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What are the most common autoimmune skin diseases on dogs are cats? (2)
pemphigus foliaceus (PF) and discoid lupus erythematosus (DLE)
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How does autoimmunity occur? (4)
exposure to previously hidden antigens, change in T cell activity (loss of suppression or auto-reactive response), antigen mimicking (infectious agents, drugs), genetic influences
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With PF, autoantibodies are _______ and are directed against ___________.
IgG; desmocollins (part of the desmosomes)
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How does acantholysis occur with PF?
IgG binds to desmocollins, causing the release of enzymes that degrade the desmosomes
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Pemphigus is also seen in __(2)__; these diseases should be differentials and can be ruled out by __________.
suppurative skin disease and dermatophytosis caused by Trichophyton mentagrophytes; biopsy
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What is the hallmark of pemphigus diseases?
acantholytic keratinocytes- immature, detached keratinocytes
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What are the forms of pemphigus? (2)
- Superficial: foliaceus/erythematosus; lesion forms underneath the stratus corneum or within stratum granulosum
- Deep: vulgaris; lesion forms just above the basal cell layer
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What are the most common complaints with PF and p. vulgaris, respectively?
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What are primary lesions of PF? (1)
pustules (rupture very easily, usually don't see this by the time they come in)
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What are secondary lesions of PF? (6)
crusts, scales, alopecia, erosions, erythema, +/- pruritus variable [this is usually what we see clinically]
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What is the distribution of lesions with PF? (6)
muzzle (dorsal aspect), pinnae, footpads (hyperkeratotic, crusty), paronychia (more common in cats), general distribution, [very rarely] oral mucosa
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What are your differentials that may look like PF? (8)
bacterial folliculitis, dermatophytosis, demodicosis, P. erythematosus, DLE, superficial necrolytic dermatitis, zinc responsive dermatosis, cutaneous lymphoma
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There is crusting and involvement of the footpads. What are your differentials? (3)
PF, superficial necrolytic dermatitis, zinc responsive dermatosis
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What are skin cytology findings with PF? (3)
multiple acantholytic keratinocytes, non-degenerate neutrophils, +/- eosinophils
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How is a diagnosis of PF confirmed?
biopsy- subcorneal or intraepidermal pustules with acantholytic keratinocytes
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Benign form of superficial pemphigus that has similarities to DLE.
pemphigus erythematosus
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P. erythematosus is usually localized to the ____(3)_____.
face and pinna and nasal planum
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PF has _______ ANA (anti-nuclear antibodies); PE has _______ ANA titers.
negative; negative or low (non-diagnostic)
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Lesions with p. erythematosus are aggravated by _________.
UV light
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What is different between localization of PF and PE?
PE often involves the actual nasal planum and nose; PE stays localized to the face usually
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Secondary lesions of PE. (4)
crusts, erosion, alopecia, erythema
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Primary lesion of PE.
pustules (not usually present)
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Describe the onset of PE. (2)
gradual onset, lesions worse with UV exposure
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Describe histo findings with PE. (3)
subcorneal or intraepidermal pustules, basal keratinocytes vacuolization, and presence of apoptotic cells in basal layer
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The ulcerative, deep, and most severe form of pemphigus.
pemphigus vulgaris
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What are common seconadary lesions with PV? (4)
erosions, deep ulcers, crusts, pain
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What non-dermatologic signs are present with PV? (3)
pyrexia, anorexia, depression
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Describe the distribution of PV. (4)
oral cavity (almost all cases), mucocutaneous junctions (eyes, mouth, genitals, anus), paronychia, frictional areas (axillae, inguinal)
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With which form of pemphigus do we see systemic signs?
pemphigus vulgaris
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Cytologic findings with PV. (2)
acantholytic keratinocytes and neutrophils
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What are histo findings with PV? (3)
suprabasilar acantholysis and cleft forming vesicles or pustules containing acantholytic keratinocytes, neutrophils
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What is the characteristic finding on histo for PV?
tombstone appearance of basal cells
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When are general principals of therapy for pemphigus? (3)
lifelong (will be on drugs for life), immune suppression, can be controlled/ go into remission with appropriate therapy
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What are topical therapies that can be adjunctive treatments for pemphigus? (3)
waterproof sunscreen (DLE, SLE, PE), vitamin E (DLE, SLE), topical corticosteroids
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Why is Vitamine E used as adjunctive treatment for SLE and SLE? What is important to remember about this supplement?
antioxidant that stabilizes lysosomes; lag phase 6-12 weeks, so give it time to work
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What antibiotics are used to control autoimmune skin diseases? (4) How does this work?
tetracycline (Doxycycline, Minocycline), Niacinamide; unknown MOA- inhibits neutrophil chemotaxis and release of proteases
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What topical steroid is good for long term use?
hydrocortisone 1-2%
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What is the most effective steroid for use in cats?
Triamcinolone
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What oral steroids are commonly used in dogs with autoimmune skin diseases? (3)
prednisone, prednisolone, dexamethasone
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What is the MOA of Azathioprine?
interferes with synthesis of nucleic acids, cytotoxic to T cells
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How is Azathioprine used?
can be used as glucocorticoid sparing agent (to allow you to decrease steroid dose) or as sole therapy
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Azathioprine is contraindicated in __________.
cats (b/c causes severe myelosuppression)
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What is the MOA of Chloambucil?
alkylating agent, affects crosslinking of DNA
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Is Chlorambucil safe in cats?
yes
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What is the MOA of cyclosporine and tacrolimus?
immunosuppresant agents that suppress cytokine production (IL-2) and T cell proliferation [note: tacrolimus is topical]
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What is the MOA of mycophenelate mofetil?
inhibits inosine monophosphate dehydrogenase, which is the rate limiting enzyme in certain DNA synthesis--> inhibits proliferative responses of T and B cells
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With DLE, _________ is affected; it is exacerbated by __________.
only skin; UV light
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How do DLE lesions usually start? How can they progress?
depigmentation and erythema of the planum nasale; may progress to erosions, ulcers, scaling, and crusts; lesions heal with a scar
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What is the distribution of lesions with DLE? (5)
often limited to planum nasale and dorsal aspect of muzzle; may include mucocutaneous junctions, scrotum, pinnae
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What are differential diagnoses that may look like DLE? (4)
PE, PE, dermatomyositis, zinc responsive dermatosis
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What are clinical signs of DLE? (5)
depigmentation, crusting, ulcers, erythema, and crusts on the nose
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How do you diagnose DLE?
Biopsy non-ulcerated, depigmented lesions: interface dermatitis characterized by hydropic-vcuolar changes at the BM and basal cell layer
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How do you treat DLE? (7)
tacrolimus, doxycyline, niacinamide, cyclosporine, glucocorticoids, Vit E, sunscreen
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Ulcerative dermatitis affecting predominantly the ventrum of Shelties, Collies, +/- Border Collies.
vesicular cutaneous lupus erythematosus
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Where are lesions associated with VCLE usually located? (2)
mucocutaneous junctions and concave aspect of pinnae
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How has VCLE been managed? (8)
glucocorticoid/azathioprine, doxycycline, cyclosporine, tetracycline/niacinamide, tacrolimus, sun avoidance
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Exfoliative cutaneous lupus erythematosus occurs in ____________; associated lesions include...(5)
german short-haired pointers; scaling, alopecia, erythema, erosions, ulcers
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What is the distribution of lesions with exfoliative cutaneous lupus erythematosus? (4)
muzzle, pinnae, dorsum, may become generalized
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How is exfoliated cutaneous lupus erythematosus managed, and how does it respond?
steroids; progressive and poorly responsive to treatment
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Describe SLE.
generalized connective tissue disorder that usually involves many organ systems
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What characterizes SLE?
presence of anti-nuclear antibodies (ANAs)
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What is the pathogenesis of SLE?
viral, genetic, and immunological factors have been postulated as etiologies--> multiple autoantibodies produced and are responsible for clinical signs
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What lesions might be present as cutaneous manifestations of SLE? (7)
macropapular, discoid, pruritic, urticarial, vesiculobullous, or seborrheic eruptions, depigmentation****
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Where are lesions usually located with SLE?
anywhere- usually symmetrical
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What are clinical signs associated with SLE? (5)
polyarthritis, skin lesions, glomerulonephritis, hemolytic anemia, thrombocytopenia
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How is SLE diagnosed? (6)
Biopsy: interface dermatitis, vacuolar changes of the basal cells, vesicles and ulcers, thickened BM, individual apoptotic keratinocytes; ANA positive (90% of cases)
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What is the prognosis for SLE?
guarded to good, may have periods of remission; guarded if glomerulonephritis is present
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3 common diseases that are difficult to control and may ultimately lead to euthanasia (thus, life-threatening)?
AD, canine generalized demodicosis, otitis externa/media
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What canine generalized demodex cases are hardest to manage and why?
cases with concurrent allergies because allergy medications suppress the immune system, which is contraindicated when treating demodex
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What systemic diseases have skin manifestations? (5)
hypothyroidism, hyperadrenocorticism, paraneoplastic syndromes (thymoma, pancreatic adenocarcinoma, paraneoplastic pemphigus)
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Describe thymoma-associated exfoliative dermatosis. (6)
severe scaling and erythema, alopecia on head/neck/pinnae, anorexia/lethargy (systemic signs), respiratory signs, OLDER CAT RED FLAG (esp if never had skin dz before)
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How do you diagnose thymoma associated exfoliative dermatosis?
- skin biopsy: interface dermatitis with exocytosis of lymphocytes, apoptotic keratinocytes, satellitosis, marked hyperkeratosis, absent sebaceous glands
- rads: mediastinal mass
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What neoplasias are associated with paraneoplastic alopecia? (3)
pancreatic adenocarcinoma, bile duct carcinoma, hepatocellular carcinoma
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What is "glistening skin" with alopecia characteristic of?
paraneoplastic alopecia
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What drugs are most commonly associated with cutaneous adverse drug reaction? (5)
sulfonamides, penicillins, cephalosporins, levasimole, dietyl carbamazine
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What ist he postulated pathogenesis of erythema multiforme? (6)
drug reactions, bacterial infections, food adverse reactions, neoplasia, parvovirus, herpes?
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What is the clinical presentation of erythema multiforme? (5)
target lesions (more variable in animals than people), erythematous macules, urticarial plaques, vesicles, ulcers
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How do you diagnose erythema multiforme?
biopsy
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How do you manage erythema multiforme? (5)
mild-none, glucocorticoids, azathioprine, cyclosporine, pentoxifylline
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Toxic epidermal necrolysis is __________ that is usually associated with _________.
extensive "vesiculo-bullous" and ulcerative; drug reactions
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How do you diagnose toxic epidermal necrolysis? (2)
- nikolsky sign: gentle skin manipulation results in sloughing
- biopsy
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How do you manage toxic epidermal necrolysis? (4)
withdrawal suspected drug, fluid therapy, wound management, immunosuppression (caution if infection)
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Cutaneous reaction pattern caused by diseases where blood vessel walls are the target of an inflammatory response.
cutaneous vasculitis
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Lesions associated with cutaneous vasculitis. (7)
purpura, hemorrhagic bullae, necrosis, ulcers, urticaria, atrophic skin, alopecia
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What are common locations for cutaneous vasculitis? (8)
paws, pinnae, low legs, claws, lips, tail, scrotum, oral mucosa
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How do you diagnose cutaneous vasculitis? (3)
history of drugs and vaccines, rule out infectious diseases, biopsy
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How do you manage cutaneous vasculitis? (5)
address primary cause, doxycycline/niacinamide, pentoxifylline, tacrolimus, immunosuppression
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