Download INTRO TO DERMATOLOGY [Dermatology

INTRO TO DERMATOLOGY
[Dermatology - Study of the skin, hair, glands, nails
Dermatologist - specialist of the skin
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-Epidermis - outermost, no blood vessels or blood supply
-New layer produced every 30 days
-Waterproof, functions as barrier to microorganisms
-Dermis - vascular layer/sensation. Strength and elasticity to the skin.
-Does not regenerate
-Scar: fibrous tissue that replaces normal tissue after dermis has been destructed
-No sweat glands, no hair follicles
-Located below epidermis
-Hypodermis - subcutaneous layer - protects bone, tendon, muscles
-Helps attach the skin to muscles below
-Insulation, protection, energy source
-Accessory structures: hair, nails, glands
EPIDERMIS
-Stratum corneum - outermost layer
-15-30 layers of flattened dead keratinized cells
-Tightly connected by desmosomes
-Sheds 40 lbs over a human lifetime
-Stratum lucidum - only found in palms and soles
-Thin layer of flat cells, present in thick skin
-Helps reduce friction  protection
-Stratum granulosum - few layers of flattened cells containing keratohyalin
-Produce keratin, release lipids (water resistance)
-Stratum spinosum - formed as basal layer moves outward towards surface
-2-4 cell layers thick, has desmosomes (have spiny projections)
-Langerhan cells -- important for immunity
-Keratinocytes -- produce keratin
-Stratum basale - deepest layer of the epidermis
-Single layer of keratinocytes and melanocytes
-Produce melanin
-Covers basement membrane (basal lamina) - separates epidermis from dermis
-Undergo rapid cell division to produce more cells
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Melanocytes - produce melanin, not many in soles or palms of hands
-Albinos lack tyrosinase - enzyme required to make melanin
-Cancer of melanocyte = melanoma, fast metastasizing
Keratinocytes - produce keratin
-Secrets cytokines and inflammatory mediators
-Protection and waterproofing
Merkel’s cells - touch receptors found in fingers, toes, mouth
-Free nerve endings attached to epidermal cells
Langerhans cells - derived from bone marrow, involved in hypersensitivity, antigen processing,
etc
Parakeratosis - retention of nuclei in stratum corneum (usually dead)
-Hypertrophy of the corneum (hyperkeratosis)
-Flaky, scaly skin
Spongiosis - intercellular edema of the epidermis - leads to inflammation
-Physically pulls epidermis away from each other - intraepidermal vesicles (contact
dermatitis, eczema)
Basal lamina (Basement membrane)
-Separates dermis from epidermis
-Allows epidermis to adhere to dermis
-Selectively filters molecules moving bt two layers, prevents malignant cells from moving any
deeper
-Blister formation from immunoglobulin and complement deposition
DERMIS
-Thickest skin layer/connective tissue layer
-Separates epidermis from subcutaneous fat layer
-Strong, flexible
-Composed of collagen, blood vessels, nerves, ,hair follicles, sweat glands
-Provides nutrition
-Thermoregulation, protection
SUBCUTANEOUS TISSUE
-Fat, blood vessels
-Eccrine glands and deep hair follicles extend to this layer
-Important insulator, shock absorber, stores energy
HAIR
-Associated with sebaceous gland  pilosebaceous unit
-No new hair follicles after birth, some need hormonal stimulation
-Made of keratin
-Growth is cyclic
-Anagen - 90% of hair follicles undergo growth
-Catagen- hair falls out, new hair begins to grow
-Telogen - resting phase (10% of time)
Hair loss due to-Stress, poor nutrition, genetics, hormones, pregnancy, medications
NAILS
-Hardened keratinized plates - dead cells
-Grow under the lunula (white portion on bottom of nailbed)
-Protection, dexterity
-Grow continuously bc they are continuously produced (keratin)
GLANDS
Sebaceous - Entire skin surface except palms, soles, sides of feet, secrete sebum
-Sebum: lipids, cholesterol, wax
-Mildly bactericidal, lubricates
-Influenced by hormones, adolescence
Sweat - found in hands, soles, axillae
-eccrine - originate in dermis and open on skin surface
-apocrine - large deep in dermal layer, secrete oily substance
-mixed with bacteria = body odor
-odor can also be caused by fat and protein and sweat decompose
SKIN LESIONS EQUAL TO PLANE OF SKIN
Macule - circumscribed, round, up to 1 cm in diameter, flat, distinguished from surrounding skin
by color - freckles
Patch - large macule greater than 1 cm in diameter, flat
Telangiectasia - spider veins - dilated superficial blood vessels (found in scleroderma, cirrhosis)
Petechiae - small, non-blanching erythematous macules <2mm in diameter, pinhead size, due to
rupture of small blood vessels which lead to minor hemorrhage (don’t go away when you press
on it) - sign of thrombocytopenia - low platelet count
Purpura - >2mm, large petechiae  discoloration of skin, mucous membrane due to
hemorrhage, non-blanching, reddish discoloration
-Ecchymosis - blueish discoloration, deeper bleeding in skin
Sclerosis - hardening, immobility of affected skin (induration)
Lichenification - focal area of thickened skin with accentuation of skin markings (skin lines) due
to repeated rubbing or scratching in a susceptible patient (ie patients with eczema)
Acanthosis - thickening of epidermis on neck, under the arms, in groin area, due to elevated
levels of insulin (activate receptors in skin), proliferation of keratinocytes (parakeratosis)
ABOVE PLANE
Actinic Keratosis - rough, raised spot on skin, found on skin chronically exposed to the sun (precancerous) - can appear light, dark, pink or red in color
Hyperkeratosis - hypertrophy of stratum corneum - excessive keratin being produced
Callus - thickening and enlargement of stratum corneum (hyperkeratosis leads to callus)
Corn - small callused area caused by local pressure, irritating tissue over a bony prominence
Papule - well circumscribed, elevated solid lesion up to about 1cm in diameter, usually dome
shaped
Nodule - palpable solid region that can involve the epidermis, dermis, subQ layer; can be due to
neoplasm, usually bt .5 - 2 cm in diameter, deeper in skin than papule
Wheal - transient, pink/red raised area with central pallor; shape and size of wheals vary (hives,
mosquito bites)
Plaque - elevated, flat-topped area, usually >1cm in diameter, rarely >5mm in height
Vesicle - raised, contain serous fluid, usually 1 cm or less in diameter
Bulla - large vesicle, >1cm
Pustule - discrete pus-filled raised area (acne, folliculitis) filled with leukocytes or dead cellular
material
Cyst - elevated, encapsulated mass, can be semi-solid or fluid filled, epithelial lined, contains fluid
or semi-solid material inside
Tumor - Well demarcated (can tell borders around it), usually >2cm in diameter (increasing size:
papule --> nodule --> tumor)
Verruca - epidermal growth due to a virus - wart
Scale/crust - flakes of the stratum corneum; can be large membrane or tiny (like dust), can
adhere to skin (scab) or can be loose (dandruff in hair); white area = scaling; crust = dried
serum, blood or pus on surface of skin
Desquamation - peeling of the skin
Exudate - fluid that has exuded from a tissue or capillary due to inflammation or injury; can be
serum, blood or pus
Comedone - enlarged hair follicles plugged with oil, bacteria (acne) - can be either whiteheads or
blackheads
BELOW PLANE OF SKIN
Erosion - loss of the superficial layer of the upper epidermis by wearing away from friction or
pressure
Ulcer - indentation in skin - crater-like; circumscribed area of skin loss extending through the
epidermis through the dermis, subQ layer, may extend to muscle and bone (decubitus ulcers)
Fissure - small crack or break in skin which exposes the dermis and appears erythemic (paper
cut)
Excoriation - traumatic self-induced lesion due to scratching; erythematous; makes pt prone to
infection
Eschar - thick, coagulated crust or slough which develops following a burn
Disorders of Pigmentation and Melanocytes
Vitiligo - Melanocytes are destroyed - leads to white patches on skin - possibly autoimmune
disorder
Albinism - have melanocytes but lack tyrosinase enzyme, melanin cannot be produced - no
protection from sun’s rays
Melasma - mass-like zone of facial melanosis (hyperpigmentation) - known as chloasma in
pregnancy
Lentigo - melanocyte proliferation - small, circumscribed, pigmented macule surrounded by
normal skin - can be due to hyperkeratosis, Addison’s disease, hemochromatosis; may be
bleached by hydroquinone
Skin Lesions Based on Color
Erythema - redness due to capillary dilation, inflammation, cellulitis or sunburn
-Blanches with pressure - intact capillaries
Cyanosis - blueish discoloration usually due to hypoxia
Jaundice - yellow staining of the skin due to bile pigments and increased levels in the plasma
Approach to pt
Normal vs. abnormal
Appropriate differential diagnosis
Pros of dermatology - visual, no special instrumentation, easy biopsy
Cons of dermatology - easily misled by variety of stimuli and overall look of disease -- subtle
Hx
Acute vs. chronic
Onset - when/how it started
Subjective symptoms - does it hurt/itch/burn/etc
Location - where it started
Distribution - where is it? - generalized, specific
Spread, change in lesions - chicken pox, herpes zoster
What makes it worse/better
Has there been contact with anyone with a similar rash?
Did you get a new pet?
Recent travel?
Physical Exam
FOUR points:
Type of Lesion
Shape
Arrangement
Distribution
Palpate lesions - are they consistent? Tender? Temperature change? Mobility? Margins?
Systemic exam: lymphadenopathy (bacterial infection, elephantitis), organomegaly, jaundice,
arthralgia, neurological changes
Rash - temporary eruption of the skin seen in childhood disease, in heat, drug-induced, diaper
rash, etc
Lesion - break in tissue integrity, continuity - pathological or traumatic change in tissue
Shape of the lesion
-Round
-Oval
-Polygonal
-Annular - circular, ring shaped
-Serpenginious - snakelike
-Umbilicated - indentation in the middle
Arrangement of lesions
-Grouped - herpetiform (like herpes), arciform (in an arc), annular (ring shaped), reticulated
(web)
-Disseminated - widely scattered, discretely with borders; can be either discrete or diffuse
(cannot tell where borders end)
-Demarcated - (may or may not be discrete) have clear boundaries - each individual lesion is
pointed out
-Diffuse - no clear boundaries - opposite of demarcated
Extent: isolated, localized, regional, generalized, universal
Pattern: symmetrical, exposed areas (substance, sun), pressure related (heels), random
-Any characteristic patterns such as seen in acne, chicken pox
Darier sign - rubbing on lesion leads to wheal or flare
Auspitz sign - pinpoint bleeding after scales are removed - common in psoriasis
Nikolsky sign - slight rubbing causes separation of the skin layers (desquamation)
Diascopy - putting a glass slide against the skin - blanching = capillaries are intact (ie suburn);
non-blanching = capillaries broken
Koebner phenomenon - minor scratching leads to lesions
Diagnostic Techniques
Wood Light Exam: Use ultraviolet light
-Some organisms turn colors under light
-Green fluorescence in tinea capitis
-Skin: erythrasma (chronic bilateral infection caused by cornybacteria): bacteria give
coral red fluorescence
-Hypomelanosis: decrease in intensity
Acetowhitening: acetic acid allows a transient whitening of penile or vulvar (genital) warts
Patch test: for allergies - hypersensitivity test where pt is pricked with diff allergens to see where
they produce a response
KOH preparation: dissolves keratin and cellular material, does not affect fungi (tinea capitis)
For bacteria: gram stain
For virus: Tzanck smear
For spirochetes: dark field examination - spirochetes appear bright spiral objects against black
background
Cultures: used for bacterial, viral, parasitic, mycologic
Biopsy: used for diagnosis