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Chapter 45
Disorders of the Skin
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Skin Infections
• Superficial fungal infections
– Ringworm, athlete’s foot
– Attack the keratinized (dead) cells
– Inflammatory reaction to toxins causes
most signs and symptoms
• Deep fungal infections
– Candidiasis, sporotrichosis
– Attack living tissue
– May attack other organs
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Bacterial Skin Infections
• Impetigo
– May lead to
poststreptococcal
hypersensitivity
reactions
– These can cause
glomerulonephritis
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Viral Skin Infections
• Verrucae (warts)
– Benign neoplasms (papillomas)
• Herpes simplex (cold sores)
• Herpes zoster (shingles)
– Herpes invades dorsal root ganglia
– Caused when chickenpox herpes virus is reactivated
– Travels out nerve to skin and causes a new
inflammation
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Question
Which of the following microbes causes warts?
a. Fungus
b. Virus
c. Bacteria
d. Any of the above may cause warts.
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Answer
b. Virus
Rationale: Warts are caused by viruses; they’re benign
neoplasms (abnormal tissue growths).
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Scenario
Mrs. K is worried about her complexion.
• She says she always had good skin, but
now her face itches and burns on the right
side, and there are red lumps on one side of
her forehead
Question:
• What are the possible causes?
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Acne
• Disorder of sebaceous glands
• Related to:
– Hormonal stimulation of sebaceous glands
– Increased number of sebaceous cells
– Increased sebum production
– Inflammatory response to bacteria in sebum
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Allergic and Hypersensitivity Dermatoses
• Type I allergies
– Atopic eczema
– Urticaria (hives)
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Mast cell
Mechanism of
Type I
Hypersensitivity
Sensitized
mast cell
IgE attaches
to mast cell
Allergen
attaches
to IgE
Mast cell
degranulates
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Type I Allergies
• Type I allergies are mediated by IgE
Discussion:
• What cells must be involved in this process?
– On the first exposure to the allergen?
– On repeated exposure?
– When the allergen binds to IgE?
• What inflammatory mediators are involved? How?
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Question
Which chemical mediator is released by mast cells as part
of the inflammatory response?
a. Histamine
b. Leukotriene
c. Cytokine
d. All of the above
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Answer
a. Histamine
Rationale: Histamine (stored in mast cells) is one of the
first substances to be released during the inflammatory
response. Histamine release results in
bronchoconstriction, mucosal edema, and increased
mucus production.
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Autoimmune Urticaria
• In autoimmune urticaria, the client creates
anti-IgE antibodies
Discussion:
• How would this cause hives?
• How would a deficiency in complement
inhibitor cause hives?
• Why would antihistamines help?
• Why would corticosteroids help?
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Drug-induced Skin Eruptions
• Erythema multiforme
– Occurs after herpes simplex; self-limiting
• Stevens-Johnson syndrome
– Skin detaches from body surface;
<10% of body affected
• Toxic epidermal necrolysis
– >30% of epidermis detaches
– 30%–35% mortality rate
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Papulosquamous Dermatoses
• Psoriasis
• Pityriasis rosea
• Lichen planus
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Activated
T cells
Psoriasis
growth
factors
attract
neutrophils
and
monocytes
keratinocytes
and blood
vessels grow
enter
the
papules
create
papules
create
inflammation
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Burns
• First-degree: outer layers of epidermis
• Second-degree: epidermis and dermis
– Partial-thickness: only part of dermis
– Full-thickness: entire dermis
• Third-degree full-thickness
– Extends into subcutaneous tissue
– May damage muscle, bone, blood vessels
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Scenario
Mr. D was boiling water and the pot tipped over
on him.
• He has painful, bright pink, blistering burns
over most of his left arm and chest
Question:
• How would you categorize this burn?
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Scenario (cont.)
Mr. D’s burns are pink but the rest of his body
looks pale, and he has a rapid heart rate.
• His pulses are weak
• Bowel sounds are absent
• Respiration is rapid
Question:
• What has caused these signs?
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Complications of Burns
• Burn shock
• Respiratory system dysfunction
• Hypermetabolic response
• Renal insufficiency
• Gastric ulceration
• Sepsis
• Constriction of areas under circumferential burns
• Systemic infection
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Scenario
A woman was severely burned and she has been in
the hospital for eight days.
Question:
• Why would she be developing:
– Increased urine production?
– Weight loss?
– Increased temperature?
– GI bleeding?
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Question
Treatment for third-degree burn patients includes all but
which of the following?
a. Fluid replacement
b. Removal of dead tissue/eschar
c. Antibiotics
d. Aloe
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Answer
d. Aloe
Rationale: Patients suffering from third-degree (fullthickness) burns lose fluid through the skin and are
prone to infection. They must receive fluid replacement
and antibiotics to fight or prevent infection. Dead tissue
(eschar) must be removed daily (debridement) in order
to prevent infection. Because third-degree burns destroy
the epidermis, the application of topical aloe would
serve no purpose.
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Pressure Sores
friction
external
pressure
shear
obstructs blood flow
bends blood
vessels
ischemia to skin
damages
dermis/
epidermis
interface
tissue damage
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ultraviolet radiation
melanin oxidized TAN
hits melanocytes
more melanin
produced - delayed
tanning
some UV reaches
lower skin layers
immune
cells
damaged
DNA
damage
inflammatory
mediators
released
sunburn
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UV Damage to DNA
Two thymines next to
one another become
linked: thymine dimers
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Sun Exposure
• Sun exposure increases the risk of skin cancer
• Cumulative sun exposure increases risk of:
– Basal cell carcinoma
– Squamous cell carcinoma
• Severe sun exposure with blistering increases
risk of:
– Malignant melanoma
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Malignant Melanoma
• Cancers arising from melanocytes
• Asymmetry
• Border irregularity
• Color variegation
• Diameter > 0.6 cm
• Evolving change over time
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Types of Melanomas
• 70% are superficial spreading
– Raised edges; grow horizontally and vertically
– Ulcerate and bleed
• 15%–30% are nodular
– Dome-shaped, blue-black
• 4%–10% are lentigo maligna
– Slow growing, flat
• 2%–4% acral lentiginous
– On palms, soles, nail beds, mucous membranes
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Question
Which type of skin cancer is associated with the worst
prognosis?
a. Basal cell
b. Squamous cell
c. Malignant melanoma
d. Ependymal cell
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Answer
c. Malignant melanoma
Rationale: Malignant melanoma begins in the melanocytes
and possesses all of the characteristic features
associated with cancer (asymmetry, irregular border,
many colors, and a diameter > 0.6 cm) as defined by
the American Cancer Society. Basal cell cancer has the
best prognosis, and squamous cell cancer has a good
prognosis as long as it’s detected early.
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Skin Conditions of Infancy
•
•
•
•
•
Birthmarks
Diaper dermatitis
Prickly heat
Cradle cap
Infectious disease rashes
– Roseola (herpes virus)
– Rubeola (measles)
– Rubella (German measles)
– Varicella (chickenpox)
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Skin Disorders of the Elderly
• Actinic (solar) damage
– Keratoses: premalignant lesions
– Lentigines: liver spots
• Vascular lesions
– Angiomas
– Telangiectases
– Venous lakes
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