Derm1- Pruritus 1

  1. How can an owner recognize pruritus in pets? (6)
    scratching, biting, chewing, licking, gnawing, rubbing
  2. How can clinicians recognize pruritus? (6)
    alopecia, erythema, excoriations, lichenification, hyperpigmentation, scaling [absence of these lesions does not rule out pruritus]
  3. What are mediators of pruritus? (6)
    vasoactive amines (Histamines, serotonin, PAF), eicosanoids (prostaglandin, leukotrienes), proteases (cathepsin, trypsin, fibrinolysin), peptides (neuropeptides), cytokines (IL-31)
  4. What are the 3 phases of the pathophysiology of canine allergic skin disease?
    • 1: initiation
    • 2: sensitization
    • 3: progression
  5. Describe the initiation phase of canine allergic skin disease.
    percutaneous absorption of allergens through a defective stratum corneum
  6. Describe the sensitization phase of canine allergic skin disease.
    naive langerhans cells (LC) capture and internals allergens--> allergen processed/packaged on LC surface and presented to naive Th cells in LN--> cytokines IL-4 and IL-13 produced--> B cells stimulated and produce allergen-specific IgE--> Th migrate to skin--> IgE enters circulation and bind to cells
  7. Describe the progression phase of canine allergic skin disease.
    re-exposure to allergen--> LC with allergen-specific IgE bind allergen--> present allergen to lymph in dermis--> cystokines released IL-31 activate neurons--> itchy--> proinflammatory cytokines--> epidermis thickens, barrier deteriorates, allergen penetration--> cycle continues
  8. Mediators of pruritus are released in close proximity to ____________; signals are received by the _________ and ___________.
    primary afferent nerves; dorsal root ganglia; dorsal horn of spinal cord
  9. Describe the threshold phenomenon and summation effect.
    animals can tolerate a certain load of stimuli causing pruritus; stimuli from co-existent disease are additive (more than 1 allergen at once)
  10. Pruritic skin disease that is a result of hypersensitivity to environmental allergens.
    atopic dermatitis
  11. Immunologically mediated adverse response to food.
    food allergy
  12. Abnormal, physiologic response to a food.
    food intolerance
  13. 3 most common allergic causes of pruritus in SA?
    flea allergy dermatitis, cutaneous adverse food reaction (food allergy), atopic dermatitis
  14. What are the 2 most common infectious causes of pruritus in SA?
    pyoderma and Malassezia (yeast) dermatitis
  15. What are the 3 most common parasitic causes of pruritus in SA?
    Sarcoptes, Notodres (sarcoptic mange); Demodex gatoi (cats only- the only itchy demodex); Cheyletiella
  16. How do you characterize pruritus?
    body site/location, seasonality, intensity, age at onset, itchy or skin lesions first, helpful treatments
  17. What are the body sites affected with scabies? (3)
    ear pinna, elbow, hock
  18. What are the body sites affected with food allergy and atopic dermatitis? (4)
    ventrum, facial (periocular and perioral), otitis (ear canal), distal limbs
  19. What are the body sites affected by flea allergy dermatitis? (3)
    dorsal tail head, ventral groin region/tail, and rump
  20. What are the possible seasonalities of pruritic disorders?
    seasonal, non-seasonal, seasonally non-seasonal (itchy all year but gets worse at certain times)
  21. What are the 3 most common seasonal causes of pruritus?
    FAD, atopic dermatitis, insect hypersensitivity
  22. What are the 5 most common non-seasonal causes of pruritus?
    CAFR, atopic dermatitis, sarcoptic mange, FAD (in warm climates, infested house), infections
  23. What 3 diseases generally have to most intense pruritus [dogs]?
    sarcoptic mange, FAD, CAFR
  24. When does atopic dermatitis usually present in the animal's lifetime?
    usually 1-3 years old
  25. When does CAFR usually present in the animal's lifetime?
    less than 6 months old or greater than 7 years old
  26. When do flea allergy dermatitis and ectoparasite pruritus usually present in the animal's lifetime?
    usually less than 6 months old
  27. Does Demodex cause pruritus?
    NO; the only species of Demodex that causes pruritus is gatoi in cats (also the only contagious species of Demodex)
  28. How is pruritic disease in cats different from dogs?
    harder to recognize, body location of scratching not as distinctive, different skin lesions [non-inflammatory alopecia, miliary dermatitis, eosinophilic dermatitis more common; excoriations, lichenification, hyperpigmentation are rare]
  29. What historical questions are important to ask the owner when approaching a pruritic patient? (5)
    try to localize lesion, ask about seasonality and age of onset, ask about chronicity, ask if pruritus or skin lesions were first, have any treatments worked in the past
  30. How do you handle residual pruritus after secondary infections have been cleared?
    work up the animal for allergic diseases and ectoparasites
  31. How do you handle residual lesions without pruritus after secondary infections have been cleared?
    work up for endocrinopathies, keratinization disorders, autoimmune disorders, Demodex, etc.
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Derm1- Pruritus 1
vetmed derm1