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)

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5

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1940 1950 1960 1970 1980 1990 2000

Year of birth

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Domestic Water Use (UK)

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40

60

80

100

120

140

160

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1961 1977 1997/1998

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Total Consumption Personal Washing

Bath & Shower Products

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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

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334 213 0

500

1000

1500

2000

2500

3000

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Year

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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