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Y3 - Skin pathology > Dermatopathology 1 > Flashcards

Dermatopathology 1 Flashcards

1
Q

Skin lesions can be classified based on which characteristics?

A
  • Underlying pathogenetic mechanism E.g. Vasculitis, immune-mediated disorder, inflammatory
  • Lesion type (pustules, bullae, folliculitis, etc…)
  • Distribution
  • Aetiological agents (not always clarified)
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2
Q

What are the 3 embryological layers of the skin?

A 
Outer = ectoderm 
Middle = mesoderm
Inner = endoderm
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3
Q

Describe the anatomy/structure of the skin and its components

A
  • Epidermis
  • Dermis, with collagen
  • Subcutaneous layer, made up of fat
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4
Q

90% of the cells in the skin are?

A

Keratinocytes

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5
Q

What other cells types are found in the skin?

A
  • Melanocytes
  • Hair follicles
  • Sebaceous glands
  • Apocrine glands
  • Cells with macrophagic function
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6
Q

What are the names of the 3 stages of the hair follicle cycle?

A

Anagen
Catagen
Telogen

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7
Q

Which part of the hair is the area of proliferation?

A

Papilla

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8
Q

Loss of keratinocyte cohesion is called?

A

Acantholysis

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9
Q

Define acanthosis?

A

Increased thickness of the stratum spinosum (often used to indicate epidermal hyperplasia)

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10
Q

Define alopecia?

A

Hair loss or failure to grow

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11
Q

Allergic skin disease is termed?

A

Atopy

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12
Q

Define bullae in the skin

A

Collection of fluid more than 1cm in diameter

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13
Q

Define folliculitis

A

Luminal, mural or perifollicular inflammation of the hair follicle

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14
Q

Define furunculosis

A

Perifollicular inflammation due to hair follicle wall rupture
- Dermal pyogranulomatous inflammation

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15
Q

Increased thickness of the keratin layer is termed?

A

Hyperkeratosis

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16
Q

What is a skin pustule?

A

Cavitation of the epidermis filled with inflammatory cells

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17
Q

Melanin granules and melanophages within the dermis is termed what?

A

Pigmentary incontinence

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18
Q

Define seborrhoea

A

Increased scale formation with or without excessive greasiness

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19
Q

Epidermal intercellular oedema is termed?

A

Spongiosis

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20
Q

A fluid filled blister of more than 1cm in diameter is called a?

A

Vesicle

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21
Q

What is Ki67 a marker of? (found in the nucleus of keratinocytes)

A

Indicates active cell division of the basal layer of the epidermis
- this is a normal finding on immunohistochemistry

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22
Q

What do black granules seen on immunohistochemistry represent?

A

Production of melanocytes

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23
Q

What is the function of melanocytes?

A

Repair and protect the nucleus of keratinocytes from UV light

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24
Q

What is the function of Langerhans cells?

A

Mononuclear
Dendritic
Antigen presenting cells of the epidermis

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25
Q

What are desmosomes?

A

Proteins that keep one cell (keratinocyte) attached to another

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26
Q

Basal keratinocytes are firmly adherent to the basal lamina via?

A

Hemidesmosomes

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27
Q

How would a pustule appear histologically?

A

As aggregates of neutrophils between keratinocytes on the surface of the epidermis

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28
Q

Name a vascular skin disease of pigs

A

Diamond skin disease

- venous infarct lesions of the skin

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29
Q

What are 3 causes of vasculitis?

A
  • Endotheliotropic organisms
  • Deposition of immune complexes
  • Septic emboli
30
Q

How does vasculitis appear grossly?

A
  • Haemorrhagic
  • Erythematous plaques, macules, purpura, oedema and ulcers
  • Chronic lesions: ulcers and dermal atrophy
  • Marked predilection for extremities (ear pinnae, lips and tail) – bits missing
31
Q

Define the following:

  1. Macule

2. Purpura

A
  1. a flat, distinct, discoloured area of skin

2. Purple discoloured coloured spots on the skin

32
Q

Describe the histological hallmark of vasculitis

A

Karyorrhectic cell debris (Leukocytoclastic) and fibrinoid necrosis of the vessel wall surrounded by fibrin exudation and haemorrhages

33
Q

Neutrophilic vasculitis is suggestive of?

A

A type III hypersensitivity reaction or septicaemia

34
Q

A cell mediated immune response causes which type of vasculitis?

A

Lymphoplasmacytic vasculitis

35
Q

Eosinophilic vasculitis is suggestive of?

A

A type I hypersensitivity reaction or other eosinophil-dominated dermatoses (e.g. eosinophilic granuloma)

36
Q

A superficial bacteria pyoderma is restricted to which part of the skin?

A

The dermis

37
Q

What is impetigo?

A

Superficial pustular dermatitis with no involvement of the hair follicle

38
Q

Describe the gross and histological features of impetigo

A

Gross: erythematous with papules that become pustules
Histo: subcorneal pustules composed of neutrophils

39
Q

What is the differential diagnosis for impetigo?

A

Pemphigus foliaceous

- no prominent acantholysis occurs in impetigo

40
Q

‘Greasy pig’ is called?

A

Exudative epidermitis of pigs

41
Q

Exudative epidermitis of pigs affects which age and is caused by?

A

Acute superficial exudative pyoderma of young (5-35 days) pigs caused by Staphylococcus hyicus

42
Q

What are the features of exudative epidermitis of pigs?

A
  • High morbidity and mortality

- Exotoxin produces cleavage between the stratum corneum and granulosum

43
Q

How does exudative epidermitis of pigs appear grossly?

A

Greasy dark brown exudate over eyes, snout, chin and ears which can spread over the body

44
Q

How does exudative epidermitis of pigs appear histologically?

A

Subcorneal pustular dermatitis

- epidermis covered with ortho- and parakeratotic hyperkeratosis, serum, neutrophils and bacterial colonies

45
Q

Describe the 3 clinical forms of exudative epidermitis of pigs?

A
  1. Acute - rapid spread to the whole body and death in 3-5 days
  2. Subacute - lesions confined to the head and high percentage of surviving piglets
  3. Chronic - High survival rate but poor growth
46
Q

Dermatophilosis is caused by which bacteria?

A

Dermatophilus congolensis

- Gram positive coccoid bacterium producing branching filaments

47
Q

What are the favourable conditions for Dermatophilus congolensis growth?

A

Skin trauma + a wet skin environment

48
Q

Describe the lesions caused by Dermatophilus congolensis?

A

Continuous and cyclic epidermal invasion, inflammation and regeneration causes thick parakeratotic crusts

49
Q

Which bacterial spp is most commonly involved in deep pyoderma?

A

Staphylococcus spp

50
Q

Describe the gross appearance and progression of lesions due to Staphylococcus spp (deep pyoderma)

A

Follicular papula -> pustule -> crust formation and coalescing ulcers and alopecia -> dark red nodules, ulcers and fistulae -> lymphadenopathy and fever -> epidermal acanthosis

51
Q

Describe the histological appearance and progression of Staphylococcus spp (deep pyoderma)

A 
Neutrophilic folliculitis (inflammation of the hair follicles) and furunculosis (inflammation caused by the disappearance of the hair follicle and the release of keratin) with bacterial colonies -> free keratin fragments (keratin scales) -> foreign body reaction and haemorrhages
- Suppurative inflammation with intracellular bacteria
52
Q

What are the entry routes of abscesses and cellulitis?

A

Contaminated wounds or contaminated foreign bodies

53
Q

What are abscesses and cellulitis associated with?

A

Fever and lymphadenopathy

54
Q

Define abscesses and cellulitis

A

Focal non-specific severe suppurative inflammations of the deep dermis and panniculum

55
Q

How does an abscess appear histologically?

A

Circumscribed central core of necrotic material and degenerate neutrophils surrounded by a granulation tissue-like reaction

56
Q

How does cellulitis appear histologically?

A

Poorly circumscribed extensive suppurative or pyogranulomatous inflammation with oedema, haemorrhage and thrombosis

57
Q

Cutaneous bacterial granulomas are caused by?

A
  • Actinomyces or Nocardia spp

- Mycobacteria infections e.g. M. tuberculosis and bovis

58
Q

A Cutaneous bacterial granulomas caused by Actinomyces or Nocardia spp has what gross features?

A
  • Pyogranulomatous dermatitis and panniculitis

- Grossly: large fibrotic and ulcerated nodules, often with draining fistulous tracts (sulphur granules)

59
Q

How do sulphur granules appear histologically?

A

Masses of basophilic to amphophilic organisms bordered by bright eosinophilic material

60
Q

Name 3 examples of viruses that affect the skin

A
  • Poxviruses
  • Herpes viruses
  • Papilloma viruses
61
Q

What is a poxvirus?

A

A DNA virus with high epitheliotropism that is responsible for numerous primary skin diseases

62
Q

Name some examples of poxviruses

A
  • Cowpox virus
  • Bovine papular stomatitis
  • Orf virus
63
Q

Poxviruses are capable of causing which 2 lesion types?

A

Vesicular and proliferative lesions

64
Q

How are the gross lesions of cowpox distributed and how do they appear?

A
  • Single distribution with predilection for face and forepaws
  • Ulcers -> papules and pustules in secondary lesions
65
Q

Describe how coxpox appear histologically

A
  • Focal sharply demarcated ulcer covered in fibrinonecrotic exudate
  • Large eosinophilic intracytoplasmic inclusion bodies in epidermal and follicular epithelia
66
Q

Describe the Features of Orf

A
  • Contagious pustular dermatitis
  • High morbidity, low mortality
  • Predominantly affects lambs and kids
67
Q

How are the gross lesions of Orf distributed and how do they appear?

A
  • Distribution: starting from lip commissure -> lips and muzzle -> legs (rare)
  • Appearance: Multifocal to coalescing raised and flat grey crusts
68
Q

How does Orf appear histologically?

A

Ballooning degeneration and spongiosis with prominent epidermal hyperplasia and crust formation

69
Q

Herpes virus dermatitis is caused by which virus in cats?

A

Feline herpes virus type 1

70
Q

How are the gross lesions of herpes virus dermatitis distributed and how do they appear?

A

Distribution: Primarily on nasal planum and haired skin of the face
Appearance: Persistent and recurrent crusts, ulcers and vesicles

71
Q

How does herpes virus dermatitis appear histologically?

A

Ulcerative and necrotising dermatitis, large intranuclear glassy inclusion bodies and mixed dermal infiltration

Y3 - Skin pathology (4 decks)

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