Pemphigus/pemphigoid (NAVDF Tham + Olivry acantholytic 2009 review, Tham Deep Pemphigus review 2020, Tizard Autoimmune) Flashcards
What layer of epidermis does pemphigus foliaceus affect
Stratum spinosum + Stratum granulosum
What layer of epidermis does pemphigus vulgaris affect
Stratum basale
Major autoantigen for canine PF
DSC-1
Major autoantigen in PF in humans
DSG-1
Major autoantigen of PF in cats
Unknown.
Anti-keratinocyte IgG in 23/30 cats in 1 study
What is the etiology of PF usually?
*Spontaneous
Possibly UV triggered
Other triggers:
*Drug/insecticide
What drugs can cause PF in dogs?
*TMS
*Topical ketoconazole
*Insecticide (Promeris, Certifect (Amitraz/ metaflumizone), Vectra 3D. Nexgard!)
*Oxacillin, ampicillin, cephalexin
No drug challenged performed, so cannot CONFIRM it was drug
What drugs can cause PF in cats?
*Cimetidine
*Doxycycline
*Econazole/Neomycin/Triamcinolone/Amoxicillin
*Itraconazole/lime sulfur
What is ENDEMIC pemphigus foliaceus?
*Fogo salvagem (Brazil)
*Sand fly salivary antigen LJM11
Also: young, poor women in S Tunisia. High temp, UV radiation, contact with ruminants, infections, genetic susceptibility
IgE to insect, then transforms to TgG4 against Dsg1 on keratinocytes
Pathomechanism of endemic PF
*Body makes IgG4 (instead of nonpathogenic IgG1) against sandfly salivary antigen
*IgG4 binds to EC1 and EC2 of DSG1
*DSG1 then cannot function for cell adhesion –> acantholysis
Sandfly salivary antigen that can trigger PF
LJM11
Canine PF clinical distribution types
*Facial dominant
*Generalized
*Footpad exclusive
*Trunk-dominant
Is the ability to detect anti-DSC1 IgG lower in trunk-dominant or facial PF? (Bizikova 2022)
Trunk dominant has lower anti-DSC IgG (58%) compared to facial dominant PF (100%)
T or F: Absence of anti-DSC IgG can be used to rule out PF
FALSE.
Many dogs with trunk-dominant PF do not have detectable anti-DSC IgG, even though their major autoantigen is still DSC-1
How can you differentiate between trunk-dominant PF, pustular dermatophytosis, and pyoderma?
*Dermatophytosis: centrifugal expansion of lesions
*Pyoderma: footpads shouldn’t be affected
What are the clinical distribution types of feline PF?
*Claw fold exclusive (11%)
*Periareolar region (10%)
In addition to facial regions
Treatment canine PF
*Oral glucocorticoids to induce remission
*Consider PULSE GCs
+/- steroid-sparing agents
*Azathioprine
*Cyclosporine
*Mycophenolate
*Apoquel
+/- adjunct immunomodulatory drugs
*Doxy/niacinamide (only 1/8 dogs benefit)
*Polysulfated glucosaminoglycans (usually arthritis tx; can act as steroid sparing agent! Mechanism: inhibition of proteases in complement cascade?? Reduces inflammatory cell migration??)
IF REFRACTORY:
*IVIG (efficacy may reduce over time)
IN THE FUTURE:
*Bruton’s tyrosine kinase inhibitor (BTKi)
Benefits of pulse GC therapy for canine PF
*Higher proportion of dogs achieve CR in 3 months
*Average dose of GC is lower overall
*Minimal AEs compared to conventional dosing
Feline PF treatments
*Oral glucocorticoids
*Pulse therapy not helpful in cats
*Apoquel (1 mg/kg BID tapered to 0.5mg/kg BID)
+/-
*Cyclosporine
*Chlorambucil
Pemphigus vulgaris major autoantigen in humans
Mucosal form: DSG-3 only
Mucocutaneous form: DSG-3 + DSG-1
Pemphigus vulgaris major autoantigen in dogs
DSG-3
Pemphigus vulgaris major autoantigen in cats
Unknown
Which layer of haired skin/foot pad as the most DSG3
Stratum basale
Which layer of haired skin/foot pad has the most DSC1
Stratum granulosum, Stratum spinosum
What layer of buccal mucosa has highest amount of DSG 3?
Stratum basale
How does autoantigen IgG lead to blisters in AISBDs?
Fab region binds to autoantigen, which induces C1q component of complement system –> Complement-dependent cytotoxicity –> Blisters
T or F: acantholysis requires interaction between IgG and complement system
FALSE.
PF/PV only need Fab region of IgG to induce acantholysis. Do NOT need Fc region/complement interactions
Mechanisms of acantholysis (3)
1) Steric hinderance
2) Desmoglein internalization and depletion
3) Signaling pathway interfering with cell adhesion
Mechanism of steric hinderance –> acantholysis
Binding of auto-Ab prevents bonding of desmoglein on same cell AND desmosomes between 2 cells
Mechanism of desmoglein depletion –> acantholysis
Binding of auto-Ab inhibits desmosome assembly
Also affects CLUSTERING of desmoglein, so it can’t function appropriately
When desmoglein is clustered (and nonfunctional), the desmosome is endocytosed and recycled –> depletion
Mechanism of signal transduction –> acantholysis
Auto-Ab affects the signal transduction pathway is affected. Leading to steric hinderance and desmoglein depletion
*Overexpression of c-myc in PV dogs interferes with signaling cascade needed for DSG-3 expression
Function of c-myc
Proto-oncogene
*Induces proliferation, transformation, and apoptosis
*Over expressed in canine PV
Clinical lesions of canine PV
*Erosions/ulcerations
*Mucous membranes +/- MC junctions involved
*Nail exclusive form (n=2), w/ onychomadesis
*Footpad only form (n=1)
Histopath of PV
Suprabasilar cleft w/tombstone appearance of basal keratinocytes
Treatment for canine PV
BEST FOR CR: GC + aza
*Apoquel 0.5mg/kg BID, CR in 6w
*GC, AZA, CsA, heparin, doxycycline
Diseases of pemphigoid complex
*MMP
*EBA
*BP
Most common AISBD in dogs
MMP > EBA > BP
Autoantigen for EBA
Type VII collagen (NC1 domain)
Lamina densa, anchoring fibrils
Autoantigen for BP
*BP180 (Collagen 17)
>
*BP230 (BPAG1e)
Autoantigen for MMP in dogs
*BP180 (Collagen 17, NC16A domain)
*BP230 (BPAG1e)
*Laminin 332
Pathogenesis of blister formation in AISBD
*Activation of complement system
Binding of autoantibodies –> antigen-antibody complex formation –> activation of complement pathway
3 Pathways for Complement Activation
1) Classical pathway (initiated by antigen-antibody complexes)
2) Lectin pathway (binding to mannose residues on cell or pathogen surfaces)
3) Alternative pathway (activated by spontaneous hydrolysis of C3 or via classical/lectin pathways)
Mechanism of classical complement pathway
*C1q binds to Ab-Ag complex
*Complement cascade activated
*Results in anaphylatoxins (C3a, C5a), opsonization (C3b), and MAC formation (C5b)
Which type of complement cascade activation occurs in AISBDs?
Classical complement pathway (via C3a, C5a)
What factors are released by inflammatory cells that lead to blister formation in AISBDs?
*Neutrophil elastase
*MMP-9
*ROS
Clinical features of AISBDs
*Vesicles/bullae
*Ulcerations
*Crust
*Depigmentation/scarring if chronic
Histopath for AISBDs
*Subepidermal cleft on histopath
*intact vesicles, ulcers
Which AISBD is mucosal/MC dominant with minimal skin lesions
MMP
Which AISBD is haired skin only
BP
EBA clinical features
*Young dogs (1-2 yrs old)
*Great Danes
*Severe systemic signs (fever, lymphadenopathy, lethargy, anorexia)
Treatment AISBDs
*Chronic relapsing course
*MMP:
-Doxycycline/ niacinamide
-Oral GC + AZA/CsA/Dapson
*EBA:
-Oral GC +/- AZA, colchicine
*Other AISBD:
-Oclactinib
-Oral GC + MMF
Which distribution of canine PF is more often pruritic?
Truncal (>60%)
But median pVAS of truncal and facial are similar. Similar in cats
What is the desmoglein compensation theory
When only one desmoglein molecule is “destroyed” by anti-DSG-3 AA, the other desmoglein takes over all the adhesion responsibility
(aka, why only MM affected in PV, even though DSG-3 is also present in skin in low amounts. BC DSG-1 can hold skin together).
Which non-DSG autoantibodies can contribute to blister formation in PV?
*Acetylcholine receptors
*Soluble Fas ligands
*Mitochondrial proteins
*E-cadherin
T or F: A PV affecting only the claws has been reported
True
T or F: PV affecting only the footpads has been reported
True.
Sloughing of footpads
CsA at 4 mg/kg/d and vitamin E was successful in inducing CR of which pemphigus/pemphigoid disease
PV canine
Most commonly affected body sites: MMP
Gingiva, hard palate
> > periocular, perioral, nasal planum, anogenital. Less likely haired skin
Body regions EBA
Oral cavity, glaborous skin (axillae, groin), footpads
Is footpad involvement more common in canine BP or EBA
EBA
Which AISBDs do cats have
*BP (2 cases)
*MMP (1 case)
Which species has a familial acantholysis; similar to acantholytic epidermolysis bullosa in humans?
Angus calves
Which species has a hereditary suprabasal acantholytic mechanobullous dermatosis; similar to acantholytic epidermolysis bullosa in humans?
Buffaloes
2 diseases that target DSG3 in dogs
*Pemphigus vulgaris
*Paraneoplastic pemphigus
Targets for mucocutaneous pemphigus vulgaris
DSG1, DSG3
Pemphigus vegetans target
DSG1
Perioral, perianal, skin folds
Bacteria that causes Exudative Epidermitis in puglets
Staphylococcus hyicus
What is the virulence factor and target in Exudative Epidermitis?
*Exfoliatin toxin
*DSG-1
3 general etiologies of acantholytic diseases
*Genetic
*Autoimmune
*Proteolytic (bacteria, fungal)
Acantholytic epidermolysis bullosa simplex in Angus cattle and Murrah buffalo: clinical lesions
Erosions, ulcers on pressure points of limbs, + tail. + Oral cavity + hoof sloughing
Prognosis of Acantholytic epidermolysis bullosa simplex in Angus cattle and Murrah buffalo
Lethal
Level of split for Acantholytic epidermolysis bullosa simplex in Angus cattle and Murrah buffalo
Suprabasilar + intrabasilar acantholysis
ABSENT DESMOSOMES
Protein/Gene mutated for Darier diseases
SERCA2 (? Disproven, ATP2A2
Protein/Gene mutated for Hailey Hailey disease
SPCA1, ATP2C1
Age of onset for Darier, Hailey Hailey
<2 months for canines
Puberty for humans
Clinical lesions Darier disease
Hyperplastic, scaly/greasey papules and plaques on head & lateral limbs
Clinical lesions Hailey Hailey disease
Vesicular lesions –> crusts, scaling on flexural surfaces
Histopath Darier Disease
*Suprabasilar acantholysis
*Corps ronds/ round bodies = dyskeratotic keratinocytes
*Basal cell vacuolation
*Decreased lateral desmosome adhesion
*Separation of keratin filaments from desmosomes –> Circular accumulation of keratin around nucleus, “perinuclear keratin rings”
Etiology Darier Disease, Hailey Hailey disease
*2’ impaired desmosome function (Cadherins need Ca to function) vs abnormal epidermal differentiation (abnormal Ca = more time in cell cycle, more mutations)
*Altered intracellular calcium homeostasis
Disease with “corps ronds”
Darier disease
= dyskeratotic keratinocytes
Hailey Hailey disease histopath
*Suprabasilar acanthylosis
*Separation of keratin filaments from desmosomes –> perinuclear keratin rings
Which level of epidermis are corps ronds present in Darier Disease
Stratum spinosum
Parakeratotic stratum corneum: “grains”
Breeds predisposed to pemphigus vulgaris
*German Shepherd dog
*Collies
Where are DSG1, DSG2, plakoglobin and desmoplakins in dog with Darier disease?
Cytoplasm. NOT at cell membrane
Sex predisposed to pemphigus vulgaris
*Males
Which type of antibody against DSG3 can be found in circulation in dogs with pemphigus vulgaris
IgG4
(Also IgG4 in PF)
Histopath of paraneoplastic pemphigus
*Suprabasilar acantholysis
*Apoptotic keratinocytes w/satellitosis
PV + EM = paraneoplastic pemhigus
Target of paraneoplastic pemphigus
*DSG3
*Plakins (envoplakin, periplakin)
Dog breed w/ Pemphigus Vegetans (1 case)
Greater Swiss Mountain Dog
Histopath finding of Pemphigus Vegetans
*Epidermal hyperplasia
*Neutrophilic, eosinophilic acantholytic pustules in MULTIPLE LEVELS
-Suprabasal
-Intrasponous
-Subcorneal
Clinical lesions of pemphigus erythematosus (PE)
*Superficial pustular lesions (like PF)
*Deep nasal ulcers (like DLE)
Trichophyton proteases that may cause proteolytic acantholysis
*Substilisins
*Fungalysin metalloproteases
*Di-peptyl-peptidases
*Amino- or caroboxy- peptidases
Histopath of superficial pustular dermatophytosis
*Neutrophilic subcorneal pustules w/acantholytic keratinocytes
*Lymphocyte-rich interface dermatitis
*Dermatophyte hyphae in stratum corneum
*MINIMAL DERMATOPHYTE HAIR INVASION (dif than classical dermatophytosis)
3 Staphylococcus species that can cause Exudative epidermitis in piglets
1) Staphylococcus hyicus
2) Staphylococcus chromogenes
3) Staphylococcus sciuri
Where do clinical lesions of Exudative epidermitis begin?
Face (acute or peracute) + Coronary bands, heels
Generalized erythema, brown exudate, crusting over shallow erosions
Which toxins are implicated in Exudative epidermitis
Exfoliatin toxins
*ExhA
*ExhB
*ExhC
*ExhD
*SHETA
*SHETB
–> Digest DSG1
Target of Exudative epidermitis
DSG1
Bacteria implicated in bullous impetigo and exfoliative superficial pyoderma in dogs
Staphylococcus pseudintermedius
Age of dogs overrepresented for Bullous Impetigo
Puppies or immunosuppresse old dogs
Clinical lesions in Bullous Impetigo
Large non-follicular pustules –> rupture into yellow crusts, epidermal collarettes
USUALLY NO PAPULES
Location in epidermis of pustules of bullous impetigo
Subcorneal or Intragranular (like PF)
Neutrophilic w/AKs + Gram positive cocci
Superficial spreading pyoderma clinical lesions
Rapidly expanding epidermal collarettes, polycyclic pattern
Centrifugal peeling of stratum ocrneum
Staphylococcal scalded skin syndrome clinical lesions
Acute onset regional/generalized erythema with large sheets of scale
Toxin associated with Exfoliative Superficial Pyoderma
Exfoliatin toxin
*SIET
DIFFERENT than exfoliatin toxins of Staph aureus and hyicus.
T or F: If you inject ETA, ETB or ETD from S aureus into a dog, they will develop acantholytic epidermal pustules
FALSE.
Each exfoliatin toxin is species specific
Idiopathic linear pustular acantholytic dermatosis in 2 dogs, clinical lesions
Linear coalescing papules, pustules, crusts with peripheral erythema on face, limbs
Idiopathic linear pustular acantholytic dermatosis in 2 dogs, treatment
Responsive to high dose medrol in both dogs. Recurrence in 1 dog.
Infectious etiologies were ruled out. Each dog only had a SINGLE lesion!
Dog Breeds overrepresented for Pemphigus foliaceus
*Akita
*Chow Chows
(+others, but varies based on the study/geographic region)
Horse Breeds overrepresented for Pemphigus foliaceus
*Appaloosa
Unusual clinical sign in horses with Pemphigus foliaceus
Ventral edema
Diseases encompassed by Panepidermal Pustular Pemphigus
Pemphigus vegetans (DSG1) + Pemphigus erythematosus (unknown target)
Breed for Darier disease
Irish Setter
(Also shih tzu)
Genetic acantholytic dermatoses (acantholytic EBS, Darier): desmosomes on electron microscopy
Rare to absent
Keratin intermediate filaments often detached from desmosomes, with cytoplasmic aggregation
Which types of pemphigus have a positive Direct Nikolskiy sign
Pemphigus vulgaris
Paraneoplastic pemphigus
(unknown if pemphigus vegetans does)
IgA pemphigus targets, layers in epidermis affected
IgA against DSC1, DSC3
Affects spinous and granular layers of epidermis
Breed pemphigus erythematosus
GSD, Sheltie, Collie
Immune response causing pemphigus vulgaris
T cell-mediated component: Th1 via IFNg
Also, Th2 cytokines (IL-4) promote B cell proliferation, antibody production, antibody class switching
Th17 also involved
Linear IgA Dermatosis target, location in BMZ
Collagen 17
Lamina densa
Clinical sign of linear IgA dermatosis
Eosinophilic papules, pustules
Pruritic
Dachshunds
Target of MMP in cats
Laminin 5
(usually collagen 17 CN16A domain in dogs)
JEBA target
Laminin 332
Which cells are implicated in bullous pemhigoid
Treg dysfunction
Allows Th2 to make IL-4, which stimulates B cell antibody production
Th17 recruits neutrophils