Immune Function and Immune-Mediated Diseases 9% Flashcards
What are cross-reactive carbohydrate determinants (i.e. CCD’s)?
IgE-binding carbohydrate structures common to plant and insect species; in people, they are thought to be clinically irrelevant but have the potential to confound serologic IgE test intepretation.
Ischemic dermatopathy is a general designation for the following 5 vasculopathic syndromes that a united by similar clinical and histopathologic features.
1) Canine familial dermatomyositis
2) Dogs with juvenile-onset ischemic dermatopathy that is identical to dermatomyositis but without proven breed predilection/familial predisposition
3) Postrabies vaccination panniculits
4) Generalized vaccine-induced ischemic dermatopathy (GVIID)
5) Generalized idiopathic ischemic dermatopathy (GIID)
The 5 vasculopathic syndromes that make up “ischemic dermatopathy” are united by what histologic feature?
Cell-poor vasculitis
What are the clinical features of ischemic dermatopathy?
Alopecia, crusting, post-inflammatory, mottled pigmentary change, erosion, ulceration, scarring. Rare, transient papules, pustules and vesicles, claw dystrophy, claw sloughing
What body sites are affected with ischemic dermatopathy?
Over bony prominences, muzzle, perioribital region, personal, forum, distal phalanges, distal extremities, pressure points, pinnae (especially tips), pinnal folds, claw folds, tip of the tail
What are the primary histologic findings of ischemic dermatopathy?
- scattered degeneration (vacuolated or apoptotic) of basal cells; follicular epithelium to isthmus more affected than basal epidermis
- Very mild, diffuse dermal inflammation that loosely encircles follicles; lymphocytes and histiocytes predominate
- Increased prominence of the connective tissue surrounding the external root sheath of the atrophic hair follicle
- Diffuse pallor of the dermis; pale-staining, smudged collagen that has lost fibrillar character
- Hair follicles are severe atrophied (i.e. “faded”)
What is canine familial dermatomyositis?
A vasculopathic syndrome reserved for those dogs with clinical and histopathologic evidence of a juvenile onset heritable inflammatory disease affecting the skin and muscle
What may trigger a relapse of ischemic dermatopathy?
Photo-aggravation, trauma and estrus
IN CASES OF ISCHEMIC DERMATOPATHY, MAKE SURE TO CHECK
- FOR A VACCINE SITE
- PINNAL MARGINS AND PINNAE
- TAIL TIP
- CLAWS AND CLAW FOLDS
- PAW PADS
- FACE
What breeds seem to be at higher risk for postrabies vaccination panniculitis?
long haired toy or miniature breeds seem to be at greater risk but it can happen to any breed.
What breeds appear predisposed to developing DLE?
Collie, Shetland Sheepdog, German Shepherd (especially White German Shepherds), Siberian Husky
What are the histopathologic features of discoid lupus erythematosus?
- Basal cell degeneration, both apoptotic and vacuolar, creates an irregular and indistinct dermal-epidermal junction that is obscured by interface inflammation
- Secondary erosion/ulceration and superficial pustulation and crusting are observed in severe cases
- Moderate acanthosis
- Epidermal atrophy may be present; the basement membrane may be markedly thickened in some cases
- Dermis usually has a lichenoid/band-like mild to moderate inflammatory infiltrate that includes lymphocytes/macrophages/plasma cells and neutrophils
- Inflammation often obscures the dermal-epidermal junction and best termed “lichenoid-interface”
- Pigmentary incontinence
- There can be a zone of superficial laminar hypocellularity with/without laminar fibrosis termed a “Grenz zone” subtended by a deeper zone of lichenoid inflammation
What are the cutaneous manifestations of systemic lupus erythematosus (which can occur in < 20 % of dogs with SLE)?
Erythema, scaling, crusting, depigmentation, alopecia, bullae –> ulcers involving the skin, mucocutaneous junctions and mucous membranes
- Generalized exfoliative dermatitis, ulcers of the pawpads, panniculitis and lesions closely mimicking DLE
- Face, ears and distal extemities are common sites of involvement
What are the histologic features of cutaneous lesions of SLE?
- Basal cell vacuolation and apoptosis of basal cells occurs, leading to dermal-epidermal separation and ulceration; superficial hair follicles to the level of the isthmus may be similarly affected
- Vasculitis may occur
- Other forms of lupus erythematosus and erythema multiforme are the principal differential diagnosis; lupid drug reactions are essentially identical in appearance
- DLE tends to have more intense band-like dermal infiltrate and less severe basal degeneration than SLE; EM shows more prominent individual keratinocyte necrosis at all levels of the epidermis
What are the histologic features of pemphigus erythematosus?
- Superficial pustulation as seen in pemphigus foliaceus but has an interface component
- A pemphigus-lupus crossover disease
- Superficial inflammation composed of lymphocytes, histiocytes and plasma cells that obscures the dermal-epidermal interface, resembling DLE
- Mild to moderate pigmentary incontinence
- Using immunofluorescence or IHC, deposition of immunoglobulin along the basement membrane in addition to the typical intercellular deposition of PF
Erythema multiforme
Believed to be a host-specific T cell mediated hypersensitivity in which the cellular immune response is directed against various keratinocyte-associated antigens, including those associated with drug administration, infection, neoplasia, and connective tissue disease. Lymphocytes bind to the antigenically altered keratinocytes and trigger cell death via apoptosis.
Define erythema multiforme minor and erythema multiforme major
Erythema multiforme minor: Target lesions, no more than one mucosal surface affected and less than 10% of the body surface area affected
EM major: more than one mucosal surface affected, 10 - 50 % of the body surface affected, with less than 10% epithelial detachment.
Stevens-Johson syndrome: severe EM with >50% body surface affected, with epithelial detachment ranging between 10-30%.
Toxic epidermal necrolysis: separate syndrome, over 30% of epidermal detachment
SJS-TEN overlap: features of both TEN and SJS with 10-30% epithelial detachment
What are some triggers for Erythema multiforme in small animals?
- Drug hypersensitivity (TMS, penicillins, cephalosporins)
- Neoplasia
- Infection
- Dyes, preservatives, stabilizers in pet foods may act as”drugs”
What is the most common cause of EM in humans?
Herpesviral infection
What is the distribution of lesions in EM?
Ventrum (groin and axillae), oral cavity, mucocutaneous junctions, concave pinnae and pawpads
Describe the clinical lesions of erythema multiforme
- acute onset of erythematous, annular macules, elevated circular plaques and papules, that progress rapidly into partially symmetrical patterns
- Early lesions may appear urticarial
- Crusting becomes more noticeable as lesions evolve
- Some lesions become targetoi with multiple concentric circular zones of erythema, blanching and exfoliation
- Adjacent lesions may coalesce to form distinctive arciform-serpiginous patterns
- In more severe forms, ulceration can become severe
- Old dog EM: exudative and proliferative lesions and predominately involve the face and ears
- Mucosal lesions: vesicles and bullae –> ulcers
What are the histologic features of erythema multiforme?
- Apoptosis with lymphocyte satellitosis
- Interface dermatitis
- Lesions extend to superficial hair follicles
- Lymphocytes and macrophages are grouped along the dermal-epidermal junction and partially obscure it
- Dermal inflammation is usually mild but can approach band-like
- There is vacuolation of the basement membrane zone , often with a bubbling pattern, individual basal cell apoptosis may be present
- In EM, apoptosis is more prominent and seen in all levels of the epidermis; lupus has apoptosis that is typically distributed to the basal cell layer ; feline thymoma associated exfoliative dermaitits has less severe transepidermal apoptosis than EM.
Where are mast cells found in highest numbers?
Skin, lung, gastrointestinal tract
What are the basic function of mast cells?
Antigen-specific role in the development of allergic inflammation, innate defense against helminths and bacteria, wound healing