Immune Mediated Dermatoses Flashcards

1
Q

What do immune-mediated diseases imply vs autoimmune diseases?

A
  • Implies a foreign antigen (protein) that triggers an immunological reaction
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2
Q

Antigens that can trigger an immunological reaction

A
  • Drugs!
  • Bacteria
  • Viruses
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3
Q

Severity of immune-mediated diseases

A
  • Often very acute and very severe
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4
Q

What’s important for immune-mediated diseases?

A
  • Thorough history is extremely important
  • Travel history
  • Consider tickborne diseases
  • Drug hx
  • vaccine history
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5
Q

Vasculitis

A
  • Characterized by inflammation and destruction of blood vessels, resulting in ischemic necrosis
  • Poor blood supply to the skin leads to ischemic dermatopathy
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6
Q

Pathophysiology of Vasculitis

A
  • Type III hypersensitivity
  • Antigen-antibody complex lodges into the endothelium of blood vessels leading to a complement cascade (C1, C5a, C3b)
  • C5a recruits neutrophils leading to release of lysozomal enzymes
  • These enzymes recruit macrophages and mast cells and lead to a lot of damage
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7
Q

Triggering causes of vasculitis

A
  • Idiopathic (up to 50%)
  • Infectious
  • Drugs
  • Immune-mediated
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8
Q

Who gets idiopathic vasculitis?

A

Jack Russell Terriers

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9
Q

Infectious causes of vasculitis

A
  • Bacterial
  • Viral (Parvo, Coronavirus)
  • Protozoal (Leishmania, Sarcocystis)
  • Rickettsial (RMSF, Ehrlichia, Babesia)
  • Fungal
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10
Q

Drugs that can lead to vasculitis

A
  • Injection of foreign proteins (Rabies vax!)***
  • Antibiotics
  • Ivermectin
  • Itraconazole
  • Fenbendazole
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11
Q

Immune-mediated causes of vasculitis

A
  • Systemic lupus erythematosus

- Rheumatoid arthritis

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12
Q

What causes Rabies vaccine induced vasculitis?

A
  • Detected in blood vessels and epithelium of hair follicles
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13
Q

Breeds at risk for Rabies Vaccine induced vasculitis?

A
  • Poodles
  • Silky terrier
  • Pekingese
  • Maltese
  • Bichon frise
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14
Q

Initial clinical signs of Rabies vaccine induced vasculitis

A
  • Circular area of alopecia at the site of the vaccine
  • Looks like dermatophytosis but no active inflammation
  • Signs can be seen 2-8 months after vaccination
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15
Q

How long can signs occur after vaccination for rabies vax induced vasculitis?

A
  • 2-8 months after
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16
Q

Differentials for ear tip vasculitis

A
  • Pemphigus

- Ectoparasites like Scabies or Notoedres (but these are very itchy)

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17
Q

Appearance of ear tip vasculitis

A
  • Exposure of cartilage and shaking (if cartilage is exposed, it’s painful)
  • Characteristic notching
  • Only affects the inner ear
  • Clinical diagnosis
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18
Q

What to do if you suspect rabies is the triggering cause of vasculitis?

A
  • DO NOT vaccinate

- Consider rabies antibody titers

19
Q

Example history for a dog with vaccine induced vasculitis

A
  • Chief complaint: non-pruritic, progressive hair loss
  • History of discoloration on ear tips for last 3 years
  • Non-pruritic alopecia of right axilla/chest and digits starting in April 2010
  • No meds
  • Vaccinated in Feb 2010 in the right shoulder area
  • In June, skin scrapes were neg for demodex
  • Treated with ketoconazole for possible yeast infection
  • No improvement noted by owner
  • ruled out tick borne disease
  • After thorough drug and vaccine history, clinical diagnosis made
  • Biopsy - seeing active vasculitis is rare to difficult but other changes could support
20
Q

Treatment for Rabies vaccine induced vasculitis

A
  • Pentoxyfilline

- Doxycycline/niacinamide

21
Q

Pentoxifylline type of drug

A
  • Methylxanthine
22
Q

Pentoxyfylline MOA

A
  • Potent hemorrheologic and anti-inflammatory properties
  • Improves microcirculation
  • Inhibits cytokines (IL-1, IL-6, TNFa)
  • Inhibits leukocyte and platelet adhesion to endothelial cells
23
Q

How long can it take for pentoxifylline to become effective?

A
  • Approximately 6-8 weeks
24
Q

Doxycycline/niacinamide MOA

A
  • Inhibits matrix metalloproteases

- Anti-inflammatory properties

25
How long can it take for doxycycline/niacinamide to be effective?
- 6-8 weeks
26
How does Dr. Mel use doxycycline/niacinamide for vasculitis treatment?
- Used with pentoifylline if pentoxy isn't successful | - He doesn't use this right away
27
What might you consider for very severe and non-responsive cases of vasculitis
- Amputation of ear tips in very severe cases
28
Symmetrical lupoid onychodystrophy - what is it? How common? Etiology?
- Acute onset nail loss - Uncommon claw disease - Unknown etiology - Suspected to have a vasculitic, immune-mediated component
29
Clinical signs of symmetrical lupoid onychodystrophy?
- Acute onset of nail loss - May affect only a few but will progress - Can be painful - Dogs may lick - SEparation of nails from quick - Splitting of claws - Secondary digit infections?
30
What is the word for separation of nails from the quick?
- Onycholysis
31
What is the word for splitting of the claws?
- Onychoschizia
32
Diagnosis of symmetrical lupoid onychodystrophy
- Clinical - Consider causes of vasculitis (rabies or other vaccines; tick borne; drugs) - Biopsies not recommended
33
Treatment of symmetrical lupoid onychodystrophy
- Treat secondary infections (mal odor? swollen digits? would it be superficial or deep?) - Treat for 6-8 weeks - WHich antibiotic? (ideally culture!) - Pentoxyifylline - Doxy/niacinamide in addition if not responding - Keep claws short
34
What is an important part of managing symmetrical lupoid onychodystrophy?
- Keep claws short, as they will regrow abnormal - Goal is abnormally normal - Filing or dremmel are helpful
35
What is erythema multiforme?
- Reaction pattern described by pathologists on histopathology - Epidermal/keratinocyte apoptosis with lymphocytic satellitosis
36
Pathogenesis of erythema multiforme
- Unknown - T cell infiltration and activation --> keratinocyte apoptosis - Many possible triggers
37
Reported triggers of erythema multiforme
- Drug reactions - Food allergies - Neoplasia - Infections like parvo - Idiopathic (old dog EM)
38
Drugs that can trigger erythema multiforme
- Antibiotics (sulfa, cephalosporins, MANY more) | - Other drugs (phenobarbital, levothyroxine, many more)
39
Clinical signs of erythema multiforme
- Acute - May affect skin and mucous membranes - ERythematous macules - Target lesions - Bullae/vesicles - Crust - More plaque like crustin g
40
Differentials for erythema multiforme
- Pemphigus vulgaris - Cutaneous lymphoma - Thermal burn
41
Diagnosis of erythema multiforme
- Biopsy!
42
What does biopsy show with erythema multiforme?
- Epidermal/keratinocyte apoptosis with lymphocyte satellitosis
43
Treatment of erythema multiforme?
- Look for underlying cause - Drug history - Food allergy! - Neoplasia screen - Cyclosporine? Prednisone?
44
What should you always think with itching/licking paws/overgrooming?
- ALLERGIES UNTIL PROVEN OTHERWISE