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Dermatology 2 Flashcards

Diagnostic sampling, cutaneous reaction patterns, approach to pustules, papules, scale and crust

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1
Q

Outline some special considerations for diagnostic sampling of cutaneous masses

A
  • May not be homogenous esp. if large, incisional wedge or excisional more representative vs punch
  • Incisional first if suspect invasive neoplasm
  • Ensure biopsy tracts are excised with adequate margins when tumour removed
  • Remove deeper tissue “en bloc” and submit untrimmed to look for spread
  • Max. 1cm tissue thickness for adequate fixation
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2
Q

Outline some special considerations for bacterial and fungal tissue culture

A
  • Tissue culture more valuable for superficial/deep pyoderma or deep fungal culture vs surface swabs
  • Withdraw antibiotics for 5-7 days before sampling for bacterial culture
  • Submit punch biopsy sample in sterile saline or sterile saline soaked swab , formalin toxic to bacteria
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3
Q

Describe the method for using a Wood’s lamp

A
  • Only M. canis will fluoresce
  • Pre-heat lamp for 5 mins before use, illuminate area of interest in darkened room
  • False positives an occur with certain drugs, soaps and bacteria (e.g. Pseudomonas), but these are not associated with hair shafts
  • False negatives common
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4
Q

What is the indication for use of a skin biopsy?

A

To establish a definitive diagnosis that cannot be reached by other, less invasive testing methods, in order to identify or rule out certain conditions

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5
Q

Give examples of key reasons for poor results on skin biopsy

A
  • Samples submitted not representative of lesion
  • Primary lesion obscured by secondary lesion
  • sample timing inappropriate
  • Sample examined not representative of lesion
  • Lesion destroyed by sampling
  • Unrealistic expectations of biopsy
  • Inadequate information given to pathologist
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6
Q

Outline the requirements for attaining good results on skin biopsy

A
  • Be gently
  • Biopsy early
  • Collect multiple samples representative of range of lesions
  • Include crusts
  • Biopsy before anti-inflamm. therapy
  • Label samples from different areas
  • Submit complete history, signalment, description, list of differentials and a diagram
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7
Q

How can the the response pattern to injury be used?

A
  • To formulate list of specific aetiological agents that could cause the lesion
  • To suggest categories of disease with similar lesions and common pathogenesis
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8
Q

What is actinic damage?

A

UV damage

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9
Q

Explain the main disadvantage of pattern analysis of a skin biopsy

A
  • Skin has a limited range of responses, so different disorders may have similar histological appearance
  • Diagnosis requires additional information incl. clinical lesion distribution, appearance, duration, location, past medication, other clinical data
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10
Q

Name the 8 patterns that dermatopathologists look for in a skin biopsy

A
  • Folliculitis/furunculosis/sebaceous adenitis
  • Perivascular dermatitis
  • Vasculitis
  • Nodular and/or diffuse
  • Interface dermatitis
    dermatitis
  • Intraepidermal/subepidermal Vesicular/pustular dermatitis
  • Panniculitis
  • Atrophic dermatoses
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11
Q

What is meant by hydropic degeneration?

A

Vacuoles in stratum basale leading to intrabasal or subepidermal clefts

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12
Q

Describe intracellular oedema

A

Occurs with hydropic degeneration of basal cells and ballooning degeneration. Seen with herpes virus infections

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13
Q

What is necrolysis?

A

Epidermal necrosis with no dermal involvement and minimal inflammation

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14
Q

Compare ortho and parakeratosis

A
  • Both are excessive cornification
  • In ortho, keratinocytes lose nuclei
  • IN para, keratinocytes retain nuclei
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15
Q

What is pigment incontinence?

A

Release of melanin granules into superficial dermis

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16
Q

What is spongiosis?

A

Intercellular oedema in the epidermis

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17
Q

What is dyskeratosis?

A

Abnormal, premature or imperfect keratinisation of keratinocytes

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18
Q

What is epidermolysis?

A

Degeneration of epidermal basal layer, leading to separation of epidermis from dermis

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19
Q

What hair follicle structures can be affected by inflammation? Give the name of this type of inflammation

A
  • Perifollicular vascular plexus = perifolliculitis
  • Follicular wall = mural folliculitis
  • Lumen of hair follicle = luminal folliculitis
  • Bulb = bulbitis
  • Sebaceous glands = sebaceous adenitis
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20
Q

Give examples of diseases that may lead to mural folliculitis

A
  • Pemphigus foliaceous

- Demodicosis

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21
Q

Give examples of disease that may lead to luminal folliculitis

A
  • Demodex

- Dermatophytes

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22
Q

In what condition does bulbitis of the hair follicle occur?

A

Alopecia areata

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23
Q

What is furunculosis?

A

Perforating folliculitis with release of keratin into dermis, setting up a marked inflammatory response

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24
Q

Describe the histological appearance of perivascular dermatitis

A
  • Prominent blood vessels
  • Oedema of dermis
  • Leukocytes around vessels
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25
Q

How is perivascular dermatitis classified, and give the names of the classes

A
  • Classified according to depth
  • Superficial dermal
  • Mid-dermal/perifollicular
  • Deep dermal
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26
Q

What types of cellular infiltrate may occur in perivascular dermatitis and what does each indicate?

A
  • Neutrophil: acute pyoderma
  • Lymphocytes: canine atopy
  • Eosinophil: type I hypersensitivity, parasitic? Allergic?
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27
Q

Describe the appearance of interface dermatitis

A
  • Cell rich OR cell poor band-like mononuclear infiltrate crossing the dermo-epidermal function (exocytosis)
  • Hydropic degeneration of basal keratinocytes
  • +/- apoptosis of individual cells, mainly in basal layer (diffusely attacked by lymphocytes or apoptosis induced)
  • Pigment incontinent
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28
Q

What is the importance of interface dermatitis?

A

More specific but more serious pattern compared to perivascular dermatitis, associated with immune mediated disease

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29
Q

Give examples of diseases that would cause an interface dermatitis pattern

A
  • Dermatomyositis
  • Erythema multiforme
  • Lupoid dermatoses
  • VKH (Vogt-Koyanagi-Harada)
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30
Q

What is the most common dermatological diagnostic pattern?

A

Perivascular dermatitis, but also least specific

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31
Q

Describe vasculitis diagnostic pattern

A
  • Inflammation of blood vessels
  • Tight perivascular cuffs of inflammatory cells with degeneration of vascular wall
  • Microhaemorrhages
  • +/-: panniculitis, dermal necrosis (disturbed blood flow to skin), atrophy of hair follicles
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32
Q

Give examples of diseases that may lead to vasculitits

A
  • Dermatomyositis
  • Rabies-vaccine induced panniculitis in dogs
  • Pastern dermatitis in horses
  • Classical swine fever
  • Malignant catarrhal fever
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33
Q

Briefly explain how a post-vaccination vasculitis can develop

A
  • Arthus reaction to vaccination
  • Rare, massive accumulation of Ag-Ab complexes depositing in vascular wall, leading to complement activation
  • Get alopecic macules
  • Type 3 hypersensitivity
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34
Q

How may a diffuse dermatitis pattern occur?

A

Convergence of nodules, progressive disease

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35
Q

List the cell types that may be present n nodular/diffuse dermatitis and give their aetiologic agent (5)

A
  • Neutrophils: pyogenic agents
  • Histiocytes/macrophages: foregin bodies, mycobacteria
  • Neutrophils + macrophages: furunculosis, fungi
  • Eosinophilic: parasitic
  • Lymphocytic: insect bites, vaccine reactions
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36
Q

What are potential underlying causes of vesicles or pustules? (intraepidedermal vesciular/pustular dermatitis pattern)

A
  • Oedema e.g insect bite with acute inflammation
  • Intracellular inflammation e.g. blister
  • Autoimmune disease attacking desmosomes
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37
Q

Explain the mechanism of vesicle or pustule formation (intraepidedermal vesciular/pustular dermatitis pattern)

A
  • Clefting in the epidermis
  • Spongiosis: intercellular pedema in epidermis, epidermal inflammation, parasites, infection
  • Acantholysis: infection, autoimmune disease
  • Intracellular oedema: mechanism forces
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38
Q

Compare the fluid found in vesicles and pustules

A
  • Vesicular is normal fluid

- Pustular is neutrophilic fluid

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39
Q

How can intraepidermal vesicular/pustular dermatitis be classified?

A

By position and cellular infiltrate

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40
Q

Describe the positional classifications of intraepidermal vesicular/pustular dermatitis

A
  • Subcorneal: very superficial, e.g. pemphigus foliaceous, pyoderma
  • Suprabasilar: deeper, e.g. pemphigus vulgaris
  • In follicular external root sheath e.g. pemphigus foliaceous
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41
Q

Describe the classifications of intraepidermal vesicular/pustular dermatitis based on cellular infiltrate

A
  • Neutrophils: bacterial pyoderma, pemphigu foliaceous

- Eosinophils: pemphigus foliaceous, parasitis

42
Q

Describe the histological appearance of oedema in the skin of a dog

A
  • Intercellular epidermal oedema
  • Increased spaced between keratinocytes
  • Spines between keratinocytes of stratum spinosum caused by widening of intercellular spaces by oedema
  • Remain attached via desmosomal attachment sites
43
Q

Compare the appearance of pemphigus vulgaris and foliaceous and explain why this difference occurs

A
  • PV characterised by large, confluent ulcers
  • PF characterised by erosions and crusts
  • Is because acantholysis in PV occurs deeper in epidermis
44
Q

Compare the prevalence of supepidermal and intraepidermal vesicular/pustular dermatitis

A

Supepidermal less common

45
Q

What may cause supepidermal vesicular/pustular dermatitis?

A
  • Autoimmune disease e.g. bullous pemphigoid
  • thermal burns
  • Severe dermal oedema
  • severe interface dermatitis
  • May be an artefact
46
Q

Describe the appearance of subepidermal vesicular/pustular dermatitis

A

Entire separation of epidermis from dermis

47
Q

Describe the difficulties associated with subepidermal vesicular/pustular dermatitis

A
  • Difficult to treat and prevent infection of totally exposed dermis
  • Loss of fluid
48
Q

What is panniculitis?

A

Inflammation of subcutaneous adipose tissue

49
Q

Give potential underlying causes of panniculitis

A
  • Extension of follicular disease
  • Infectious agents
  • Vasculitis
  • Foreign body
  • Pancreatic disease
  • Pancreatic carcinomas
  • Vitamin E deficiency
  • Trauma
50
Q

What is the most common cause of panniculitis and what does this mean for treatment?

A
  • Often sterile idiopathic, so treat with corticosteroids

- But need to eliminate possibility of infection before use of corticosteroids

51
Q

What are the potential outcomes of panniculitis?

A
  • Can extend into tissues
  • Pain
  • Subcut fat can be almost liquefied in severe panniculitis e.g. with pancreatic disease (due to lipases)
52
Q

What is meant by atrophic dermatosis?

A

Skin response pattern consisting of atrophy of epidermis, hair follicles, collagen and sebaceous glands. Is not inflammatory, is loss of skin structure due to atrophy.

53
Q

Describe the histological appearance of atrophic dermatosis

A
  • Orthokeratotic hyperkeratosis
  • Follicular keratosis
  • +/- calcinosis cutis if HAC
54
Q

What are the potential causes of atrophic dermatosis?

A
  • Various endocrine causes, require hormone assays to diagnose e.g. HAC, hypothyroidism
  • Any chronic systemic disease or malnutrition etc.
  • Not inflammation
55
Q

What are the 3 forms of eosinophilic granuloma complex?

A
  • Eosinophilic granuloma
  • Eosinophili plaque
  • Indolent ulcer
56
Q

Where do eosinophilic granulomas usually occur?

A
  • Caudal thighs
  • Oral cavity
  • Feet
  • Can be anywhere
  • Occasionally “fat chin”
57
Q

Describe the appearance of an eosinophilic granuloma

A
  • Well demarcateed, solid, raised, erythematous plaques/nodules
  • Eroded or ulcerated surface
  • +/- exudation, crust
58
Q

What are the differentials for an eosinophilic granuloma?

A
  • Neoplasia (SCC, lymphoma, MCT)
  • Dermatophytosis
  • Feline cowpox
  • Cutaneous viral disease
  • Mycobacterial infection
  • Deep fungal infection
  • Bacterial folliculitis, furunculosis, abscess
  • Foreign body reaction
  • Sterile granulomatous disease
59
Q

Describe the appearance of an eosinophilic plaque

A
  • Raised, flat topped erythematous plaque

- Usually pruritis

60
Q

Where do eosinophilic plaques usually occur?

A

Ventral abdomen, caudal thigh

61
Q

What are the differentials for eosinophilic plaques?

A
  • Neoplasia (SCC, lymphoma, MCT, metastatic mammary adenocarcinoma)
  • Dermatophytosis
  • Feline cowpox
  • Cutaneous viral disease
  • Mycobacterial infection
  • Deep fungal infection
62
Q

Where do indolent ulcers occur?

A
  • Aka rodent ulcers

- Mucocutaneous junction of upper lips

63
Q

Describe the appearance of indolent ulcers

A
  • Erosive/ulcerative lesion
  • Uni or bilateral
  • Rarey painful or pruritic
  • Possibly associated with pyoderma and a foreign body reaction to intradermal keratin caused by licking
64
Q

What are the differentials for an indolent ulcer?

A
  • Neoplasia (SCC)

- Trauma

65
Q

Discuss the role of cytology in the diagnosis of eosinophilic granuloma complexes

A
  • Helpful, esp. re differentiation from neoplasm
  • BUT absence of eosinophils does not preclude EGC
  • Also, eosinophils may be present with other diseases (mosquito bite hypersensitivity, FHV-1 dermatitis, mast cell tumour)
66
Q

What are the most likely underlying causes for EGCs?

A
  • Ectoparasites
  • Allergies
  • Recent information re. pyoderma
67
Q

Describe the diagnostic approach to eosinophilic granuloma complexes

A
  • Confirm EGC lesion with history, clin. exam, cytology and histopathology
  • Investigate underlying cause
68
Q

Describe the main histological features of an EGC

A
  • Varying degrees of epidermal hyperplasia and ulceration/erosion
  • Prominent eosinophilic dermal infiltrate
  • Small foci (flame figures) in which collagen fibres are surrounded by degranulation eosinophils seen in all 3 types of EGC
69
Q

List the treatment options for EGC

A
  • Ciclosporin
  • Glucocorticoids
  • Hydrocortisone aceponate
  • Chlorambucil
  • Interferon omega
  • Immunotherapy
70
Q

What need to be done before commencing treatment with ciclosporin for an EGC?

A

Test for FIV, FeLV and toxoplasmosis and discuss high cost with owner

71
Q

Outline the most common treatment for EGCs

A
  • Glucocorticoids e.g. prednisolone

- Often down to low dose every other day

72
Q

Discuss the use of chlorambucil in the treatment of EGCs

A
  • Not licensed in animals but consider in EGC cases that are refractory to steroid therapy
  • Can be given with steroids
  • Side effects infrequent, but monitor every 2 weeks on haematology
73
Q

Discuss the use of interferon omega in the treatment of EGCs

A
  • No clinical trials but has been suggested

- Should not be a first line treatment

74
Q

Discuss the use of immunotherapy in the treatment of EGC

A
  • Expensive
  • Owner trained to inject immunomodulating drugs every 2-4 weeks
  • Must be imported for needs an SIC
75
Q

Describe a papule

A
  • Small solid elevation of skin <1cm diameter
  • Often erythematous
  • My form cruss of serum, pus or blood (papulocrustous lesions)
  • Primary lesion
76
Q

Describe a pustule

A
  • Small <1cm skin elevation filled with pus, often starts as papule
  • Primary lesion
  • Colour varies: white, yellow, green, red (haemorrhagic)
77
Q

Where might pustules be located in the skin?

A
  • Intraepidermal
  • Subepidermal
  • Follicular
78
Q

What would the presence of many pustules indicate and why?

A

Deeper lesions as these are less fragile

79
Q

Describe the appearance of ruptured pustules

A
  • Epidermal collarettes

- Crusts adhered to skin

80
Q

What is scale?

A

Rafts of immature keratinocytes which accumulate at the skin surface

81
Q

What are crusts?

A

Exudates dried onto the skin

82
Q

What would bilaterally symmetrical crusts/scale with pinnal involvement be suggestive of?

A

Autoimmune disease

83
Q

List the skin diseases causing pustular/papular diseases in dogs, give the most common3 first

A

1: Superficial bacterial pyoderma
2: Ectoparasites
3: Hypersensitivities
- Fungal infections
- Insect bite reactions
- Autoimmune disorders
- Uncommon disorders

84
Q

Describe the clinical presentation of superficial bacterial pyoderma causing pustular/papular disease in dogs

A
  • Impetigo
  • Folliculitis
  • Acne
85
Q

Give the clinical presentation of ectoparasites that may cause pustular/papular disease in dogs

A
  • Flea bites
  • Sarcoptes
  • Demodex
86
Q

Give the clinical presentation of hypersensitivities that may cause pustular/papular disease in dogs

A
  • Flea
  • environmental atopy
  • Food induced atopy
  • contact
87
Q

Which fungal infections may cause pustular/papular disease in dogs?

A

Dermatophyosis, Malassezia

88
Q

Give the clinical presentation of insect bite reaction that gives pustular/papular disease in dogs?

A

Usually mosquito, usually acute (seasonal)

89
Q

Give the clinical presentations of autoimmune disorders that may cause pustular/papular disease in dogs

A
  • Pemphigus complex (sterile pustules)

- Bullous pemphigoid

90
Q

give the clinical presentations of uncommon disorders that may cause pustular/papular diseases in dogs

A
  • Drug eruptions
  • Juvenile cellulitis
  • Leishmaniasis
  • irritant reactions
  • Subcorneal pustular dermatitis
  • Sterile eosinophilic pustular dermatitis
91
Q

List the skin diseases that may cause pustular/papular disease in cats, and number the most common

A

1: Miliary dermatitis
2: Dermatophytosis
- Parasitic
- Superficial bacterial pyoderma
- Allergic
- Autoimmune
- Neoplasia

92
Q

Describe the clinical presentation of miliary dermatitis in pustular/papular skin disease in cats

A

Focal/diffuse small erythematous crusted lesions

93
Q

Describe the clinical presentation of dermatophytosis in pustular/papular disease in cats

A

Folliculitis, miliary-dermatitis type lesions

94
Q

Describe the clinical presentation of superficial bacterial pyoderma in pustular/papular disease of cats

A
  • Chin acne
  • Folliculitis
  • Impetigo
95
Q

Describe the clinical presentation of allergic skin disease in pustular/papular disease in cats

A
  • Flea
  • Atopy
  • Adverse food reaction
96
Q

Describe the clinical presentation of autoimmune disease in pustular/papular disease in cats

A

Pemphigus complex, esp. pinnae and around teats

97
Q

Describe the clinical presentation of neoplasia in pustular/papular disease in cats

A
  • Mast cell tumours

- Cutaneous lymphoma

98
Q

List the causes of miliary dermatitis in cats

A
  • Parasitic
  • Allergic
  • microbial
  • Miscellaneous
  • Systmemic disease
99
Q

Which systemic diseases may cause miliary dermatitis in cats?

A

FeLV infection, FIV infection, hyperthyroidism

100
Q

List the “miscellaneous” i.e. not parasitic, allergic, microbial, systemic diseases that can cause miliary dermatitis in cats

A
  • Nutritional deficiencies(EFAs, biotin, generic diet)
  • Epitheliotropic lymphoma
  • Pemphigus
  • Endoparasites (rare)
  • Idiopathic

Dermatology 2 (23 decks)

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