derm path crusting

Question 1

Crusting skin diseases - what is crust? colours / types?histo term?

Answer 1

Crust is inflammatory exudate
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- A Crust is dried inflammatory exudate on the surface of the skin.
- Dark crusts are usually hemorrhagic.
- Yellow green crusts are typical of pyoderma
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- Histological term: SEROCELLULAR CRUST

Question 2

Crusting skin disease - how do they begin? types, and dermpath terms

Answer 2

◼ Exudate – fluid serum, edema - Vesicles
◼ Exudate plus cells - serocellular crusts
◼ Pustules of
> Neutrophils
> Eosinophils
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◼ VESICULAR and PUSTULAR DERMATITIS or VESICULOPUSTULAR DERMATITIS

Question 3

The Language of Skin: Vesicle and bulla definition / where they form, histo terms
- what to biopsy?

Answer 3

• A Vesicle can be formed within or just underneath the epidermis (pocket of inflammatory fluid)
• A Bulla is the same, only larger than 1cm
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  Histological term: VESICLE – SUBCORNEAL, SUPRABASALAR, SUBEPIDERMAL
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• vesicles will be found ruptured (forming ulcers) or intact > we want to biopsy the intact vesicle

Question 4

The Language of Skin:
Pustule definition, histo term

Answer 4

• A Pustule is a small circumscribed elevation of epidermis that is filled with pus. They are intraepidermal, subepidermal or follicular
  > filled with neutrophils or, sometimes, eosinophils
• Histological term: PUSTULE

Question 5

Crusting skin disease
- causes > infections vs non-infectious
- dermpath pattern

Answer 5

Infectious
◼ Bacterial disease (pyoderma)
◼ Fungal disease (dermatomycosis)
◼ Viral (herpesvirus, poxvirus, papillomavirus, picornavirus - FMD)
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Noninfectous
◼ Immune mediated disease (pemphigus foliaceous)
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DERMPATH pattern: VESICULOPUSTULAR DERMATITIS

Question 6

Defence mechanisms of skin

Answer 6

Immunological defence
◼ Innate
> Barrier function of skin
=> Keratin
=> Lipid
> Microbial pattern recognition
◼ Adaptive
> Skin immune system

Question 7

DERMPATH pattern: VESICULOPUSTULAR DERMATITIS
- mechanisms

Answer 7

Damage to keratinocyte
◼ Virus, bacteria
◼ Ballooning degeneration (cell swelling)
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Damage to intercellular bridges – desmosomes and hemidesmosomes and basement membrane zone.
◼ Neutrophilic enzymes (pyoderma, dermatophytosis)
◼ Antibody to desmoglein (humans), desmocolin (animals) (Pemphigus foliaceous)
◼ Spongiosis (intercellular edema of epidermis)

Question 8

VESICULOPUSTULAR DERMATITIS - subcategories, and their possible origins
- which is more common?

Answer 8

INTRAEPIDERMAL (very common)
◼ Bacterial (superficial) - pyoderma
◼ Fungal - Dermatophytosis
◼ Pemphigus diseases, especially - Pemphigus foliaceus
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SUBEPIDERMAL (Very rare)
◼ Congenital epidermolysis bullosa - (EB congenita)
> Aka epitheliogenesis imperfecta
◼ Acquired epidermolysis bullosa – ‘pemphigoid diseases’
> Autoimmune subepidermal blistering disease (AISBD) like Mucus membrane pemphigoid.