2. Eczema
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Transcript of 2. Eczema
ECZEMA
Dr. Majella E. Lane
What is eczema?
Skin disorder that is characterized by itching, scaling, thickening of the skin, and is usually located on the face, elbows, knees, and arms
Features include
redness of affected areas of skin
generally dry skin, which is often thickened in the areas that have been scratched
lumps or blisters in affected areas
signs of superficial infection such as weeping or crusty deposits.
The Epidermal Barrier
Covalently- Bound lipid
Extension of lamellar granule lipids
Corneo- desmosomes
Keratohyalin granules
Lipid bilayers
Desmosomes
Brick wall model of the skin
Proteolysis of desmosomes
Keratohyalin granules
Lipid bilayers
Proteolysis
Covalently- Bound lipid
Extrusion of lipid lamellae
Desmosomes
desmosomes
Normal Skin
desmosome
Keratinocyte
Lipid lamellae
What causes eczema?
Desquamation of cells from the surface is the key to
maintaining normal skin barrier function
Desquamation is caused by stratum corneum
chymotryptic enzyme (SCCE).
This 27-kDa protein is thought to be packaged in the
lamellar bodies of the stratum granulosum.
As a proenzmye present in the whole SC
SCCE is associated with the desmosomes where it
hydrolyzes the structure to initiate desquamation
Cell Cell
Proteases
SCCE
Inhibitors
Homeostasis of barrier
SCCE
NMF
Water
NMF
Water
Normal skin barrier
What causes eczema?
INCREASED BREAKDOWN OF SKIN BARRIER
ASSOCIATED WITH THE FOLLOWING:
– Genetic factors
– Alteration of the immune system
– Environmental contributors (Soap and
detergents, Hard water, House dust mite, Dietary
allergens)
– Aggravating factors
Gene Environment
Increased mRNA stability
Increase in mRNA translation
Increased SCCE Activity
Change in SCCE gene in
atopic eczema
Change in protease gene in atopic eczema
Vasilopoulos Y et al. J Invest Dermatol 2004;123:62–6
Environmental factors - Prevalence of Atopic Eczema
(4)
(1)
(1)
(1)
(3)
(3)
(2)*
0
5
10
15
20
25
30
1940 1950 1960 1970 1980 1990 2000
Year of birth
% o
f C
hil
dre
n
Domestic Water Use (UK)
0
20
40
60
80
100
120
140
160
180
1961 1977 1997/1998
Year
Do
mesti
c W
ate
r C
on
su
mp
tio
n
Lit
res / H
ead
/ D
ay
Total Consumption Personal Washing
Bath & Shower Products
1 2 3
453
173
76
Year
0
50
100
150
200
250
300
350
400
450
500
£ M
illio
ns
1981 1991 2001
UK Retail Sales
0%
20%
40%
60%
80%
100%
1940 1980 1995 1998
Homes with central heating 1940 - 2000
Carpets & other Floor Coverings
3251
2154
1176
334 213 0
500
1000
1500
2000
2500
3000
3500
Year
£ M
illio
ns
1963 1970 1980 1990 2000
UK Expenditure
Dust Mite
NMF
Water
NMF
Water
SCCE
SOAP
pH
Use of harsh soap leads to dry skin
Types of eczema
Irritant – Direct skin reaction against irritant substance
Allergic contact - Immune response, delayed
Atopic – allergic type often seen in people who have asthma/hay fever
Seborrheic - in infants appears in nappy area and the scalp. In adults, also appears on the scalp and in the skin creases between the nose and sides of the mouth. Can be caused by yeast infection.
Venous – Caused by varicose veins
Discoid – appears as “islands” of eczema on normal skin
Different types may co-exist
Lichenification (Thickening) due to scratching and rubbing, may complicate any chronic eczema
Atopic eczema is the most common type and it usually involves dry skin as well as infection and lichenification
Symptoms
Itch – essential symptom but not specific
Nerve fibres transmit itch sensation from skin, ultimately
connected to the spinal cord and brain
Redness
When skin is inflamed the local network of blood vessels widens,
increasing the flow of blood and making it red.
Inflammation in eczema can be triggered by a range of factors.
Important factor = bacterial infection which causes increase in
redness and heat from the tissues
Thickening – protective response to scratching
Blisters - less adhesion of skin cells and/or infection
Crusts – high protein content in fluid from infected skin
Immune response Normal Epidermal Barrier - At Birth
TH1 TH2 TH-0
Allergens
Normal Epidermal Barrier - At 6 Months
TH1 TH2 TH-0
Allergens
TH1 TH2 TH-0
Weakened
corneodesmosomes
+VE
Defective Epidermal Barrier - Birth
TH1 TH2 TH-0
Low allergen
exposure
+VE
Defective Epidermal Barrier - Birth
Defective Epidermal Barrier - 6 Mo
TH1 TH2 TH-0
Low allergen
exposure
+VE
TH1
TH2
TH-0
High allergen
exposure
+VE
Defective Epidermal Barrier - 6 Mo
TH1 TH2 TH-0
Allergens
Irritants
Soap
Drugs
pH
Gene Environment Interactions in AD
Allergen
Management of eczema
Removal or treatment of contributory factors
including occupational and domestic irritants
Known or suspected contact allergens should be
avoided
Rarely, ingredients in topical medicinal products
may sensitise the skin
BNF lists active ingredients together with excipients
that have been associated with skin sensitisation.
Emollients
Aqeous Cream - emulsifying ointment 30%, phenoxyethanol 1% in freshly boiled and cooled purified water NOT FOR USE AS A MOISTURISER!!!!
Emulsifying Ointment -emulsifying wax 30%, white soft paraffin 50%, liquid paraffin 20%
Hydrous ointment - dried magnesium sulphate 0.5%, phenoxyethanol 1%, wool alcohols ointment 50%, in freshly boiled and cooled purified water
Liquid and white soft paraffin ointment - liquid paraffin 50%, white soft paraffin 50%
White soft paraffin – white petroleum jelly
Yellow soft paraffin – yellow petroleum jelly
Other emollients
Preparations containing urea which is a hydrating
material (Balneum Plus, Calmurid)
Emollients with disinfectants (Benzalkonium
chloride)
Bath additives (Balneum = soya oil )
Topical corticosteroids
Mild - used on face and flexures
Examples - Hydrocortisone
Moderate - Clobetasone
Potent used on discoid/lichenified eczema, scalp, limbs
and trunk
- Betamethasone
Can be combined with antifungals, disinfectants
Bandages (including those containing zinc and
ichthammol) sometimes applied over topical
corticosteroids to treat eczema of the limbs
Topical corticosteroids
Management of other features of eczema
Coal tar and ichthammol may be useful for chronic
cases
Antihistamines may be of value for itch particularly
because of sedative effect
Potassium permanganate useful in exudative
eczema
Sebhorraeic dermatitis treated with ketoconazole,
coal tar shampoos and mild corticosteroid/antiseptic
preparations
Drugs affecting the immune response
Ciclosporin (cyclosporin)
Azathioprine
Mycophenolate mofetil
Methotrexate
Pimecrolimus, tacrolimus
Block T cell synthesis or activation thus no immune
response