Lecture 14 3/25/25 Flashcards
What is the pathomechanism of uveodermatological syndrome?
specific destruction of melanocytes
Which lesions are seen in uveodermatological syndrome?
-depigmentation
-leukotrichia/white hair
-deep erosion/ulcer
-loss of cobblestone appearance
Which breed commonly presents with uveodermatological syndrome?
akitas
What ocular syndrome is seen in uveodermatological syndrome?
acute onset of bilateral granulomatous uveitis
How does the presence/absence of pigmentation and cobblestone appearance help to differentiate conditions?
-normal: pigmentation and cobblestone both present
-uveodermatological syndrome: pigmentation and cobblestone both absent
-vitiligo: pigmentation absent, cobblestone present
How is uveodermatological syndrome diagnosed?
-histopathology showing lichenoid dermatitis and pigmentary incontinence
-ophthalmic exam showing bilateral uveitis
What is the treatment for uveodermatological syndrome?
immunosuppression
What are the three main immune-mediated dermatoses?
-erythema multiforme
-stevens-johnson syndrome
-toxic epidermal necrolysis
What is the mortality rate for toxic epidermal necrolysis in animals?
around 100%
What is the pathomechanism of erythema multiforme/stevens-johnson syndrome/toxic epidermal necrolysis?
cytotoxic lymphocyte responses against altered keratinocytes, triggered by infectious agents or drugs
what are the causes of erythema multiforme minor/major?
-significant number is idiopathic
-drug reactions account for 19% of minor cases and 59% of major cases
What are the causes of stevens-johnson syndrome and toxic epidermal necrolysis?
-mostly triggered by drugs; NSAIDs and antibiotics
-occasionally triggered by infectious agents
What are the clinical signs of EM minor?
-less than 10% of body surface affected
-raised targetoid lesions
-0 or 1 mucosal surfaces involved
-no systemic signs
What are the clinical signs of EM major?
-less than 10% of body surface affected
-flat or raised targetoid lesions
-more than 1 mucosal surface involved
-systemic signs
What are the clinical signs of SJS?
-less than 10% of body surface affected
-flat erosions/ulcers
-more than 1 mucosal surface involved
-systemic signs
What are the clinical signs of TEN?
-greater than 30% of body surface affected
-flat erosions/ulcers
-more than 1 mucosal surface involved
-systemic signs
How does the clinical presentation of EM differ from SJS/TEN?
EM:
-targetoid lesion
-well-circumscribed ulceration
SJS/TEN:
-coalescing macules and patches
-widespread ulceration
-multiple mucosal surfaces involved
What is the Pseudo-Nikolsky sign?
indication of epidermal detachment; touching the skin is enough to cause erosion
What findings on histopath allow for EM diagnosis?
individual keratinocyte apoptosis at the multiple epidermal levels
What findings on histopath allow for SJS/TEN diagnosis?
full thickness coagulation necrosis
How else are EM, SJS, and TEN differentiated for diagnosis?
clinical presentation
What is the treatment for EM, SJS, and TEN?
-drug withdrawal
-immunosuppression for EM; controversial for SJS/TEN due to sepsis risk
-advanced supportive therapy for SJS/TEN
What is the pathomechanism of cutaneous vasculitis?
blood vessel walls become targets of an inflammatory response (type III hypersensitivity)
What are the potential causes of cutaneous vasculitis?
-vaccines
-vector-borne infection
-drugs
-SLE
-idiopathic
What are the lesions seen in cutaneous vasculitis?
-ulcer
-scarring
-urticaria
-purpura
Which lesions are associated with acute phase cutaneous vasculitis?
-erythematous urticaria (diascopy +)
-petechia
-purpura
-edema
Which lesions are associated with chronic phase cutaneous vasculitis?
-“wedge-shaped” necrotic ulcer
-crust
-alopecia
-scarring/ischemic dermatopathy
What is diascopy?
pressing a slide to the skin to look for blanching
What are potential diagnoses based on diascopy result?
-positive diascopy/blanching: vascular inflammation
negative diascopy/no blanching: hemorrhage or non-vascular inflammation
What is the distribution of lesions in cutaneous vasculitis?
-at extremities
-ear tips
-tail tip
-center of paw pads
-claws
How is cutaneous vasculitis diagnosed?
-typical clinical presentation
-history
-histopath. taken from CENTER showing vasculitis (acute) or ischemic dermatopathy (chronic)
How is cutaneous vasculitis treated?
-avoidance of trigger
-elimination of infectious triggers
-immunosuppression
What is the use of primary immunosuppressant agents?
initial therapy for a short course
Which drug class is used as a primary immunosuppressant agent?
glucocorticoids
What is the use of secondary immunosuppressant agents?
maintenance therapy for a long course
Which drugs are used as secondary immunosuppressant agents?
-cyclosporine
-oclacitinib/apoquel
-azathioprine
-mycophenolate mofetil
How do glucocorticoids work?
-regulation of multiple mediators
-prevent arachidonic acid cascade
-increase anti-inflammatory cytokine production
-decrease inflammatory cytokine production
How does cyclosporine work?
inhibition of T cells
How does oclacitinib/apoquel work?
inhibition of JAKs
How do azathioprine and mycophenolate mofetil work?
inhibition of lymphocytes
