Dermatology - Skin Lesions

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What are initial eruptions that develop as a direct reflection of underlying disease?

primary lesions

What types of primary lesions exist (8)?

papule, pustule, vesicle, wheal, nodule, macule, tumor, cyst

Pink/red, raised, solid, circumscribed elevation (usu 1mm-few mm but up to 1cm)

papule

small, roundish, epidermal elevation that contains pus (like whitehead pimple)

pustule

small up to 1cm, epidermal elevation with clear fluid, like blister

vesicle

Raised, well-circumscribed, edematous lesion

wheal
hives = urticaria

well-circumscribed, solid lesion that usually occurs deep within the skin

nodule

circumscribed, flat, nonpalpable, small (up to 1cm) spot of skin color change

macule

mass involving the skin or subcutaneous tissue

tumor

epithelium-lined cavity that is filled with solid or fluid material

cyst

What type of lesion may occur due to chewing, scratching, trauma etc, the result of infection or evolve from a ___ lesion?

secondary
may evolve from primary

What types of secondary lesions are there (7)

epidermal collarette, lichenification, callus, fissure, erosion or ulcer, scar, excoriation

What does a papule indicate?

cellular infiltrate - usu represents inflammatory lesion

Does a papule involve hair follicles?

may or may not

What are common causes of papules in dogs & cats?

dogs - bact skin dz (incl pyoderma) & ectoparasites
cats - less common but hypersensitivity/allergic dermatitis, infected feline acne
less common both dogs & cats: pemphigus & contact reactions

What cells do pustules usu contain, and what is less common?

more common NP
less common eos

T/F Pustules always indicate bacterial infection.

False. Can be sterile with pemphigus foliaceus - but less common.

Are pustules sturdy?

no, fragile, rupture easily - may just see ulcer after.

Are vesicles seen commonly?

no, occur infrequently and rupture easily

What are common causes of vesicles?

autoimmune skin diseases, irritant reactions, burns

What is a vesicular lesion >1cm in diameter?

bulla

Describe the skin around a wheal

Usually normal

How long do wheals last?

minutes to hours - short lived

Are wheals a frequent finding?

no - uncommon in dogs, rare in cats

What causes wheals?

insect bites, or non-insect related allergic reactions

What are causes of nodules?

Inflammatory or neoplastic cellular infiltration in the dermis or subcutis

What is a neoplastic nodule called?

tumor

A macule larger than 1cm diameter is a ?

patch

T/F: all macules are hyperpigmented, and erythematous

F - can be hyper or hypo, erythematous or hemorrhagic

Are macules commonly seen?

Yes, in dogs as a postinflammatory, hyperpigmented change

Are tumors neoplastic?

yes

Describe the texture of cysts?

soft/floculant or firm. Follicular are often firm

A circular ring of scale/peeling keratin

epidermal collarette

Thickening of the skin, characterized by an exaggeration of the normal skin surface markings

Lichenification

A thickened, rough, alopecic, hyperkeratotic plaque like lesion

callus

A linear cleavage into or through the epidermis - crack in skin

fissure

epidermal defect that does not penetrate the BMZ and heals without scaring

erosion

epidermal defect that is deeper than an erosion, exposes dermis and often heals with scarring

ulcer

fibrous tissue replacement of normal epidermis, dermis or subcutis

scar

Erosions or ulcers resulting from self-trauma (excessive scratching, biting, rubbing)

excoriation

What is often a remnant of a papule or pustule?

epidermal collarette

What results from friction and is often indicative of chronicity?

lichenification

What is commonly seen over bony areas and is caused by pressure and friction?

callus

Where are fissures found and are they found frequently?

footpads, ear margins, nasal, oral or anal mucocutaneous junctions
Uncommon but with various disease etiologies, including trauma.

Self-trauma, and conditions affecting the epidermis may lead to a ?

erosion

infection, neoplasia, vasculitis, certain autoimmune skin diseases and burns may lead to ?

ulcers

Burns or deep infections may cause

scars

Often created in response to pruritis, less commoly pain

excoriation

Lesions that can be either primary or secondary (7)

alopecia, scale, crust, follicular cast, comedo, pigmentary abnormalities, erythema

Abnormal hair loss =

alopecia

partial abnormal hair loss

hypotrichosis or partial alopecia

Accumulation of loose, cornified skin cells (flaky skin, dandruff)

scale

dried exudate, serum, cells, blood, scales (a scab)

crust

a cylindrical accumulation of keratin that is adhered to (surrounds) a hair shaft

follicular cast

a plugged follicle that contains keratin (and may contain sebum and cornified skin cells)

comedo

Describe the different pigmentary abnormalities (5)

hyper, hypo pigmentation, malanotrichia (excess hair pigment), leukotrichia (lack of hair pigment) leukoderma (nonpigmented skin)

excessive hair pigment =

melanotrichia

lack of hair pigment vs nonpigmented skin

leukotrichia vs leukoderma

redness of the skin often due to congestion of skin capillaries

erythema

Endocrine diseases and follicular dysplasias may cause ___ alopecia.

primary

Skin infections, inflammation of the skin and self-induced trauma may cause ___ alopecia.

secondary

Primary seborrhea, ichthyosis, follicular dysplasia and sebaceous adenitis may cause ____ scale.

primary

Common and non-specific, occurs with many infections and inflammatory conditions ____ scale.

secondary

Zinc-responsive dermatosis and in some cases primary seborrhea occur with ___ crusting.

Primary

Pyoderma and pruritic dermatoses and many dermatoses occur with ___ crusting.

secondary

Sebaceous adenitis and primary seborrhea associate with ___ follicular casts.

primary

Dermatophytosis and demodicosis are associated with ___ follicular casts.

secondary

Hypopgimentation from vitilago is an example of ___ pigment abnormality.

primary

A common postinflammatory change in dogs is ____ hyperpigmentation.

secondary

A common result from a variety of different dermatologic conditions.

erythema

Configuration of skin lesions
Number

single or multiple

Config of skin lesions: shape

annular (ring), linear or serpiginous or other

Shape seen with bacterial folliculitis, dermatophytosis, demodicosis

annular pattern

Shape seen with excoriations, external forces, lesions with vessel involvement, some congenital conditions

Linear

Having wavy, indented or undulating margins =

serpiginous

Which diseases have diffuse distributions?

some endocrine, allergic and keratinization defects

T/F we often see the original lesion

False - lesions change as they progress - often see footprints of the lesion

What are the 10 parts of history to dx?

Signalment
Chief complaint
Onset of derm prob
Disease progression
Past response to tx
seasonality
pruritic?
enviornmental & dietary history
other animals/people with problem
any non-derm dz present?

What part of signalment can be important for some dermatoses?

coat color

Physical exam - 6 components?

1) good overall PE
2) skin - what lesions present
3) configuration of lesions
4) distribution of lesions
5) pruritic?
6) painful? - rare

T/F painful skin conditions are common

False - rare

Lab procedure good for detecting ectoparasites such as mites?

skin scrapings

Lab procedure good for finding ectoparasites including Cheyletiella and fleas

flea combing

Lab proceedure to find ectoparaisites, esp cheyletiella

acetate tape impressions

What can be used to assess self-induced alopecia, dermatophytes, ectoparasites, color distribution alopecia, hair dysplasias, hair shaft abnormalities, hair growth stage (anagen vs telogen)?

hair examination (trichography)

What is used to look at cell types as indicators of infection, autoimmune dz, neoplasia, allergy, ectoparasite etc - and sometimes see infectious organisms?

cytology

What is the most reliable way to detect dermatophytes?

culture

What is useful for deeper fungal infections and some, esp deep bacterial skin infections?

culture

What is used to assess dermatophytosis but not great?

Wood's lamp - only 50% flouresce

What is necessary to definitively diagnose certain derm conditions?

Biopsy and dermatohistopathology

When a condition does respond to appropriate therapy what do you do?

biopsy & dermatohistopathology

For unusual or serious dermatoses or suspected autoimmune conditions - test?

biopsy & dermatohistopathology

For conditions that aren't easily diagnosed w/o biopsy - test?

biopsy & dermatohistopathology

For persistent ulcerated dermatoses - test?

biopsy & dermatohistopathology

For vesicular conditions - test?

biopsy & dermatohistopathology - rare

For suspected dermatoses for which treatment may be dangerous - test?

biopsy & dermatohistopathology

For possible neoplastic lesions - test?

biopsy & dermatohistopathology

What types of allergy testing are available?

intradermal or skin
in vitro testing - serologic
diet trial for food allergy
patch testing - rare

When are bloodwork and urinalysis helpful?

Cases of endocrinopathy and certain autoimmune conditions. For most derm cases - little diagnostic value

What other tests might be used?

Antinuclear antibody (ANA) to evaluate thyroid hormone, screening and differentiating tests for hyperadrenocorticism

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