Lecture 3 11/27/25 Flashcards
What are the responses of the epidermis to injury?
-changes in growth or differentiation
-changes in fluid balance or cell adhesion
-inflammation
-alterations in epidermal pigment
What are the potential alterations in epidermal growth/differentiation?
-hyperkeratosis
-epidermal hyperplasia
-dysplasia
-atrophy
-dyskeratosis/apoptosis/necrosis
What are the characteristics of hyperkeratosis?
-increased thickness of stratum corneum/keratin layer
-can be a non-specific reaction to chronic stimuli
What are the conditions that cause orthokeratotic (lacking nuclei) hyperkeratosis?
-seborrhea
-ichthyosis
-vitamin A deficiency
What are the conditions that cause parakeratotic (retaining nuclei) hyperkeratosis?
-zinc-responsive dermatosis
-superficial necrolytic dermatitis
What are the characteristics of epidermal hyperplasia?
-increased thickness of epidermis due to increased number of cells
-typically in stratum spinosum; termed acanthosis
-non-specific response to chronic stimuli
What are the characteristics of rete pegs?
-down-growths of epidermis into dermis
-normal in areas of high friction
-seen in areas with chronic irritation (abnormal)
What are the characteristics of epidermal dysplasia?
-abnormal development of the epidermis
-disorganization of any of the epidermal layers
-typically occurs in basal cells
-often a pre-neoplastic lesion
What is epidermal atrophy?
decrease in the number and size of cells within the epidermis
What are the possible causes of epidermal atrophy?
-hyperadrenocorticism
-partial ischemia
-severe malnutrition
What are the characteristics of dyskeratosis, apoptosis, and necrosis?
-distinct pathogenesis that are histologically identical
-cells become shrunken and hypereosinophilic
Which diseases have dyskeratosis/apoptosis/necrosis confined to the basal layer?
-discoid lupus
-mucocutaneous pyoderma
Which disease has dyskeratosis/apoptosis/necrosis in multifocal spots throughout all layers?
erythema multiforme
Which diseases have dyskeratosis/apoptosis/necrosis in a diffuse pattern/full thickness?
-toxic epidermal necrolysis
-thermal injury
What are the potential consequences of alterations in the epidermal adhesion molecules?
-edema/fluid buildup
-acantholysis/loss of cell adhesion
What are the mechanisms of vesicle formation?
-widening of intercellular spaces due to worsening edema; causes spongiosis
-loss of cells due to worsening edema; causes ballooning degeneration/intra-cellular edema
-loss of intercellular junctions resulting in separation of cells; causes acantholysis
Which disease processes can lead to acantholytic cells?
-immune-mediated processes
-neutrophilic enzyme destruction
How do acantholytic cells differ from apoptotic cells on cytology?
-acantholytic cells are typically disassociated from other cells
-apoptotic cells are not disassociated from other cells
How does vesicle location and appearance within the epidermis differ with different pemphigus types?
-pemphigus folicaceous: vesicle develops “between” epidermis and stratum corneum and contains acantholytic cells
-pemphigus vulgaris: vesicle develops “between” epidermis and dermis and contains acantholytic cells
-bullous pemphigoid/thermal burns: vesicle develops “between” epidermis and dermis with no acantholytic cells
What is exocytosis?
inflammatory cells “walking” through the epidermis
What is a pustule?
accumulation of cells in the epidermis that have moved via exocytosis
Which cells accumulate in a pustule and when?
-neutrophils: bacterial infection, pemphigus
-eosinophils: ectoparasites, pemphigus
When do crusts form?
as pustules dry up and are pushed off by the hyperplastic epidermis
What are the potential alterations in epidermal pigmentation?
-hyperpigmentation
-pigmentary incontinence
What are the characteristics of hyperpigmentation?
-most commonly due to increased production of melanin by existing melanocytes
-pigment may be in all layers of epidermis
-can occur with chronic inflammatory disease and endocrine dermatoses
What is the less common cause of hyperpigmentation?
proliferation of melanocytes
What are the characteristics of pigmentary incontinence?
-loss of melanin from the pigmented cells in the basal layer
-non-specific change associated with inflammation
-seen with discoid lupus, mucocutaneous pyoderma, and uveodermatologic syndrome
What are the responses of the dermis to injury?
-alterations in growth
-collagen degradation
-dermal deposits
-inflammation in the dermis
What are the characteristics of dermal atrophy?
-decrease in the quantity of collagen fibrils and fibroblasts in the dermis
-seen in hyperadrenocorticism
What are the characteristics of collagen degradation?
-hyper-eosinophilic “flame figures”
-degradation is surrounded by eosinophils and major basic protein
-seen with eosinophilic diseases
Which eosinophilic diseases can lead to collagen degradation?
-feline eosinophilic granuloma complex
-canine eosinophilic granulomas
-equine nodular necrobiosis
-habronemiasis
-mast cell tumors
What are dermal deposits?
deposits within the dermis that lead to expanding and separating of normal skin
When are dermal deposits seen?
-shar peis (normal for breed)
-hypothyroidism
What is calcinosis cutis?
-mineralization of collagen that occurs with no pattern
-seen with hyperadrenocorticism
What is calcinosis circumscripta?
mineralization of collagen that is deposited in nodules
What are the different patterns of dermatitis?
-perivascular
-vasculitis
-interface
-nodular/diffuse
What are the characteristics of perivascular dermatitis?
-inflammatory cells are centered around blood vessels
-usually superficial
-not specific
What are the characteristics of vasculitis dermatitis?
-inflammation targets walls of blood vessels
-consists of damage to vessel wall, fibrin deposition, thrombosis, and hemorrhage
-results in ischemia
-seen in immune-mediated disease and sepsis
What are the characteristics of interface dermatitis?
-superficial dermal inflammation
-inflammatory cells surround dermo-epidermal junction
-damage to basal cells occurs
-obscuring of dermo-epidermal junction
-pigmentary incontinence
What is lichenoid?
interface dermatitis in which there is just a band beneath the dermis with no obscuring
What are the characteristics of nodular to diffuse dermatitis?
-usually infectious
-pathogenesis varies with type of inflammatory cell present
-can be sterile
How do the different inflammatory cells indicate the pathogenesis of nodular to diffuse dermatitis?
-neutrophils: bacterial
-granulomatous: fungi or foreign body
eosinophils: parasites
-lymphocytes and plasma cells: non-specific
What are the responses of the adnexa to injury?
-alterations in growth
-inflammation of the adnexa
What can lead to atrophy of the adnexa?
-endocrine disease
-ischemia
What can lead to hypertrophy of the adnexa?
chronic irritation
What are the characteristics of folliculitis?
-usually infectious
-can be immune-mediated
-progresses to furunculosis
What are the characteristics of furunculosis?
-inflammation associated with follicular rupture
-free keratin/hairs act as foreign bodies in dermis
-leads to granulomatous inflammation
What is sebaceous adenitis?
immune-mediated reaction targeting the sebaceous glands that can result in a total loss of the glands
What are the changes in growth seen in the panniculus?
-atrophy due to chronic negative energy balance
-hypertrophy due to obesity
What are the potential causes of panniculitis?
-infectious
-immune-mediated
-nutritional
-pancreatic disease
-idiopathic
-vaccine/injection site reaction
-trauma
