Dermpath pruritus Flashcards
Inflammatory skin disease (Dermatitis) - what are they called?
- aretiole
- subcutaneous fat
- hair follicle
- dermis
- Arteriole – vasculitis
- Subcutaneous fat – panniculitis
- Hair follicle – luminal and mural folliculitis and sebaceous adenitis
- Dermis – nodular to diffuse dermatitis
Inflammatory skin disease (Dermatitis) - terminology for:
5. Dermal capillaries and post capillary venules
6. Desmosomes
7. Hemidesmosomes
8. Keratinocyte
- Dermal capillaries and post capillary venules – perivascular dermatitis
- Desmosomes – intraepidermal vesicular and pustular dermatitis
- Hemidesmosomes – subepidermal vesicular and pustular dermatitis
- Keratinocyte – cytotoxic interface dermatitis
- Pruritic skin disease: Itchy dog or cat
- Clinical Dermatology: Pruritus
> corresponding common DERMPATH pattern
- Clinical Dermatology: Pruritus
- Common DERMPATH pattern – Perivascular dermatitis
Pruritic skin disease
- how common?
- do they need treatment?
◼ 85% of dermatology
◼ There are many causes
◼ Majority require clinical elimination
> No tests available
Neural pathways in pruritus
◼ Detector system – intraepidermal nerve fibre
◼ Sensory nerve
◼ Central center (ganglia, spinal cord and brain).
◼ Motor nerve
◼ Muscle of skeletal and digestive systems (mouth!)
> e.g. Scratch, rub, chew, lick
Pathogenesis of Pruritus - most cases involve what components?
The majority of cases involve
* Sensory detector system
* Sensory nerve or central center
Sensory detector system for pruritus - nerve components, what stimulates them?
C fibre nerves (unmyelinated) extend into epidermis
◼ Called intraepidermal nerve fibres (IENF)
> More IENF in dogs with atopic dermatitis than normal dog skin
<><><><>
Stimulation of IENF causes pruritus
◼ Directly
◼ Chemical mediators
◼ Keratinocyte products (cytokines!)
- Sensory detector system pruritus
- non-inflammatory vs inflammatory causes
Direct stimulation of IENF (noninflammatory)
◼ Dry skin – low humidity - Xerosis
◼ Intraepidermal lymphocytes (epitheliotrophic lymphoma)
<><><><><><>
Chemical mediators (inflammatory)
◼ Insect bite (venom = vasoactive amines - histamine and serotonin)
◼ Mast cell degranulation, caused by
> Direct injury (scratching): Canine acral dermatitis
> IgE mediated degranulation - Type 1 hypersensitivity
=> Feline eosinophilic skin disease/feline eosinophilic granuloma complex
=> Canine allergic dermatitis, canine atopic dermatitis, ectoparasitism, Cutaneous adverse reaction to food)
Sensory detector system pruritus;
Mast cell degranulation - what is released, effects
Mast cell degranulation releases Vasoactive amines
◼ Histamine (major)
> Vasodilation = Hyperaemia = Erythema
> Increased permeability = Edema = Wheal
> Activates endothelium
◼ Eosinophil chemotactic factor
> Eosinophils attracted
<><><><>
DERMPATH Pattern = PERIVASCULAR DERMATITIS, often Eosinophilic type
- Sensory nerve or neural processor disease
- categories
Direct stimulation of the nerve by
◼ Phantom limb
◼ Traumatic neuroma
◼ Nerve sheath tumors
Sensory nerve or neural processor disease: no primary skin disease
- what conditions are in this category? causes?
Canine acral mutilation
◼ Idiopathic
◼ Phantom‘limb’
◼ Arnold Chiari syndrome and syringomyelia Cavalier King Charles spaniels
<><><><>
Canine acral dermatitis (‘lick granuloma’)
◼ Preexistent condition
◼ idiopathic
<><><><>
Feline idiopathic ulcerative dermatosis
◼ Psychogenic alopecia
◼ Paininduced alopecia
Outcome of pruritus
◼ Red skin (erythroderma)
◼ Remove stratum corneum
> Remove skin barrier function – Superficial Pyoderma
◼ Remove stratum basale and spinosum
> Ulceration and exudation - Superficial spreading pyoderma (hot spot)
◼ Epidermal hyperplasia
> Alter skin barrier function – Superficial pyoderma and yeast infection
> Stimulates sebaceous glands – moist seborrhea
◼ Alopecia - from hair breakage
◼ Actinic effects – from alopecia
<><><><><><><><>
Pyoderma = bacterial infection of skin; Actinic = rays - sunrays
Therapy that targets chemical mediators
◼ Antihistamines
◼ Corticosteroids
◼ Cyclosporine
◼ Apoquel (Oclacitinib) - Janus kinases (JAKs) are involved in the signaling of numerous cytokines involved in allergy and inflammation (IL- 2, 4, 6, and 13), and especially IL-31 (cell mediated immunity)
◼ Cytopoint - caninized monoclonal antibody (mAb) against IL- 31.
Gross pathology of skin with pruritic skin disease
◼ Erythema
◼ Wheal
The Language of Skin:
Erythema - definition
- histological term?
Erythema = reddening of the skin
- Histological term: VASCULAR DILATION, often with ENDOTHELIAL HYPERTROPHY
The Language of Skin:
Wheal - definition
- histological term?
- A Wheal is a transient sharply circumscribed raised lesion resulting from dermal edema.
- In common parlance, these are hives.
- Histological term: DERMAL EDEMA
Pruritic skin disease
- how common?
- what do we need to do?
- biopsy? when and why?
◼ 85% of dermatology
◼ Identify cause - majority require clinical elimination
◼ Biopsy
> ONLY when you have eliminated known causes
> to differentiate inflammatory from noninflammatory or neoplastic disease.
** ALWAYS PERFORM DERMATOLOGIC EXAMINATION**
Outcome of pruritus
◼ Self trauma
> Scaling
> Ulceration
> Alopecia
> Actinic effects
◼ PERIVASCULAR DERMATITIS (PVD)
◼ Altered skin barrier function
◼ Secondary Bacterial infection
> Pyoderma (neutrophilic)
Histological Pattern: PERIVASCULAR DERMATITIS
Epidermis
- Compact hyperkeratosis
- Hypergranulosis
- Acanthosis
<><><><>
Dermis
- Vascular dilation
- Edema
- Endothelial hypertrophy
<><><><>
* Common generic reaction of skin to injury.
* Seldom specific.
Types of PVD based on cell type
- cell poor
Cell poor
◼ Xerosis
◼ Canine allergic dermatitis
◼ Canine atopic dermatitis (CAD)
Types of PVD based on cell type
- eosinophilic
◼ Parasites including flea allergy dermatitis
◼ Cutaneous adverse food reaction (CARF; food allergy)
◼ Canine atopic dermatitis (CAD)
Types of PVD based on cell type
- neutrophilic
◼ Bacteria – pyoderma (superficial, deep)
Types of PVD based on cell type
◼ Lymphocytic plasmacytic
◼ Chronic antigenic stimulation - Chronic pyoderma
Types of PVD based on cell type
◼ Histiocytic
◼ Leishmania
Types of PVD based on cell type - summary
◼ Cell poor
> Xerosis
> Canine allergic dermatitis
> Canine atopic dermatitis (CAD)
◼ Eosinophilic
> Parasites including flea allergy dermatitis
> Cutaneous adverse food reaction (CARF; food allergy) > Canine atopic dermatitis (CAD)
◼ Neutrophilic
> Bacteria – pyoderma (superficial, deep)
◼ Lymphocytic plasmacytic
> Chronic antigenic stimulation - Chronic pyoderma
◼ Histiocytic
> Leishmania
