Difference between revisions of "Skin Environmental - Pathology"

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#REDIRECT[[:Category:Integumentary System - Environmental Pathology]]
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==Chemical damage==
 +
===[[Contact Dermatitis]]===
 +
 
 +
===[[Ergot Poisoning]]===
 +
 
 +
 
 +
 
 +
===[[Fescue Poisoning]]===
 +
 
 +
 
 +
===[[Selenium Poisoning]]===
 +
 
 +
 
 +
==Physical damage==
 +
 
 +
===[[Acral Lick Dermatitis]]===
 +
 
 +
===[[Callus]]===
 +
 
 +
===[[Feline Psychogenic Alopecia]]===
 +
 
 +
 
 +
 
 +
===[[Injection Site Reaction]]===
 +
 
 +
 
 +
===[[Intertrigo]]===
 +
 
 +
 
 +
===Pyotraumatic dermatitis===
 +
*Also called '''acute moist dermatitis''' or ''''hot spot''''
 +
*Common in dogs, especially self-inflicted due to pain and itching
 +
*Usual causes: [[Skin Immunologic - Pathology|allergies]], irritants, matted hair, [[Parasitic skin infections - Pathology|parasites]]
 +
*Lesions tend to be worse in hot and humid weather
 +
*Grossly:
 +
**Hairless, red and moist lesion
 +
**Fluid exudate
 +
**Edges are circumscribed and red
 +
*Microscopically:
 +
**Superficial erosive to ulcerative exudative dermatitis
 +
**May be deeper suppurative folliculitis
 +
 
 +
[[Category:Integumentary System - Physical Damage]]
 +
 
 +
 
 +
===Radiation damage===
 +
*Cells sensitive to radiation include [[Skin Glossary - Pathology|anagen]] hair follicles, germinal basal cells, melanocytes and endothelial cells
 +
*Early changes:
 +
**Erythema, epidermal blisters and oedema, erosions and ulceration
 +
**Healed by scarring, hyperpigmentation with lower doses and hypopigmentation with higher doses
 +
**Temporary or permanent alopecia
 +
*Chronic changes:
 +
**Scarring, altered pigmentation, alopecia
 +
**Epidermal and adnexal atrophy
 +
**Degeneration of vascular and elastic tissue
 +
**Fibrosis of dermal and subcutaneous tissue
 +
**Ulceration
 +
**In severe damage, squamous cell carcinoma may develop
 +
 
 +
[[Category:Integumentary System - Physical Damage]]
 +
 
 +
 
 +
===Low temperature damage===
 +
*Prolonged cold can cause ice crystal formation and vascular injury resultic in damage to tissue due to increased intracellular salt concentration
 +
*Slow chilling can cause vasoconstriction, cellular damage -> secondary vasodilation and increased permeability -> oedema
 +
*Severe and persistent cold causes vasoconstriction, increase in blood viscosity and tissue anoxia
 +
*Lesions may occur in wet or hypoglycaemic neonates or animals recently moved from warm to cold environment
 +
*Areas affected are extremities
 +
*Lesions consist of [[Necrosis - Pathology#Gangrene|gangrene]] and necrotic tissue
 +
 
 +
 
 +
[[Category:Integumentary System - Physical Damage]]
 +
 
 +
 
 +
===High temperature damage===
 +
*May result from excessive heat, liquids, flames, friction, lightning, electricity
 +
*Partial or full thickness burns (first, second and third degree burns)
 +
*Full thickness burns:
 +
**Total destruction of skin and adnexa
 +
**Has to be repaired by grafting
 +
**Life threatening
 +
*Partial thickness burns:
 +
**Some structures preserved -> regeneration may occur
 +
**Grossly:
 +
***Erythema (capillary dilation)
 +
***Oedema (increased permeability of capillaries)
 +
***Vesicles
 +
**Microscopically:
 +
***[[Necrosis - Pathology#Coagulation Necrosis|Coagulation necrosis]] of epidermis
 +
***Subepidermal vesiculation
 +
***Necrosis of adnexa
 +
***Degenerated subepidermal collagen
 +
***May involve large numbers of [[Neutrophils|neutrophils]] if secondary ifection is present
 +
 
 +
 
 +
[[Category:Integumentary System - Physical Damage]]
 +
 
 +
==Sunlight damage==
 +
*Transient erythema may develop into sunburn erythema (warmth, swelling, pain)
 +
*Diffusion of inflammatory mediators (''e.g.'' cytokines) from damaged keratinocytes and endothelial cells
 +
*Photooxidation of existing melanin -> pigment darkening
 +
*Melanogenesis
 +
*Immune responses of skin are reduced by UV light
 +
 
 +
 
 +
[[Category:Integumentary System - Sunlight Damage]]
 +
 
 +
 
 +
===Solar dermatosis and neoplasia===
 +
*Caused by chronic sunlight damage
 +
*Damaged tissue generates free radicals than may damage nucleis acids and proteins
 +
*If damage repaired prior to mitosis - no lasting effect
 +
*If mitosis occurs before repair, post-mitotic repair is prone to faults and DNA mutations may result in neoplasia
 +
 
 +
 
 +
[[Category:Integumentary System - Sunlight Damage]]
 +
 
 +
 
 +
===Solar dermatitis===
 +
*Particularly in white animals and where little or no hair is present
 +
*Grossly:
 +
**[[Skin Glossary - Pathology|Erythema, scaling and crusting]]
 +
**-> Wrinkled nand thickened skin
 +
** Squamous cell carcinoma or haemangiosarcoma/haemangioma may develop
 +
*Microscopically:
 +
**Dyskeratotic cells
 +
**Intercellular oedema
 +
**Vacuolated keratinocytes
 +
**Followed by [[Skin Glossary - Pathology|hyperkeratosis, parakeratosis and acanthosis]]
 +
**Endothelial swelling
 +
**Haemorrhage
 +
**Hyperplasia
 +
**Dermal fibrosis
 +
**Dogs may develop actinic [[Skin Glossary - Pathology|comedones]]
 +
 
 +
[[Category:Integumentary System - Sunlight Damage]]
 +
 
 +
===[[Photosensitisation]]===
 +
 
 +
===Photoenhanced dermatoses===
 +
*Many [[Skin Immunologic - Pathology|immune-mediated]] cutaneous disease are made worse by sunlight
 +
**Lupus erythematosus
 +
**Dermatomyositis
 +
**Pemphigus erythematosus
 +
*Vasculitis in extremities, especially white-haired horses
 +
*Grossly:
 +
**Erythematous, well circumscribed crusted lesions or hyperkeratotic [[Skin Glossary - Pathology|plaques]]
 +
*Microscopically:
 +
**Vasculitis of superficial dermal vessels
 +
**Thrombi may be seen
 +
 
 +
[[Category:Integumentary System - Sunlight Damage]]

Revision as of 16:05, 21 February 2011

Chemical damage

Contact Dermatitis

Ergot Poisoning

Fescue Poisoning

Selenium Poisoning

Physical damage

Acral Lick Dermatitis

Callus

Feline Psychogenic Alopecia

Injection Site Reaction

Intertrigo

Pyotraumatic dermatitis

  • Also called acute moist dermatitis or 'hot spot'
  • Common in dogs, especially self-inflicted due to pain and itching
  • Usual causes: allergies, irritants, matted hair, parasites
  • Lesions tend to be worse in hot and humid weather
  • Grossly:
    • Hairless, red and moist lesion
    • Fluid exudate
    • Edges are circumscribed and red
  • Microscopically:
    • Superficial erosive to ulcerative exudative dermatitis
    • May be deeper suppurative folliculitis


Radiation damage

  • Cells sensitive to radiation include anagen hair follicles, germinal basal cells, melanocytes and endothelial cells
  • Early changes:
    • Erythema, epidermal blisters and oedema, erosions and ulceration
    • Healed by scarring, hyperpigmentation with lower doses and hypopigmentation with higher doses
    • Temporary or permanent alopecia
  • Chronic changes:
    • Scarring, altered pigmentation, alopecia
    • Epidermal and adnexal atrophy
    • Degeneration of vascular and elastic tissue
    • Fibrosis of dermal and subcutaneous tissue
    • Ulceration
    • In severe damage, squamous cell carcinoma may develop


Low temperature damage

  • Prolonged cold can cause ice crystal formation and vascular injury resultic in damage to tissue due to increased intracellular salt concentration
  • Slow chilling can cause vasoconstriction, cellular damage -> secondary vasodilation and increased permeability -> oedema
  • Severe and persistent cold causes vasoconstriction, increase in blood viscosity and tissue anoxia
  • Lesions may occur in wet or hypoglycaemic neonates or animals recently moved from warm to cold environment
  • Areas affected are extremities
  • Lesions consist of gangrene and necrotic tissue


High temperature damage

  • May result from excessive heat, liquids, flames, friction, lightning, electricity
  • Partial or full thickness burns (first, second and third degree burns)
  • Full thickness burns:
    • Total destruction of skin and adnexa
    • Has to be repaired by grafting
    • Life threatening
  • Partial thickness burns:
    • Some structures preserved -> regeneration may occur
    • Grossly:
      • Erythema (capillary dilation)
      • Oedema (increased permeability of capillaries)
      • Vesicles
    • Microscopically:
      • Coagulation necrosis of epidermis
      • Subepidermal vesiculation
      • Necrosis of adnexa
      • Degenerated subepidermal collagen
      • May involve large numbers of neutrophils if secondary ifection is present

Sunlight damage

  • Transient erythema may develop into sunburn erythema (warmth, swelling, pain)
  • Diffusion of inflammatory mediators (e.g. cytokines) from damaged keratinocytes and endothelial cells
  • Photooxidation of existing melanin -> pigment darkening
  • Melanogenesis
  • Immune responses of skin are reduced by UV light


Solar dermatosis and neoplasia

  • Caused by chronic sunlight damage
  • Damaged tissue generates free radicals than may damage nucleis acids and proteins
  • If damage repaired prior to mitosis - no lasting effect
  • If mitosis occurs before repair, post-mitotic repair is prone to faults and DNA mutations may result in neoplasia


Solar dermatitis

  • Particularly in white animals and where little or no hair is present
  • Grossly:
  • Microscopically:

Photosensitisation

Photoenhanced dermatoses

  • Many immune-mediated cutaneous disease are made worse by sunlight
    • Lupus erythematosus
    • Dermatomyositis
    • Pemphigus erythematosus
  • Vasculitis in extremities, especially white-haired horses
  • Grossly:
    • Erythematous, well circumscribed crusted lesions or hyperkeratotic plaques
  • Microscopically:
    • Vasculitis of superficial dermal vessels
    • Thrombi may be seen
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