Immune Mediated Dermatoses Flashcards
What do immune-mediated diseases imply vs autoimmune diseases?
- Implies a foreign antigen (protein) that triggers an immunological reaction
Antigens that can trigger an immunological reaction
- Drugs!
- Bacteria
- Viruses
Severity of immune-mediated diseases
- Often very acute and very severe
What’s important for immune-mediated diseases?
- Thorough history is extremely important
- Travel history
- Consider tickborne diseases
- Drug hx
- vaccine history
Vasculitis
- Characterized by inflammation and destruction of blood vessels, resulting in ischemic necrosis
- Poor blood supply to the skin leads to ischemic dermatopathy
Pathophysiology of Vasculitis
- 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
Triggering causes of vasculitis
- Idiopathic (up to 50%)
- Infectious
- Drugs
- Immune-mediated
Who gets idiopathic vasculitis?
Jack Russell Terriers
Infectious causes of vasculitis
- Bacterial
- Viral (Parvo, Coronavirus)
- Protozoal (Leishmania, Sarcocystis)
- Rickettsial (RMSF, Ehrlichia, Babesia)
- Fungal
Drugs that can lead to vasculitis
- Injection of foreign proteins (Rabies vax!)***
- Antibiotics
- Ivermectin
- Itraconazole
- Fenbendazole
Immune-mediated causes of vasculitis
- Systemic lupus erythematosus
- Rheumatoid arthritis
What causes Rabies vaccine induced vasculitis?
- Detected in blood vessels and epithelium of hair follicles
Breeds at risk for Rabies Vaccine induced vasculitis?
- Poodles
- Silky terrier
- Pekingese
- Maltese
- Bichon frise
Initial clinical signs of Rabies vaccine induced vasculitis
- 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
How long can signs occur after vaccination for rabies vax induced vasculitis?
- 2-8 months after
Differentials for ear tip vasculitis
- Pemphigus
- Ectoparasites like Scabies or Notoedres (but these are very itchy)
Appearance of ear tip vasculitis
- Exposure of cartilage and shaking (if cartilage is exposed, it’s painful)
- Characteristic notching
- Only affects the inner ear
- Clinical diagnosis
What to do if you suspect rabies is the triggering cause of vasculitis?
- DO NOT vaccinate
- Consider rabies antibody titers
Example history for a dog with vaccine induced vasculitis
- 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
Treatment for Rabies vaccine induced vasculitis
- Pentoxyfilline
- Doxycycline/niacinamide
Pentoxifylline type of drug
- Methylxanthine
Pentoxyfylline MOA
- Potent hemorrheologic and anti-inflammatory properties
- Improves microcirculation
- Inhibits cytokines (IL-1, IL-6, TNFa)
- Inhibits leukocyte and platelet adhesion to endothelial cells
How long can it take for pentoxifylline to become effective?
- Approximately 6-8 weeks
Doxycycline/niacinamide MOA
- Inhibits matrix metalloproteases
- Anti-inflammatory properties
How long can it take for doxycycline/niacinamide to be effective?
- 6-8 weeks
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
What might you consider for very severe and non-responsive cases of vasculitis
- Amputation of ear tips in very severe cases
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
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?
What is the word for separation of nails from the quick?
- Onycholysis
What is the word for splitting of the claws?
- Onychoschizia
Diagnosis of symmetrical lupoid onychodystrophy
- Clinical
- Consider causes of vasculitis (rabies or other vaccines; tick borne; drugs)
- Biopsies not recommended
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
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
What is erythema multiforme?
- Reaction pattern described by pathologists on histopathology
- Epidermal/keratinocyte apoptosis with lymphocytic satellitosis
Pathogenesis of erythema multiforme
- Unknown
- T cell infiltration and activation –> keratinocyte apoptosis
- Many possible triggers
Reported triggers of erythema multiforme
- Drug reactions
- Food allergies
- Neoplasia
- Infections like parvo
- Idiopathic (old dog EM)
Drugs that can trigger erythema multiforme
- Antibiotics (sulfa, cephalosporins, MANY more)
- Other drugs (phenobarbital, levothyroxine, many more)
Clinical signs of erythema multiforme
- Acute
- May affect skin and mucous membranes
- ERythematous macules
- Target lesions
- Bullae/vesicles
- Crust
- More plaque like crustin g
Differentials for erythema multiforme
- Pemphigus vulgaris
- Cutaneous lymphoma
- Thermal burn
Diagnosis of erythema multiforme
- Biopsy!
What does biopsy show with erythema multiforme?
- Epidermal/keratinocyte apoptosis with lymphocyte satellitosis
Treatment of erythema multiforme?
- Look for underlying cause
- Drug history
- Food allergy!
- Neoplasia screen
- Cyclosporine? Prednisone?
What should you always think with itching/licking paws/overgrooming?
- ALLERGIES UNTIL PROVEN OTHERWISE
