SAD - Chapter 16 - Environmental Skin Dz

Question 1

Which is more erythemogenic: UVA or UVB?

Answer 1

UVB – known as the sunburn or erythema spectrum

Question 2

Which penetrates deeper into the skin: UVA or UVB?

Answer 2

UVA – spectrum associated with photosensitivity reactions

Question 3

What are natural barriers to UV light damage?

Answer 3

stratum corneum, melanin, blood, carotenes

Question 4

_____ is the classic sunburn reaction and is a dose-related response to light exposure.

Answer 4

Phototoxicity

Question 5

_____ 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.

Answer 5

Photosensitivity

Question 6

T/F: Solar dermatitis is purely a phototoxic reaction.

Answer 6

True - sunburn type reaction

Question 7

Histopathological features of solar dermatitis

Answer 7

clusters of vacuolated keratinocytes in the superficial epidermis (sun-burn cells), apoptotic keratinocytes, vascular dilatation and leakage

Question 8

How quickly do apoptotic keratinocytes occur after UVA exposure? By what mechanism is apoptosis induced?

Answer 8

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

Question 9

What are the key features of nasal solar dermatitis?

Answer 9

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

Question 10

What are some of the long-term consequences of nasal solar dermatitis?

Answer 10

scarring, squamous cell carcinoma

Question 11

DDX for nasal solar dermatitis

Answer 11

DLE, SLE, dermatomyositis, epidermolysis bullosa, pemphigus foliaceus, pemphigus erythematosus, drug reaction, infectious folliculitis, neoplasia, vasculitis, granulomatous diseases

Question 12

Histopathological features of nasal solar dermatitis

Answer 12

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

Question 13

What stain can help to highlight solar elastosis (basophilic degeneration of elastin)?

Answer 13

Verhoeff stain

Question 14

Feline solar dermatitis is most common in what color of cats? What areas are most affected?

Answer 14

white cats – ears&raquo_space; eyelids, nose, lips

Question 15

DDX for feline solar dermatitis affecting the pinna

Answer 15

dermatophytosis, notoedric mange, fight wounds, vasculitis, frostbite, cryoglobulinemia, DLE, SLE, PE, PF

Question 16

Histopathological features of feline solar dermatitis

Answer 16

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

Question 17

Treatments for feline solar dermatitis

Answer 17

avoidance of sun; sunscreen; Beta-carotene, canthaxanthin; retinoic acids; superficial irradiation with strontium probe; imiquimod; surgical removal

Question 18

What breeds are predisposed to truncal solar dermatitis?

Answer 18

dalmatian, American Staffordshire terrier, German shorthaired pointers, white boxers, whippets, beagles, and white bull terriers

Question 19

Describe the progression of lesions of truncal solar dermatitis

Answer 19

sunburn (erythema, scale) –> actinic folliculitis, actinic follicular cyst formation, dermal fibrosis –> erosions, ulceration, crusting, comedones –> necrosis, fistulae, scarring –> squamous cell carcinoma

Question 20

What is different in the areas of the body that are affected by solar dermatitis vs. photosensitivity?

Answer 20

Photosensitivity can occur in well-haired regions of the body; solar dermatitis affects lightly haired areas

Question 21

UV light may induce or exacerbate the lesions of what underlying skin conditions?

Answer 21

DLE, SLE, pemphigus foliaceous/erythematosus, pemphigoid

Question 22

What layers of the skin are affected with superficial burns?

Answer 22

epidermis

Question 23

What layers of the skin are affected with partial-thickness burns?

Answer 23

epidermis and superficial dermis

Question 24

What layers of the skin are affected with full-thickness burns?

Answer 24

epidermis, dermis, adnexa

Question 25

What organisms colonize burn wounds?

Answer 25

initially -- gram positive, 3-5 days later --> gram-negative flora (P. aeruginosa)

Question 26

What is a diagnostic histopathological feature of electric burns?

Answer 26

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")

Question 27

T/F: Systemic antibiotics are useful to prevent burn wound infection.

Answer 27

False - not effective and may allow invasion by resistant organisms

Question 28

Histopathological features of radiant burns

Answer 28

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**

Question 29

How long after radiation therapy do skin changes appear? Why?

Answer 29

2-3 weeks later; treatment stops the mitotic activity of the epidermis, melanocytes, hair follicles, sebaceous glands

Question 30

What is the pattern of progression with radiation burns?

Answer 30

scaly/alopecic --> exudation and ulceration

Question 31

Why should an animal have skin testing before administration of antivenin?

Answer 31

contains horse serum --> can lead to anaphylaxis

Question 32

T/F: Antibiotics should be administered after a snake bite.

Answer 32

True -- snake bites are contaminated with oral flora, which often includes Pseudomonas spp. And Clostridium tetani

Question 33

What analgesics should be avoided after a snake bite? Why?

Answer 33

morphine and NSAIDs --> might result in histamine release or predispose to clotting disorders

Question 34

T/F: Pit viper bites always inject venom.

Answer 34

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

Question 35

Cutaneous lesions of snake bites with venom

Answer 35

rapid progression of edema (obliterates the fang marks), pain, hemorrhage --> ecchymosis and discoloration --> necrosis and sloughing

Question 36

T/F: Antivenin should be given to all animals with a snake bite.

Answer 36

False -- for maximum efficacy, needs to be administered within 4 hours of the bite, given 8 hours after a bite --> little value

Question 37

What is Hordeum jubatum?

Answer 37

foxtail

Question 38

What is Arctium spp.?

Answer 38

burdock

Question 39

Myospherulosis

Answer 39

rare granulomatous reaction thought to be due to the interactioin of ointments, antibiotics, endogenous fat, oily contents of cysts with erythrocytes

Question 40

T/F: Skin lesions are not seen in acute thallium intoxication.

Answer 40

TRUE

Question 41

Clinical signs of chronic thallium poisoning

Answer 41

hyperemic mucous membranes, mild to moderate GI signs, skin lesions of erythema & alopecia, hyperkeratosis and ulceration of footpads

Question 42

Hygroma

Answer 42

false or acquired bursa that develops subcutaneously over bony prominences

Question 43

Histopathological features of hygromas

Answer 43

cystic spaces surrounded by dense walls of granulation tissue, inner layer of which is a flattened layer of fibroblasts