Dermatology Basics

shape = circle

annular

single

shape = wavy circle

polycyclic

grouped

shape = snake-like

serpiginous

shape = line (roughly)

linear

shape = half moon

arciform

shape = round

iris (central healing)

• circumscribed color change

• normal feel

• primary

• macule (under 1 cm), patch (over 1 cm)

• darker, lighter, or red

macule → patch

• partial or complete absence of hair

• damage to hairs or hair follicles, abnormal hair growth

• normal feel

• primary or secondary

hypotrichosis → alopecia

• excessive hair growth

• normal feel

• primary or secondary

hypertrichosis

• pieces of stratum corneum

• imbalance in keratinization/desquamation homeostasis

• normal feel

scale

• circular scale around abnormal skin

• remains of roof of papule, pustule, hyperkeratosis, vesicle, bulla

• normal-ish feel

• secondary

epidermal collarette

• circumscribed solid elevation

• infiltration of inflammatory cells, edema, or hyperplasia of epidermis

• under 1 cm

• raised

• primary

papule

• circumscribed flat topped elevation

• extension or coalescence of papules

• over 1 cm

• raised

• primary

plaque

• plaque with projecting elevations

• heaped up crusts

• over 1 cm

• raised

• primary

vegetation

• circumscribed elevation of skin with pus inside

• infiltration of neutrophils, usually follicular, can be intraepidermal or subepidermal

• any size

• rounded feel

• primary

pustule

• dermal or SQ accumulation of pus

• larger and deeper than pustule

• raised but pus not visible on skin surface until it drains

abscess

• well circumscribed elevation of epidermis, can be intra-or sub-epidermal

• accumulation of clear fluid, transient

• vesicle (under 1 cm), bulla (over 1 cm)

• raised

• primary

vesicle → bullae

• blackhead: open dilated hair follicle

• hair follicle becomes full of keratin or other secretions

• hair follicle sized

• slightly raised

• primary or secondary

comedone

• whitehead: closed dilated hair follicle

• hair follicle filled with keratin

• primary or secondary

milium

• well circumscribed, annular, flat topped area of dermal edema that pits with pressure

• edema, comes and goes within minutes

• wheal (any), angioedema (many wheals in specific body region)

• raised

• primary

wheal (“hive”)

• epithelial lined cavity with fluid or solid material inside

• infiltration of cornified cellular debris or sebaceous or epitrichial secretions

• any size

• raised

• primary

cyst

• deep well circumscribed skin elevation

• infiltration of inflammatory or neoplastic cells, fibrin, or crystalline material into DERMIS or SQ

• nodule (1-3cm), tumor (over 3 cm)

• raised

• primary

nodule

• epidermal defect that heals without scar

• self-trauma, ruptured papule, pustule, vesicle, bulla

• does NOT breach basement membrane zone

• negative

• secondary

erosion

• epidermal defect that heals WITH scar

• deep pathological process

• DOES breach basement membrane zone

• negative

• secondary

ulcer

• erosion or ulcer that is self-inflicted

• scratching, licking, biting, rubbing

• usually linear

• negative

• secondary

excoriation

• linear split in skin

• thick, dry, inelastic skin subjected to sudden swelling from inflammation or trauma

• epidermal or dermal

• negative

• secondary

fissure

• tract that connects focus of inflammation to skin surface

• inflammation traveling path of least resistance

• negative

• secondary

draining tract

• tract that connects 2 INTERNAL organs or one internal organ to skin surface

• path of least resistance

• secondary

fistula, sinus

• thickening and hardening of skin, exaggerated skin markings, hyperpigmentation

• thick

• secondary

lichenification

• thick, rough, plaque-like area of skin

• pressure, low-grade friction over bony prominence

• thick

• secondary

callus

• accumulation of dried exudate, serum, pus, blood, cells, scales, or medication

• papule, pustule, vesicle, bulla ooze

• rough

• primary or secondary

crust (aka. scab)

• increased thickness of stratum corneum

• rough

• primary or secondary

hyperkeratosis

• region of fibrous tissue that has replaced damaged dermis or SQ tissue

• due to prior trauma, eg. ulcer, burn

• thick

• secondary

scar

• cell death → blue, purple, black, dry, firm tissue

• loss of vascular supply to skin, extremities most common

  • primary or secondary

necrosis

• accumulation of keratin and follicular debris that sticks to hair shaft

• primary or secondary

follicular casting

• whitening of hairs

• lack of pigment in hairs

leukotrichia

• darkening of hairs

• excess pigment in hairs

melanotrichia

• non-follicular bacterial pustular disease

impetigo

puppy impetigo

bullous impetigo

bacterial folliculitis

bacterial furcunculosis

chin and muzzle furunculosis

pedal furunculosis

mucocutaneous pyoderma

feline staphylococcal infection

post-grooming folliculitis and furunculosis

Pseudomonas folliculitis and furunculosis

intertriginous dermatitis

Malassezia dermatitis in dogs

Malassezia dermatitis in cats

Malassezia

dermatophytosis

dermatophytosis in dogs

sylvatic ringworm

immune compromise

onychomycosis

fungal kerion

dermatophytosis in cats

Microsporum canis

Microsporum gypseum

mosquito bite hypersensitivity (type I)

pemphigus vulgaris (type II)

urticaria and angioedema

contact hypersensitivity

face, head and neck pruritus

symmetrical self-induced hair loss (“fur mowing”)

papulocrustous dermatitis (“miliary dermatitis”)

eosinophilic granuloma

eosinophilic plaque

indolent ulcer (“rodent ulcer”)

flea allergy dermatitis in dogs

flea allergy dermatitis in cats

follicular arrest syndrome (aka. alopecia X)

pattern baldness

cyclical flank alopecia

color dilution alopecia

canine hypothyroidism

feline hyperthyroidism

canine hyperadrenocorticism (aka. hypercortisolism, Cushing’s)

feline hyperadrenocorticism

Sertoli cell tumor

left:

right:

bacterial, yeast

ceruminous cystomatotis

SCC or ceruminous gland tumor

primary secretory otitis media (PSOM)

ichthyosis

sebaceous adenitis

feline acne

nasal and digital hyperkeratosis

ear margin dermatosis (seborrhea)

acute moist dermatitis (aka. “hot spot”)

acral lick dermatitis (aka. lick “granuloma”)

tail gland hyperplasia

anal sacculitis

herpesvirus dermatitis

perianal fistulas

juvenile cellulitis