration
Neutrophilic crusting
Dermis – perivascular to lichenoid infiltrates – predominantly plasma cells
Pigmentary incontinence (pigment present in the macrophages of the dermis)

80
Q

Describe Lupus Erythematosus (Discoid Lupus vs Systemic Lupus)

A
  • Autoimmune disease: Systemic Form vs Localized (Discoid) Form

– Systemic form (dogs, cats, horse)
T-cell imbalances, altered immune regulation
B-cell hyperactivity, production of auto-antibodies against a variety of membrane and soluble antigens (antinuclear antibodies)
Type III hypersensitivity reaction; Antibody-antigen complexes under basement membrane zone and in dermal vessel walls

UV light exacerbates
Breeds: Collies, German shepherds, Persian, Siamese cats
1/3 cases skin affected. Also polyarthritis, pyrexia, anaemia, glomerulonephritis
Mucocutaneous, ulcerative dermatitis on face, ears, nose, lips

– Discoid form (dogs)
Photosensitive nasal dermatitis
Nasal planum, perioral, periocular, pinnal skin
Collies, German shepherds
Gross: erythema, depigmentation, scaling crusting alopecia
Histology: Lichenoid/interface dermatitis with basal cell apoptosis

81
Q

What diseases can cause Nodular to Diffuse Dermatitis?

A
  • Actinomycosis
  • Mycobacteriosis
  • Acral lick dermatitis
  • Pseudomycetoma
  • Besnoitia and leishmania
  • Juvenile sterile granulomatous dermatitis and lymphadenitis
  • Foreign body reactions
  • Eosinophilic granuloma complex (feline and equine)
82
Q

Describe Actinomycosis

A

Pyogranulomatous osteomyelitis (lumpy jaw)
Can cause pyogranulomatous dermatitis (mycetoma)
Gram-positive bacterium Actinomyces bovis
Primarily cattle but can affect other species
Damage to the skin – crush, feeders etc
Gross: large nodular often ulcerated lesions
Histology: nodular to diffuse pyogranulomatous dermatitis with bacterial colonies surrounded by club-shaped brightly eosinophilic Splendore-Hoeppli material

83
Q

Describe Mycobacteriosis

A

Cats and dogs (cats more commonly affected)
Granulomatous mycobacterial skin diseases
Acid fast bacteria – hard to culture – PCR

Feline leprosy - Mycobacterium lepraemurium
Transmission unknown – biting insects?
FIV/debilitation may be predisposing factors
Numbers of mycobacteria in lesions can be low – might not see on histo

84
Q

Describe Juvenile sterile granulomatous dermatitis and lymphadenitis

A
  • aka Juvenile cellulitis, juvenile pyoderma, puppy strangles
  • Puppies (3 weeks to 6 months)
  • Dramatic response to immunosuppressive dosages of glucocorticoids →underlying immune dysfunction possible
  • Gross: acute swelling of the face, especially affecting the eyelids, lips, and muzzle. Lymphadenopathy. Bilaterally symmetric erythema, papules, nodules, and transient pustules and vesicles, usually within 24 hours.

+/- Secondary bacterial infections

  • Histology: granulomatous to pyogranulomatous inflammation within the dermis – nodules
    May extend to the panniculus and subcutis
85
Q

Describe Feline Eosinophilic Granuloma Complex

A
  • Not a disease, a pattern of lesions.
  • Tend to be pruritic

Several pathologies under one complex:
1) Indolent ulcer – ulcers on upper lips.

2) Eosinophilic plaque – discrete red to ulcerated plaques on the abdomen or medial thighs.
3) Eosinophilic granuloma – nodules (may be ulcerated) on thighs, face or mouth.

  • Commonly seen in cats with allergic skin disease.
  • Hypersensitivity pathogenesis suggested as they respond well to steroid treatment
  • Histology: Eosinophilic infiltration in dermis. Epidermal hyperplasia, spongiosis
86
Q

Describe Equine Eosinophilic Granuloma

A
  • Common nodular skin disease.
  • Single/multiple, firm circumscribed nodules.
  • Commonly on the Neck back and withers.
    Idiopathic.
  • Non-problematic unless they are around the areas of the saddle, where rubbing can be painful

Affects all ages breeds and both sexes.

Eosinophilic granuloma with central area of necrotic collagen and calcification

87
Q

What are the 4 Degenerative, Dysplastic and Depositional Diseases?

A
  • Calcinosis cutis
  • Calcinosis circumscripta
  • Ehlers Danlos syndrome
  • Feline acquired skin fragility
88
Q

Describe Calcinosis cutis

A
  • This is an inappropriate mineral deposition in the dermis, epidermis, or subcutis.
  • Commonly due to iatrogenic hyper-glucocorticism or Cushing’s Disease
  • Gross: Chalky, white-to-pink material with a feathery or blurry margin
    Firm, gritty yellowish-tan to dark red plaques evolve from coalescing erythematous papules.
    Ulceration and crusting occur as gritty mineral salts are extruded from older lesions (resemble sand)

-Most common in the flexural surfaces of the groin, back of the neck, and axillae.

  • Histology: Dystrophic mineralization of dermal collagen accompanied by granulomatous inflammation
    Occasionally osseous formation too
89
Q

Describe Calcinosis circumscripta

A
  • A clinically distinctive subgroup of calcinosis cutis, with focal deposition of mineral salts in tumour-like nodules, usually in the subcutaneous tissue
  • Causes include: Idiopathic or dystrophic
    Site predilection is prognostically important
    Tongue, ears (post cropping), bony prominences, injection sites, paws
  • In the paw pads, it usually indicates renal failure, especially if multiple paws are affected

Histology: granulomas centred on lakes of mineral – dermis and subcutis

90
Q

Describe Ehlers Danlos Syndrome

A
  • Cutaneous asthenia, dermatosparaxis
  • A Genetically and biochemically diverse disorder that encompasses multiple heritable, congenital defects of dermal connective tissue.
  • Histology: Collagen bundles irregular and haphazard arrangement
91
Q

Describe Feline Acquired Skin Fragility

A
  • Rare syndrome of multifactorial etiology
  • Skin is markedly fragile and thin skin, but without evidence of hyperextensibility
  • Minimal trauma leads to extensive tearing and shedding of the affected skin
  • Associated with iatrogenic and naturally occurring hyper-glucocorticism, diabetes mellitis, or the excessive progestational compounds
  • Less commonly associated with systemic diseases of the liver, kidney
  • Histology: Epidermal and dermal atrophy
92
Q

What are the diseases of the hair follicles and Adnexa?

A
  • Pustular and Nodular Diseases without Adnexal Destruction
  • Pustular and Nodular Diseases with Adnexal Destruction
  • Atrophic Diseases of the Adnexa
  • Diseases of the Panniculus
93
Q

What can cause Pustular and Nodular Disease without Adnexal Destruction?

A
  • Superficial bacterial folliculitis

- Dermatophytosis

94
Q

Describe Superficial bacterial folliculitis

A
  • Common in Dogs and cats
  • Etiological agent: Staphylococcus pseudointermedius
  • Usually secondary to coexistent disease or other predisposing factors
    +/- immunosuppression
  • Gross: follicular pustules →crusted papules.
    Alopecia, hyperpigmentation
    Inguinal and axilla, interdigital webs
  • Histology: Pustules within the infundibulum (folliculitis)
95
Q

Describe Dermatophytosis (Ringworm)

A
  • Superficial cutaneous, self-limiting
  • Caused by: Microsporum or Trichophyton

Common calves, horses, cats
Young animals or immunosuppressed

  • Fungi colonize keratin, do not need to invade tissue
  • Predisposing factors: Hot/humid environments
  • Zoonotic!

Gross: Expanding circular patches of scaling and alopecia or stubbled hair
Biopsy; to be taken within the expanding border

  • Fungal stains may be necessary
    PAS, Grocott

Histology: Neutrophilic luminal folliculitis +/- Furunculosis (hair follicle rupture)

96
Q

What are the causes of Pustular and Nodular Disease with Adnexal Destruction

A

Deep bacterial folliculitis and furunculosis:

  • Post-grooming furunculosis
  • Acral lick dermatitis
  • Interdigital furunculosis
  • Callus pyoderma
  • Canine acne

Feline acne
Canine demodicosis
Sebaceous adenitis

97
Q

Describe Deep bacterial folliculitis and furunculosis

A

Common – dogs and cats
Traumatic furunculosis include acral lick dermatitis, interdigital furunculosis, callus pyoderma, post-grooming furunculosis, and canine acne
Self inflicted – licking, rubbing, conformational, repeated trauma, severe back combing, back clipping or aggressive bathing
Furunculosis: traumatically released hair fragments and remnants of follicular keratin – foreign body reaction
Staphylococcus pseudointermedius, Proteus sp., Pseudomonas sp., and Escherichia coli

Predisposing factors: Generalized demodicosis, hyperadrenocorticism, widespread actinic disease and immunologic defects
Gross: Pustules, nodules, fistulas, haemorrhagic crusts, erosions, ulcers, alopecia, hyperpigmentation and lichenification
Dogs – haemorrhagic bullae
Pain and pruritus - self trauma
Histology: +/- ulceration, neutrophils within hair follicles, follicle rupture, pyogranulomatous inflammation around keratin and hair shaft fragments within the dermis

98
Q

Describe Feline Acne

A

Relatively common
Comedone formation and secondary inflammation on the chin and skin adjacent to the lips

  • Not associated with young age.
    Poor grooming habits and defects in follicular keratinization
    Staphylococcus spp., Streptococcus spp., and Pasteurella multocida
  • Histology: comedones, rupture, furuncluosis, granulomatous
99
Q

Describe Canine demodicosis

A

Noncontagious
Overpopulation of demodex species
Juvenile-onset and adult-onset forms
Localized (self limiting) or generalized (life threatening)
Familial - young dogs CMI defect
Adult-onset – often associated with systemic disease such as neoplasia, endocrinopathy, or immunosuppressive therapy

100
Q

What are the Atrophic Diseases of the Adnexa?

A
  • Hypothyroidism
  • Hyperglucocorticoidism
  • Hyperestrogenism
  • Post clipping alopecia
  • Feline psychogenic alopecia
101
Q

Describe Atrophic Dermatosis

A
  • This is a non-inflammatory disease of the hair follicle
  • Typically associated with endocrinopathies: Hypothyroidism, Hyperglucocorticoidism and Hyperestrogenism

Signs include:
Bilateral symmetric alopecia
Hyperpigmentation
Hair coat dry brittle, dull, easily epilated
Secondary pyoderma and seborrhoea are common

102
Q

What does Atrophic Dermatosis look like on histology?

A
  • Ortho-/ parakeratotic hyperkeratosis
  • Follicular keratosis
  • Decreased number of hair shafts in follicular infundibular
  • Mainly telogen hairs and follicular atrophy
  • Epidermal hypermelanosis
  • Dermal and sebaceous gland atrophy
103
Q

Describe Post Clipping Alopecia

A
  • This is a lack of hair regrowth following close clipping to the skin.
  • More common in plush coated breeds Siberian Husky, Alaskan Malamute, Samoyed, American Eskimo, Chow Chow, Keeshond, and Pomeranian

Cause unknown – think change in thermoregulation locally

Haircoat may not return for as long as 6 to 12 months after clipping
New coat may be darker

Histology: hairs in telogen phase (arrest stage)

104
Q

Describe Feline Psychogenic Alopecia

A
  • This is a self-traumatic hair removal
  • Associated with Obsessive/compulsive disorder or anxiety disorders
  • Diagnosis of exclusion
  • Well-demarcated, partial or almost complete alopecia over the lateral trunk, caudal and medial thighs, abdomen, and dorsal forelegs
  • Faeces – hair in excess
  • Histology: normal skin +/- mild inflammation
105
Q

What are the 5 diseases of the panniculus?

A
  • Vaccine-associated panniculitis
  • Traumatic panniculitis
  • Idiopathic sterile nodular panniculitis
  • Feline pansteatitis (rare) (vit E deficiency): most commonly reported cause is due to the feeding of red tuna as an exclusive diet or excessive cod liver oil supplementation
  • Pancreatic panniculitis (rare)
106
Q

General comments regarding Diseases of the panniculus

A
  • Commonly have a multifactorial etiology
  • Major focus of inflammation is in the fat of the subcutis
  • -> Lipocytes, fibrous trabeculae or septa, and blood vessels
  • -> Becomes a vicious circle, as inflammation of the lipocytes causes lipid release, which are pro-inflammatory, attract inflammatory cells and more lipocytes are damaged
  • Localized panniculitis is commonly initiated by local trauma or injection of foreign material: doesn’t have to be infectious
  • Generalized or multifocal panniculitis reflects metabolic or systemic disease; or remain idiopathic
107
Q

Describe Vaccine-associated panniculitis

A
  • Post-rabies – relatively common
  • -> can happen with any injection of any substance e.g. long-acting antibiotics
  • Gross: Focal alopecia – minimal gross inflammation, 2-3 months post vaccine

Cause: Unusual idiosyncratic immunological reaction to rabies antigen targeting blood vessels

  • Long-haired or curly-haired dogs overrepresented
  • Revaccination not recommended when this does happen
  • Histology: Ischemic lesions of the dermis (pale and atrophy). Accumulations of lymphocytes, fewer histiocytes, and occasional plasma cells - lower dermis and panniculus - surround vessels +/- amorphous basophilic foreign material
108
Q

Describe Traumatic Panniculitis

A
  • Focal ischemia caused by blunt trauma, chronic pressure, leading to a decreased blood supply
  • More common in obese cats and dogs
  • Gross: focal, firm subcutaneous nodule. Lesions are seen predominantly on the trunk, especially dorsally over the dorsal spinous processes, and over the sternum ventrally
  • -> Lesions are asymptomatic
  • Histology: large central focus of lobular fat necrosis. Ruptured adipocytes form large, cystic spaces. Foamy macrophages containing lipid debris. +/- hemorrhage or hemosiderosis. Marginal fibrosis.
109
Q

Describe Lupoid Onychitis

A
  • This is a canine syndrome
  • Affects the nails, where separation of the claw from the clawbed, sloughing of claws. Regrowth of misshapen, dry, brittle, short claws. Usually, all claws, all feet are affected.
  • Cause: Idiopathic, but adverse reaction to food and drug administration
  • Large breed dogs predisposed.
  • Histology: Interface (lichenoid) inflammation obscuring the junction between clawbed epithelium and adjacent dermis. Apoptosis and vacuolation of basal cells. Pigmentary incontinence.
110
Q

What type of primary cutaneous neoplasms can occur?

A 
- Epithelial neoplasms:
Epidermis 
Hair follicles
Sebaceous gland
Apocrine glands
Nail bed
  • Round cell:
    Histiocytic
    Mast cell
    Lymphocytic (lymphocytes and plasma cells)
- Mesenchymal neoplasms
Fibrous
Vascular
Perivascular
Lipocyte
Muscle
Neural
Melanocytic
Sarcoid
111
Q

What are the epithelial neoplasias?

Benign vs Malignant

A
  • Non-neoplastic or benign tumors:
    Dermoid cyst
    Papillomas
  • Malignant:
    Squamous cell carcinoma
    Basal cell carcinoma
112
Q

Describe a Dermoid Cyst

A
  • Occurs more in Dogs than cats
  • Cause: Developmental anomalies: focal reduplication of the entire skin structure, including dermis and adnexa
    Midline, solitary, dermal or subcutaneous nodule
    Small pore/ entry +/- hair
  • Occasionally extend into the spinal canal
  • Rhodesian Ridgeback are predisposed (can have single or multiple dermoid cysts)
113
Q

Describe a Papilloma

A
  • Caused by papilloma virus
  • 2 types of papillomas: Squamous and Fibropapilloma

Common in cattle, horses and dogs

  • Pathogenesis: viral genes inactivate host tumor-suppressor proteins
  • Benign, spontaneously regress, rarely progress to SCC
  • Gross: horny cauliflower-like masses
  • Histology: hyperplastic epidermis, supported by a thin dermal stalk with dilated capillaries. Marked expansion of the stratum spinosum and ballooning degeneration. Eosinophilic cytoplasmic inclusion that represents aggregates of keratin +/- viral inclusion bodies
114
Q

Describe a Squamous Cell Carcinoma

A

Common in cow, dog, cat, horse

Sites; often lack pigment, sparse hair

  • Horse, cattle; eyelid, penis
  • Cat; pinna, planum nasale, eyelids
  • Dog; head, abdomen, limbs and digits

Carcinogenic factors;
sunlight – UVB – free radicals
papilloma virus – not consistently identified
genetics

115
Q

What are the tumors of the sebaceous gland?

A
  • Benign: Nodular sebaceous hyperplasia
  • Benign: Sebaceous/ Meibomian adenoma / epithelioma
  • Malignant: Sebaceous carcinoma
  • Benign to Malignant: Perianal gland tumours – adenoma/ epithelioma/carcinoma
116
Q

Describe a Nodular Sebaceous Hyperplasia and Sebaceous Adenoma

A
  • These are common
  • Dogs > cats, older animals

Gross: yellow-white, alopecic, firm, and dome-shaped or papillated nodules that are less that 5mm in diameter (pigmented Meibomian glands)

Histology: multiple, enlarged, but otherwise normal sebaceous lobules
clustered around one or more dilated sebaceous ducts and hair follicles → hyperplasia
No orientation around ducts or follicles → adenoma

Epithelioma: increased basal reserve cells, increased recurrence, very rare metastasis

117
Q

Describe a Perianal (hepatoid) gland tumor

A
  • This is a nodular hyperplasia similar to sebaceous hyperplasia
  • Associated with androgens, and thus can see regression with castration (increase incidence in Entire Males)
  • Gross: Hyperplasia and adenoma – mm to 10cm +/- ulceration, rubbery, tan.
  • Histology: multiple enlarged lobules of well-differentiated hepatoid cells with a single peripheral layer of basaloid reserve cells
  • Perianal Carcinomas are rare, they tend to be more infiltrative, and metastasis is rare

Clinical Endocrine, Metabolic and Dermatology (17 decks)

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