Fifth Stage
Dermatology
Dr. Hadaf – Lecture 6
1
Objectives
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By the end of this lecture, the student should be able to:
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Classify the main physical factors in the environment
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Describe the skin changes induced by these factors
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Recognize the main preventive measures for these conditions & their best
treatment modalities.
Physical factors in the environment
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Heat
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Cold
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Sun
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Physical pressure
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Radiation
Heat
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Burn
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Miliaria
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Erythema ab igne
Burn
o
Thermal
o
Electrical
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1
st
degree: only erythema + sometimes desquamation+constitutional symptoms if
a large area is involved
•
2
nd
degree:
A- superficial B- deep
superficial deep
causing vesicles & bullae causing pallor
heal without scarring delayed healing with scarring
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3
rd
degree: full thickness loss of tissue with scarring
2
Miliaria
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Occlusion of eccrine sweat gland leads to retention of sweat with failure of
delivery of sweat to the skin surface.
•
Eventually backed-up pressure causes rupture of sweat gland or duct at different
levels.
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Escape of sweat into adjacent tissue produces miliaria.
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Common in hot, humid climates.
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Different forms of miliaria occur depending on the level of injury to the sweat
gland.
1- Miliaria crystallina
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-Small, clear, superficial vesicles without
inflammation.
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-Appears in bedridden pts and bundled children.
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-Lesions are asymptomatic and rupture at the
slightest trauma.
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-Self-limited; no treatment is required.
2-Miliarai rubra
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Discrete, extremely pruritic, erythematous
papulovesicles with sensation of prickling, burning, or
tingling.
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-Site of injury is prickle cell layer.
3-Miliaria profundal
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Occlusion is in the papillary dermis
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Only seen in tropics
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Rare in our country
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Deep seated flesh colored papules
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asymptomatic
Treatment
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Mild cases respond to cooling of skin
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Place patient in a cool environment
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Use dusting powder as talcum
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Cooling baths of menthol & corn starch
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Emollients & steroid ointment to dissolve keratin plugs & restore sweating
Erythema ab igne
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Persistent erythema or the coarsely reticulated residual
pigmentation resulting from it, due to long exposure to
excessive heat without burn.
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First transient, then permanent
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Legs of women
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May cause epithelial atypia, rarely Bowen’s disease or
squamous cell carcinoma.
3
Cold injuries
Perniosis(=chill blains)
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Cold hypersensitivity
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Erythema & swelling (purple pink) of exposed parts
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Mainly fingers, toes, nose & ears
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Can lead to blistering or ulceration
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Pain, itching & burning
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Cool to touch, onset enhanced by dampness
Treatment
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Protection & prophylaxis of cold
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Quit smoking
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Topical steroids & systemic antihistamines
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Nifidipine 20 mg t.d.s., vasodilators (nicotinamide, dipyridamole)
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Spontaneous resolution occur in 1-3 weeks
Frost bite
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Cold toxicity due to exposure to extremely low temperatures
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Freezing of tissue
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Affected part is pale, waxy, painless
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Different degrees of tissue damage from erythema to deep
gangrene similar to burn
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Degree of damage depends on temperature & duration
Treatment
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Rapid rewarming in hot water bath
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Analgesia: counteract thawing pain
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Supportive measures:
• Bed rest
• High protein/calorie diet
• Wound care
• Avoidance of trauma
Solar injury
The sunlight spectrum is divided into
•
Visible light 400 to 760 nm, has little biologic activity, except for stimulating the
retina
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Infrared radiation beyond 760 nm, experienced as radiant heat.
Below 400 nm is the ultraviolet spectrum, divided into three bands:
-UVA, 320 to 400 nm
-UVB, 290 to 320 nm
-UVC, 200 to 290 nm
Virtually no UVC reaches the earth’s surface, because it is absorbed by the ozone layer.
4
Sun burn
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Normal reaction of skin to sunlight in excess of erythema dose
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Erythema, edema, sometimes blistering on sun exposed skin
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Desquamation follows within a week
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If severe may be accompanied by fever, chills, nausea & hypotension
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Treatment by analgesics, cool compresses, topical steroids
Treatment
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Cool compresses
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Analgesics+ soothing agents
Photosensitivity
Abnormal reaction to normal amount of sunlight
Can be either:
1- chemical photosensitivity: phototoxic & photo allergic photosensitizers
2- metabolic disorders
3- light exacerbated disorders
4- idiopathic phtosensitivity
1- Chemical photosensitivity
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Photosensitizers are substances that may induce an abnormal reaction in skin
exposed to sunlight or its equivalent.
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Substances may be delivered externally or internally.
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Increased sunburn response without prior allergic sensitization is called
phototoxicity. Phototoxicity may occur from both externally applied
phytophotodermatitis or internally administered chemicals phototoxic drug
reaction.
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Photo allergy: needs prior exposure to the substance (sensitization)
Phytophotodermatitis
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Contact between certain plants containing a substance called furocumarine with
moist skin & then exposed to long wave UV (UVA)
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A dermatitis develops followed by intense pigmentation that can last wk.s or m.s
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More in women & children dealing with citrus fruits, & on exposed skin (face &
hands)
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2- Metabolic photosensitivity pellagra & porphyria
Pellagra: Niacin deficiency: 4 D’s disease
Porphyria: Defect in heam synthesis
3- Light exacerbated disorders (Diseases aggravated by sun light exposure)
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1-genetic: xeroderma pigmentosum
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2- acquired: SLE, Darier’s, vitiligo, acne, small % of psoriasis, dermatomyositis,
lichen planus actinicus, & chloasma.
4- idiopathic photosensitivity PLE (polymorphic light
eruption)
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Different morphologies in different people
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Constant morphology in the same patient
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More in young adults, more in females
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Mostly erythematous papular rash on exposed skin
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Starts in spring & improves in summer
Treatment
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Prophylaxis:
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-Avoid sun exposure between 10 am and 2 pm.
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-Barrier protection with hats and clothing.
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-Sunscreen agents include UV-absorbing chemicals (chemical sunscreens:,
and UV-scattering or blocking agents (physical sunscreens).
1- Avoidance: sunscreens with SPF more than 30 with physical & chemical properties
2- Topical steroids: usually potent
3- Systemic antihistamines: to control itching
4-Systemic steroids: in severe cases
5- Antimalarial: as chloroquine
6- Light therapy as PUVA or UVB to induce hardening of the skin
7- Immunosuppressant only in recalcitrant cases: azathioprine & cyclosporin
Mechanical trauma
CALLUS
: circumscribed hyperkeratosis induced by
pressure, diffuse with no central core.
CLAVUS (corn):
circumscribed conical thickenning
with base on surface & apex down pressing on subjacent
structures, of 2 types: Soft corns & hard corn
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Thank you,,,