SAD - Chapter 16 - Environmental Skin Dz Flashcards
Which is more erythemogenic: UVA or UVB?
UVB – known as the sunburn or erythema spectrum
Which penetrates deeper into the skin: UVA or UVB?
UVA – spectrum associated with photosensitivity reactions
What are natural barriers to UV light damage?
stratum corneum, melanin, blood, carotenes
_____ is the classic sunburn reaction and is a dose-related response to light exposure.
Phototoxicity
_____ occurs when the skin has increased susceptibility to the damaging effects of UV light because of the production, ingestion, injection of, or contact with a photodynamic agent.
Photosensitivity
T/F: Solar dermatitis is purely a phototoxic reaction.
True - sunburn type reaction
Histopathological features of solar dermatitis
clusters of vacuolated keratinocytes in the superficial epidermis (sun-burn cells), apoptotic keratinocytes, vascular dilatation and leakage
How quickly do apoptotic keratinocytes occur after UVA exposure? By what mechanism is apoptosis induced?
biphasic apoptosis – seen within 4 hours due to UVA’s direct damaging effect on the cell membrane; seen 24 hours after exposure – due to DNA alteration
What are the key features of nasal solar dermatitis?
restriction of lesions to sun-exposed, nonpigmented, sparsely haired skin; onset of signs after solar exposure; absence of skin lesions in the affected area before the condition began; complete resolution with removal from sunlight
What are some of the long-term consequences of nasal solar dermatitis?
scarring, squamous cell carcinoma
DDX for nasal solar dermatitis
DLE, SLE, dermatomyositis, epidermolysis bullosa, pemphigus foliaceus, pemphigus erythematosus, drug reaction, infectious folliculitis, neoplasia, vasculitis, granulomatous diseases
Histopathological features of nasal solar dermatitis
early depigmented areas of nose – fewer melanocytes and less melanin pigment; after exposure to solar radiation –> epidermal hyperplasia with intraepidermal edema; vacuolated (sunburn cells) and apoptotic keratinocytes; superficial perivascular dermatitis, vascular dilatation; solar elastosis (basophilic degeneration of elastin); bandlike superficial dermal fibrosis
What stain can help to highlight solar elastosis (basophilic degeneration of elastin)?
Verhoeff stain
Feline solar dermatitis is most common in what color of cats? What areas are most affected?
white cats – ears»_space; eyelids, nose, lips
DDX for feline solar dermatitis affecting the pinna
dermatophytosis, notoedric mange, fight wounds, vasculitis, frostbite, cryoglobulinemia, DLE, SLE, PE, PF
Histopathological features of feline solar dermatitis
superficial perivascular dermatitis (spongiotic, hyperplastic changes); vacuolated (sunburn cells) or apoptotic keratinocytes; solar elastosis in the superfical dermal connective tissue; with SCC –> epidermal surface becomes ulcerated and the dermis is invaded by nests of polyhedral epithelial tumor cells
Treatments for feline solar dermatitis
avoidance of sun; sunscreen; Beta-carotene, canthaxanthin; retinoic acids; superficial irradiation with strontium probe; imiquimod; surgical removal
What breeds are predisposed to truncal solar dermatitis?
dalmatian, American Staffordshire terrier, German shorthaired pointers, white boxers, whippets, beagles, and white bull terriers
Describe the progression of lesions of truncal solar dermatitis
sunburn (erythema, scale) –> actinic folliculitis, actinic follicular cyst formation, dermal fibrosis –> erosions, ulceration, crusting, comedones –> necrosis, fistulae, scarring –> squamous cell carcinoma
What is different in the areas of the body that are affected by solar dermatitis vs. photosensitivity?
Photosensitivity can occur in well-haired regions of the body; solar dermatitis affects lightly haired areas
UV light may induce or exacerbate the lesions of what underlying skin conditions?
DLE, SLE, pemphigus foliaceous/erythematosus, pemphigoid
What layers of the skin are affected with superficial burns?
epidermis
What layers of the skin are affected with partial-thickness burns?
epidermis and superficial dermis
What layers of the skin are affected with full-thickness burns?
epidermis, dermis, adnexa
What organisms colonize burn wounds?
initially – gram positive, 3-5 days later –> gram-negative flora (P. aeruginosa)
What is a diagnostic histopathological feature of electric burns?
fringe of elongated degenerated cytoplasmic processes that protrudes from the lower end of the detached basal cells into the space separating the epidermis and the dermis; nuclei of the basal cells appear stretched in the same direction as the fringe of cytoplasmic processes (keratinocytes “standing at attention”)
T/F: Systemic antibiotics are useful to prevent burn wound infection.
False - not effective and may allow invasion by resistant organisms
Histopathological features of radiant burns
nonulcerated lesions – hyperplastic with surface and infundibular hyperkeratosis; keratinocyte atypia, karyomegaly, basaloid dysplasia; focal hydropic degeneration of basal cells and pigmentary incontinence; occasional apoptotic cells in suprabasilar layers; superficial dermal mucinosis; wavy eosinophilic elastin fibers in the superficial dermis
How long after radiation therapy do skin changes appear? Why?
2-3 weeks later; treatment stops the mitotic activity of the epidermis, melanocytes, hair follicles, sebaceous glands
What is the pattern of progression with radiation burns?
scaly/alopecic –> exudation and ulceration
Why should an animal have skin testing before administration of antivenin?
contains horse serum –> can lead to anaphylaxis
T/F: Antibiotics should be administered after a snake bite.
True – snake bites are contaminated with oral flora, which often includes Pseudomonas spp. And Clostridium tetani
What analgesics should be avoided after a snake bite? Why?
morphine and NSAIDs –> might result in histamine release or predispose to clotting disorders
T/F: Pit viper bites always inject venom.
False - 20-25% of pit viper bites can be dry; if no pain or swelling at the bite site occurs within 1.5 hours of the bite, no venoma was injected
Cutaneous lesions of snake bites with venom
rapid progression of edema (obliterates the fang marks), pain, hemorrhage –> ecchymosis and discoloration –> necrosis and sloughing
T/F: Antivenin should be given to all animals with a snake bite.
False – for maximum efficacy, needs to be administered within 4 hours of the bite, given 8 hours after a bite –> little value
What is Hordeum jubatum?
foxtail
What is Arctium spp.?
burdock
Myospherulosis
rare granulomatous reaction thought to be due to the interactioin of ointments, antibiotics, endogenous fat, oily contents of cysts with erythrocytes
T/F: Skin lesions are not seen in acute thallium intoxication.
TRUE
Clinical signs of chronic thallium poisoning
hyperemic mucous membranes, mild to moderate GI signs, skin lesions of erythema & alopecia, hyperkeratosis and ulceration of footpads
Hygroma
false or acquired bursa that develops subcutaneously over bony prominences
Histopathological features of hygromas
cystic spaces surrounded by dense walls of granulation tissue, inner layer of which is a flattened layer of fibroblasts
