Special pathology - dermatology Flashcards
The skin provides a protective barrier against? (4)
fluid loss, microbiologic agents, chemicals, and physical injury
A myriad of exogenous and endogenous factors influence the skin how?
gross and microscopic appearance of the skin.
Because the skin can respond to these factors in only a limited number of ways,
different skin disorders may have a similar histologic appearance!
A pathologic skin pattern description consists of two parts:
a component of the skin (e.g., epidermis) +
a histologic reaction of that component to injury
(e.g., hyperkeratosis)
= pattern (hyperkeratotic diseases of the epidermis).
pansteatitis
or yellow fat disease, is a physiological condition in which the body fat becomes inflamed.
callus
Thick, firm, hyperkeratotic, hairless plaque with increased skin folds, wrinkles, or fissures.
In haired skin, follicular plugging and comedones also may develop.
Example: Trauma over bony prominence such as elbow, sternum, or side of digit.
COMEDO (pl. COMEDONES)
Plug of stratum corneum and sebum within the lumen of a hair follicle that leads to follicular distention.
Examples: Canine solar (actinic) dermatosis, chin acne, Schnauzer comedo syndrome, hyperadrenocorticism, canine palmar and plantar interdigital cysts
CRUST
Dried exudate composed of various components, including fluid, blood, pustular debris, scale, or microorganisms on the skin surface.
Example: Chronic stage of pustular disease such as staphylococcal infection
CYST
Cavity lined by epithelium
filled with liquid or semisolid material
located in the dermis or subcutis;
may communicate with surface via a pore.
Examples: Follicular cyst, dermoid cyst, apocrine gland cyst
EPIDERMAL COLLARETTE
A thin layer of scale that expands peripherally and forms a ring (arrows).
Examples: Superficial bacterial infection, insect bite, fungal infection
EROSION
Partial-thickness loss of epidermis resulting in shallow, moist, glistening depression
(arrows).
Examples: Secondary to vesicle or pustule rupture or secondary to surface trauma
EXCORIATION
Shallow, vertically oriented linear break in skin surface (epidermis) (arrows)
Example: Abrasion or scratch
skin FISSURE
Deep, vertically oriented linear cleft or break (arrow) from the epidermis into the
dermis.
Examples: Pawpad fissure seen in superficial necrolytic dermatitis, or digital hyperkeratosis
LICHENIFICATION
Rough, thickened epidermis secondary to persistent rubbing, scratching, or irritation;
may have increased pigmentation.
Example: Chronic dermatitis
MACULE
Flat, circumscribed, nonpalpable area that is a change in the color of the skin, < 1 cm
in diameter.
Examples: Hemorrhage, vitiligo
NODULE
Elevated, often firm, circumscribed, solid palpable lesion ≥1 cm in diameter. Often
located in dermis or subcutis.
Examples: Bacterial or fungal infection, infectious or sterile granuloma
PAPULE
Elevated, firm, palpable, circumscribed area < 1 cm in diameter (arrows), but may
occur grouped together, may coalesce to form a plaque.
Examples: Insect bite, papilloma, superficial folliculitis
PLAQUE
Elevated, usually firm, flat-topped, circumscribed, palpable lesion ≥ 1 cm in diameter, may coalesce to form a larger lesion.
Examples: Calcinosis cutis, reactive histiocytosis, eosinophilic plaque
PUSTULE, EPIDERMAL
Circumscribed raised superficial accumulation of purulent fluid within the epidermis
(arrow).
Examples: Bacterial infection, pemphigus foliaceus
name 3 causes of skin scales
SCALE
Sheets of cornified cells that horizontally split and separate from underlying
epidermis as irregular, thick or thin, dry or oily fragments, may adhere to hairs.
Variations include silvery, powdery, greasy, gritty, and polygonal.
Examples: Cornification disorders, sebaceous adenitis, ichthyosis
Sebaceous adenitis is an
Sebaceous adenitis is an immune-mediated disorder in which an inflammatory process is directed against the sebaceous glands in the skin.
ULCER
Full-thickness loss of epidermis and basement membrane, and at least a portion of
the dermis with depression of the exposed surface. May extend into deeper tissue.
Examples: Ischemic lesions resulting from vasculitis, feline herpesvirus dermatitis, feline ulcerative dermatitis syndrome
VESICLE AND BULLA
Elevated, circumscribed, horizontal, fluid-filled lesions differentiated by size.Fluid may be
clear, tan, or red (hemorrhagic)
Vesicle: < 1 cm in diameter
Bulla: ≥ 1 cm in diameter (arrows)
Examples: Burn, viral infection
diff between a vesicle and a bulla
Vesicle: < 1 cm in diameter
Bulla: ≥ 1 cm in diameter
WHEAL
Elevated, irregular-shaped area of dermal edema; solid, usually transient, often pale
centrally with an erythematous rim (arrows)
Examples: Insect bites, urticaria, allergic reaction.
Dermatitis
nonspecific term used until the dermatologic history, clinical signs, and physical examination can more precisely define the problem.
Many skin diseases look alike and are differentiated by working through diagnostic flow charts and a process of elimination.
The most common dermatologic problems include: (8)
alopecia
erosions and ulcerations
nodules or tumors
nonhealing wounds
odor
otitis
pruritus
scaling and crusting
Etiology of Alopecia in Animals
any disease that can affect hair follicles can cause hair loss.
1) congenital or hereditary
2) acquired.
- inflammatory
- noninflammatory.
the most common cause of alopecia
Inflammatory acquired alopecia
a disease destroys the hair follicle or shaft, interferes with the growth of hair or wool, or causes the animal discomfort (eg, pain, pruritus), leading to self-trauma and loss of hair.
Diseases that can directly cause destruction or damage to the hair shaft or follicle: (5)
Bacterial skin diseases
Dermatophytosis
Demodicosis
Severe inflammatory diseases of the dermis (eg, juvenile cellulitis, deep pyoderma)
Traumatic episodes (eg, burns, radiation)
Diseases that commonly cause pruritus or pain: (4)
infectious skin diseases (eg, bacterial pyoderma and dermatophytosis)
ectoparasites
allergic skin diseases (eg, atopic dermatitis, food allergy, contact, insect hypersensitivity)
less commonly- neoplastic skin diseases
Pruritus in Animals
an unpleasant sensation within the skin that provokes the desire to scratch
It is the most common dermatologic problem in both small and large animals!
most common cause of pruritus is parasites
Infections are common complications of pruritus.
