CH. 17 DISEASES OF
THE SKIN
SWCTA
Dr. Michael J. Georges
I. FUNCTIONS OF THE SKIN
 The skin or the integument is a vital organ
 A “protective wrap”
 Regulates body temperature
 Senses pain
 Keeps harmful substances & microorganisms
from entering body
 Provides a shield from harmful effects of the
sun
 Largest organ of the human body
I. FUNCTIONS OF THE SKIN
 Indicates malfunction within the body through
color changes
 Cyanosis (blue) is lack of O2-cardiovascular
problem
 Jaundice (yellow) – indicates liver disease
from accumulation of bilirubin in the blood
 Abnormal redness – due to polycythemia,
carbon monoxide poisoning, & fever
 Pallor (whitening) may indicate anemia
II. STRUCTURE OF THE SKIN
Each layer of skin performs specific tasks
 OUTERMOST layer is the EPIDERMIS
 Consists of stratified or squamous epithelium
 Top layer of epidermis contains KERATIN – a
tough, fibrous protein that protects skin from
harmful substances
 Bottom layer of epidermis contains MELANIN
– dark pigment in skin that protects body from
harmful rays of the sun
II. STRUCTURE OF THE SKIN
 DERMIS – “True Skin”
 SUBCUTANEOUS –lies
lies below the epidermis
 Composed of
connective tissue
 Supports blood & lymph
vessels, elastic fibers,
nerves, hair follicle,
sweat glands &
sebaceous (oil) glands
under the dermis
 Connects the skin to
underlying structures
(i.e. muscle, fat)
 Contains adipose (fat
cells) tissue – helps
insulate body from cold
& heat
 Fig. 18-1 pg. 397
Structure of the Skin
III. CLASSIFICATIONS OF SKIN
DISEASES
 Skin diseases are identified and classified
according to characteristic lesions (size,
shape, color & location) and other S & Sx’s
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Fig. 18-2 Skin signs pg. 398
 PRURITIS – itching
 EDEMA – swelling
 ERYTHEMA – redness
 Inflammation –usually accompany lesions
and are helpful in making a diagnosis (DX)
III. CLASSIFICATIONS OF SKIN
DISEASES
 VESICLES – small blister-like eruptions or
larger fluid-filled lesions called bullae.
 PUSTULES – lesions that contain pus
 MACULAR – flat lesions
 PAPULAR – raised lesions
 ERYTHEMATOUS – reddened area due to
inflammation &/or injury
 Nodules & tumors – hard to the touch
 Pruritis – itching, which accompanies many
skin diseases, especially allergic & parasitic
IV. INFECTIOUS SKIN DISEASES
BACTERIAL
 IMPETIGO – is acute, contagious &
common in children
 Caused by streptococcal & staphylococcal
organisms in the nose & passed to the skin
 Erythema, reddened area develops and
oozing vesicles and pustules form
 Area ruptures & yellow crust covers lesion
 Face & Hands most frequently affected
 Fever & enlarged lymph nodes may present
 Wash with soap & H20, dry, keep open to air
IV. INFECTIOUS SKIN DISEASE
BACTERIAL
 ERYSIPELAS – inflammatory skin
infection caused by streptococci
 Commonly appears on face, arm or leg
 Infection begins where skin is broken
 Shiny, swollen, red rash initially develops,
often with small blisters
 Red rash is hot & tender to touch
 Fever & chills present when infection severe
 Treatment with antibiotics (ABX) when severe
IV. INFECTIOUS SKIN DISEASE
BACTERIAL
 CELLULITIS - spreading infection of the
skin most often caused by streptococcus
 Most common on the legs and begins with
skin damage
 Affected area is swollen, red, & tender
 Sx’s may include fever & chills
 Treatment (TX)– prompt TX prevents the
spread of infection to the blood & vital organs
IV. INFECTIOUS SKIN DISEASES
BACTERIAL
 FOLLICULITIS – inflammation of hair follicles by staphylococci
Small number of pustules develop in follicle
 Commonly occurs in young men and affects thighs, buttocks, beard
& scalp (Fig.18-4 p.400)
 TX-severe cases require oral ABX
 CARBUNCLES- clusters of boils.
 Arise in cluster of hair follicles
 Develop & heal more slowly than furuncles
 Mostly appears in men and commonly found on back of neck
 FURUNCLES – “boils” are large, tender, swollen raised lesions
caused by staph (Fig. 18-5 p. 401)
 Appears in hair follicles on face, neck, breast, or buttocks
 The core of furuncle is necrotic & liquefies to form pus
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 TX-moist heat, antiseptic skin cleansing, oral ABX, I & D
VIRAL SKIN INFECTIONS
Most common viruses cause cold sores or fever
blisters & warts
 HERPES SIMPLEX – causes cold sores &
fever blisters (Fig. 18-6 p. 401)
 VERUCCA VULGARIS – causes WARTS
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Keratinocytes proliferate making the surface rough
Most common in children & young adults
Affects mostly the hands (Fig. 18-7 p.402)
Multiple & CONTAGIOUS – spread by scratching
Reoccurs if virus remains in body, not serious
May disappear spontaneously, not painful
Should only be removed by an M.D.
VIRAL SKIN INFECTIONS
WARTS
 PLANTAR WARTS – found on the SOLES
OF THE FOOT
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GROWS INWARD, unlike other warts on the
body which grow outward (elevated)
Painful, due to pressure on the soles of the
foot when walking or standing
Difficult to remove permanently
 GENITAL (VENEREAL) WARTS – very
serious & difficult to remove (CH. 15)
VIRAL SKIN INFECTIONS
FUNGAL
 DERMATOPHYTES (FUNGI) – live on the
dead, top layer of the skin
 Symptoms may or may not appear
 Serious infections – itching, swelling, blisters
& severe scales
 Minor infections – mild irritation & swelling
VIRAL SKIN INFECTION
FUNGAL
 RINGWORM (TINEA) –
caused by many
different fungi.
Classified by its location
on the body (Table 18-1)
 Found on warm, moist areas
of the body and hairy skin on
head, groin, arms, & legs
 SX’s – mild scales, cracking
skin, to painful raw rashes
 TX- keep area clean & dry,
apply antifungal meds.
 TINEA CORPORIS –
Body ringworm, smooth
areas, arms, legs, body
 TINEA PEDIS –
”ATHLETES FOOT”
soles, btwn toes, toenail
 TINEA CRURIS –
“JOCK ITCH” groin &
upper thighs
 TINEA CAPITIS –
“SCALP” ringworm.
HIGHLY CONTAGIOUS
PARASITIC INFESTATIONS
3 Categories
 PEDICULOSIS – Louse (lice) infestations
 HEAD LICE – common among children
 Spread from head to head (direct)
 Indirect – combs, scarves, hats, bed linen,etc
 Itching – caused by saliva of lice penetrating skin &
engorging on human blood
 Scratching – can open up skin to other invading
organisms
 Adult head lice – hard to see, lay white eggs “NITS”
along hair shaft
 TX – Medicated shampoo followed by fine tooth comb
to remove nits
PARASITIC INFESTATIONS
 PUBIC LICE – infest pubic hair and generally
spread by sexual contact.
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Lice does not spread other STD’s
TX – RX Cream
 BODY LICE – most common among
underprivileged, transient people.
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Lice CAN SPREAD DISEASE – such as
typhus epidemics among soldiers during war
Prevention – good grooming & hygiene
PARASITIC INFESTATIONS
 SCABIES “THE ITCH” – caused by a parasitic
MITE
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HIGHLY CONTAGIOUS
Female mite – burrows into skin folds of groin, under
breasts, between fingers & toes. Lays eggs in tunnels
of folds, eggs hatch, cycle begins again
Spread via close contact & linked to other VD’s
Blisters & pustules appear
Itching – caused by hypersensitivity to mite & opens up
skin to other bacterial infections
Epidemics common in camps & barracks (poor living)
TX & Recovery – Hot baths & scrubbing & meds.
Underwear & bedding changed & washed frequently.
V. HYPERSENSITIVITY OR
IMMUNE DISEASES OF THE SKIN
 HYPERSENSITIVITY – ALLERGIC reactions
of the skin. Emotional stress may trigger or
exacerbate an allergy-caused skin disease.
 INSECT BITES – Bites & stings can produce
local inflammatory reactions.
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Acute reactions – hives
Chronic reactions – papules (solid elevations)
Bullous - blisters
HYPERSENSITIVITY OR IMMUNE
DISEASES OF THE SKIN
 URTICARIA (HIVES) – VASCULAR
REACTION OF THE SKIN TO AN
ALLERGEN
 WHEALS – lesions round elevations with red
edges & pale centers
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Extremely itchy
Histamine released – cause blood vessels to
dilate, followed by edema & intense itching
Common causes – food, allergens & stress
TX- steroids, antihistamines, topical creams
HYPERSENSITIVITY OR IMMUNE
DISEASES OF THE SKIN
 ECZEMA – AKA CONTACT DERMATITIS is a non
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contagious inflammatory skin disorder.
Cause – sensitization that develops from skin contact
with various agents, plants, chemical, & metals.
Poison ivy and poison oak, dyes used for hair &
clothes, metals, particularly nickel used in jewelry.
S & Sx’s – Vesicles & bullae appear with itching.
Scaly crusts form on ruptured lesions.
Scratching – causes the lesions to burst & ooze
which spreads the eczema.
TX – Corticosteroids to reduce inflammation
Fig. 18-10 p.406
HYPERSENSITIVITY OR IMMUNE
DISEASES OF THE SKIN
 POISON IVY – causes
extreme itching with blisters
and hive-like swelling typical
of a contact dermatitis
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Develops in few hours
or few days
 Severity – depends on
amount of plant resin on skin
& sensitivity of ind.
 TX- Topical cortisone-type
cream, gel or spray.
 Table 18-2 Common rashes
caused by Drugs p. 407.
 DRUG ERUPTIONS –
Adverse drug reactions
manifest more often on the
skin than any other organ
system.
 Topical drugs – mild pimples
over sm. Area to peeling of
the skin
 Serious reactions may lead
to anaphylaxis shock or
death.
 Most common offending
drugs are penicillin, sulfa,
morphine, codeine, etc.
VI. BENIGN TUMORS
 NEVUS (MOLE) – small, dark skin growth
that develops from pigment-producing cells or
melanocytes.
 Appear flat or raised & vary in size
 Most people have about 10 moles
 Usually harmless, but can become malignant
 Sudden changes in moles such as
enlargement, irregular border, darkening,
inflammation & bleeding are warning signs of
malignancy (Fig. 18-15 & 18-16 p. 409)
VII. SKIN CANCER
 BASAL CELL CARCINOMA – most common skin
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cancer. Slow growing, generally non-metastasizing
(spreading) tumor.
Develops on face of light skinned people exposed to
sun
Lesions begin as a pearly nodule with rolled edges
that may bleed and form a crust
Ulceration occurs and size increases if neglected
TX- surgical removal, cauterize, or radiation.
Fig. 18-17 to 18-19 p. 410.
VII. SKIN CANCER
 SQUAMOUS CELL CARCINOMA – more serious
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than basal cell carcinoma because it grows more
rapidly, infiltrates underlying tissue, and metastasizes
in lymph system.
Malignancy of the keratinocytes in the epidermis of
people who are excessively exposed to sun.
Lesion is crusted nodule that ulcerates & bleeds.
May develop in any squamous epithelium of the body
including the skin or mucous membranes lining a
natural body opening (mouth, nose, ear, etc.)
TX – complete surgical removal or radiation therapy.
VII. SKIN CANCER
 KAPOSI’S SARCOMA – Purplish neoplasm
of the lower extremities.
 Lesions – red to purple lesions varying from
macules (flat) to nodules (hard nodes)
 This skin cancer is epidemic in AIDS patients
 Cause of 11% of AIDS-related deaths
VII. SKIN CANCER
 MALIGNANT MELANOMA – the MOST SERIOUS
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skin cancer. Arises from the melanocytes of the
epidermis.
HIGHLY MALIGNANT and metastasis is early
Sometimes develops as a mole that changes in size,
color & becomes itchy & sore.
TX-surgical removal with the surrounding lymph
nodes to reduce metastasis
Prognosis-depends on depth of infiltration, previous
metastasis, & how completely the tumor is removed.
Fig. 18-21 Malignant melanoma spread to brain.
VIII. SEBACEOUS GLAND
DISORDERS
 Hyperactivity of the sebaceous glands causes acne
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and chronic dandruff. Raised, horny lesions result
from an excessive production of keratinocytes.
ACNE (VULGARIS) – blackheads, pimples and
pustules.
Affects many adolescents, about 80% between the
ages of 12 – 15.
Mild form – non-inflammatory acne with few white &
black heads.
Inflammatory acne – severe breakout of pus-filled
pimples & cysts that cause deep pitting & scarring
SEBACEOUS GLAND DISORDERS
ACNE
 Result of hormonal changes
that occur at puberty
 Increased level of estrogen &
testosterone stimulates not only
growth at this time but also
glandular activity
 SEBACEOUS GLANDS
increase secretion of SEBUM,
the oily fluid that is released
through the hair follicles.
 If duct becomes clogged by dirt
or make-up, the sebaceous
secretion accumulates, causing
a little bump or whitehead
 Sebaceous accumulation at the
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surface becomes oxidized and
turns black, causing a
blackhead
Blackheads should not be
squeezed or picked because
the broken skin offers entry of
bacteria that’s always present
on the skin
Once pyogenic (pus producing)
bacteria enters the skin, pus
forms and a pimple or pustule
“whitehead” results.
Squeezing the pimple spreads
the infection
TX- daily frequent & thorough
washing to remove excess oil &
bacteria. Dermatologist may
prescribe topical or oral ABX.
SEBACEOUS GLAND DISORDERS
SEBORRHEIC DERMATITIS
 KNOWN AS “CHRONIC DANDRUFF”
 CAUSE-same as acne, an excessive
secretion of sebum from the sebaceous gland
 SX’s- Oily scalp, with scales that form from
excess sebum
 Can spread to face, ears & eyebrows
 TX – frequent shampooing with medicated
shampoo and thorough brushing of hair
loosens dandruff scales & washes out easily
SEBACEOUS GLAND DISORDERS
 SEBACEOUS CYSTS-
 ACNE ROSACEA-
formed when gland duct
becomes blocked, sebum
accumulates under the
skin surface, forming a
lump.
 These cysts are NOT
considered serious, but
they can rupture, allowing
bacteria to enter.
 TX-incision & drainage or
surgical removal
condition that appears
during or after middle age
in persons with fair skin.
 Usually cheeks, chin &
nose develop tiny pimples
and broken blood vessels
that eventually thicken and
gives the nose a bulbous
appearance.
 Cause: NOT KNOWN
 TX – Responds well to
topical ABX
IX. METABOLIC SKIN
DISORDER
 PSORIASIS – a superficial recurring idiopathic
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(unknown cause) skin disorder characterized by an
abnormal rate of epidermal cell production and
turnover.
Rapid replacement of epidermal cells results in
formation of red, round, raised lesions with silvery
scales.
Occurs on elbows, knees, & scalp (mistaken for
severe dandruff) which flairs up and has periods of
remission & exacerbation
Cause – NOT KNOWN
TX-application of emollient cream, topical & oral
steroids, coal tar cream & UV light. Severe psoriasis
can be treated with anticancer meds.
X.
PIGMENT DISORDERS
The main skin pigment, MELANIN, is interspersed among other cells
in the epidermis. Skin color varies from light to dark depending on the
number of melanocytes. Melanin production normally increases with
exposure to the sunlight causing tanning.
 ALBINISM –A rare
INHERITED disorder in
which NO MELANIN is
formed
 An Albino person has white
hair, pale skin, & pink eyes
 Because melanin protects
the skin, Albinos are prone
to sunburn and skin cancer
 VITILIGO – A loss of
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melanin resulting in white
patches of skin.
White patches are well
defined (demarcated) and
may cover large parts of the
body
Hypo-pigmentation is most
striking in dark-skinned
people
The affected skin is prone to
sunburn
NO CURE
TX - SUNSCREEN
XI. DIAGNOSTIC TESTS FOR
SKIN DISEASES
 Skin conditions are normally identified by its
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characteristics such as size, shape, color, location &
presence or absence of systemic S&SX’s
Culturing the purulent lesion usually identifies the
bacterial, fungal, and viral infections.
Culture grows & specimen is identified under a
microscope
Biopsies (tissue sample) are usual for neoplastic
(abnormal new growth) lesions, chronic eruptions,
and nodular lesions
Excised tissue is about 1/8 inch in diameter and is
examined under a microscope.
XII. SUMMARY
 The skin protects the body from various elements in the
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environment, it can become diseased in many ways.
Skin infections may be caused by bacterial, viral, fungal &
parasitic infestations.
Skin diseases frequently manifest allergies due to
hypersensitivity or immune conditions.
Abnormal growth or neoplasms may be benign or malignant and
range from the common mole to malignant melanoma (skin
cancer).
Skin lesions take many forms, each of which is significant
in diagnosing the disease. The location of the lesion,
whether it tends to recur, and whether it itches, are also
factors in the diagnosis.
To rule out systemic conditions, blood tests and other laboratory
tests may be performed.